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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	May 31, 2016	Aug. 05, 2016	Nov. 30, 2015
Document and Entity Information
Entity Registrant Name	Mistras Group, Inc.
Entity Central Index Key	0001436126
Document Type	10-K
Document Period End Date	May 31, 2016
Amendment Flag	false
Current Fiscal Year End Date	--05-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 364.4
Entity Common Stock, Shares Outstanding		28,955,455
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($) $ in Thousands	May 31, 2016	May 31, 2015
Current Assets
Cash and cash equivalents	$ 21,188	$ 10,555
Accounts receivable, net	137,913	133,228
Inventories	9,918	10,841
Deferred income taxes	6,216	5,144
Prepaid expenses and other current assets	12,711	11,698
Total current assets	187,946	171,466
Property, plant and equipment, net	78,676	79,256
Intangible assets, net	43,492	51,276
Goodwill	169,220	166,414
Deferred income taxes	1,000	1,208
Other assets	2,341	2,107
Total Assets	482,675	471,727
Current Liabilities
Accounts payable	10,796	10,529
Accrued expenses and other current liabilities	62,983	55,914
Current portion of long-term debt	12,553	17,902
Current portion of capital lease obligations	7,835	8,646
Income taxes payable	2,710	532
Total current liabilities	96,877	93,523
Long-term debt, net of current portion	72,456	95,557
Obligations under capital leases, net of current portion	11,932	10,717
Deferred income taxes	18,328	16,984
Other long-term liabilities	6,794	9,934
Total Liabilities	206,387	226,715
Commitments and contingencies
Equity
Preferred stock, 10,000,000 shares authorized	0	0
Common stock, $0.01 par value, 200,000,000 shares authorized, 28,939,993 and 28,703,320 shares issued and outstanding as of May 31, 2016 and May 31, 2015, respectively	290	287
Additional paid-in capital	213,737	208,064
Retained earnings	82,235	57,581
Accumulated other comprehensive loss	(20,099)	(21,113)
Total Mistras Group, Inc. stockholders’ equity	276,163	244,819
Noncontrolling interests	125	193
Total Equity	276,288	245,012
Total Liabilities and Equity	$ 482,675	$ 471,727

Consolidated Balance Sheets (Parenthetical) - $ / shares	May 31, 2016	May 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	28,939,993	28,703,320
Common stock, shares outstanding (in shares)	28,939,993	28,703,320

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Income Statement [Abstract]
Revenue	$ 719,181	$ 711,252	$ 623,447
Cost of revenue	494,911	506,281	432,695
Depreciation	21,262	20,238	17,809
Gross profit	203,008	184,733	172,943
Selling, general and administrative expenses	141,229	143,978	123,690
Research and engineering	2,523	2,521	2,995
Depreciation and amortization	11,212	13,048	10,620
Acquisition-related (benefit) expense, net	(1,453)	(5,167)	(2,657)
Legal settlement	6,320	0	0
Income from operations	43,177	30,353	38,295
Interest expense	4,762	4,622	3,192
Income before provision for income taxes	38,415	25,731	35,103
Provision for income taxes	13,765	9,740	12,528
Net income	24,650	15,991	22,575
Less: net (loss) income attributable to noncontrolling interests, net of taxes	(4)	(90)	57
Net income attributable to Mistras Group, Inc.	$ 24,654	$ 16,081	$ 22,518
Earnings per common share
Basic (in dollars per share)	$ 0.85	$ 0.56	$ 0.79
Diluted (in dollars per share)	$ 0.82	$ 0.54	$ 0.77
Weighted average common shares outstanding:
Basic (in shares)	28,856	28,613	28,365
Diluted (in shares)	29,891	29,590	29,324

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 24,650	$ 15,991	$ 22,575
Other comprehensive income (loss):
Foreign currency translation adjustments	1,014	(19,602)	2,941
Comprehensive income (loss)	25,664	(3,611)	25,516
Less: net (loss) income attributable to noncontrolling interests	(4)	(90)	57
Foreign currency translation adjustments attributable to noncontrolling interests	1	5	(4)
Comprehensive income (loss) attributable to Mistras Group, Inc.	$ 25,669	$ (3,516)	$ 25,455

Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Total Mistras Group, Inc. Stockholders’ Equity	Common Stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss)	Noncontrolling Interest
Balance at May. 31, 2013	$ 210,280	$ 210,053	$ 282	$ 195,241	$ 18,982	$ (4,452)	$ 227
Balance (in shares) at May. 31, 2013			28,211
Increase (Decrease) in Stockholders' Equity
Net income	22,575	22,518			22,518		57
Other comprehensive (income) loss, net of tax	2,945	2,941				2,941	4
Share-based payments	6,261	6,261		6,261
Share-based payments (in shares)			19
Net settlement on vesting of restricted stock units	(1,006)	(1,006)	$ 1	(1,007)
Net settlement on vesting of restricted stock units (in shares)			123
Excess tax benefit from share-based payment compensation	340	340		340
Exercise of stock options	997	997	$ 1	996
Exercise of stock options (in shares)			103
Balance at May. 31, 2014	242,392	242,104	$ 284	201,831	41,500	(1,511)	288
Balance (in shares) at May. 31, 2014			28,456
Increase (Decrease) in Stockholders' Equity
Net income	15,991	16,081			16,081		(90)
Other comprehensive (income) loss, net of tax	(19,607)	(19,602)				(19,602)	(5)
Share-based payments	6,579	6,579		6,579
Share-based payments (in shares)			21
Net settlement on vesting of restricted stock units	(1,481)	(1,481)	$ 2	(1,483)
Net settlement on vesting of restricted stock units (in shares)			161
Excess tax benefit from share-based payment compensation	388	388		388
Exercise of stock options	750	750	$ 1	749
Exercise of stock options (in shares)			65
Balance at May. 31, 2015	245,012	244,819	$ 287	208,064	57,581	(21,113)	193
Balance (in shares) at May. 31, 2015			28,703
Increase (Decrease) in Stockholders' Equity
Net income	24,650	24,654			24,654		(4)
Other comprehensive (income) loss, net of tax	950	1,014				1,014	(64)
Share-based payments	6,394	6,394		6,394
Net settlement on vesting of restricted stock units	(1,091)	(1,091)	$ 2	(1,093)
Net settlement on vesting of restricted stock units (in shares)			182
Excess tax benefit from share-based payment compensation	(170)	(170)		(170)
Exercise of stock options	543	543	$ 1	542
Exercise of stock options (in shares)			55
Balance at May. 31, 2016	$ 276,288	$ 276,163	$ 290	$ 213,737	$ 82,235	$ (20,099)	$ 125
Balance (in shares) at May. 31, 2016			28,940

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Cash flows from operating activities
Net income	$ 24,650	$ 15,991	$ 22,575
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	32,474	33,286	28,429
Deferred income taxes	240	(1,745)	(621)
Share-based compensation expense	6,514	6,579	6,261
Charges associated with the exit of foreign operations	0	2,516	0
Fair value adjustments to contingent consideration	(2,066)	(5,382)	(3,937)
Other	(1,052)	1,647	617
Changes in operating assets and liabilities, net of effect of acquisitions
Accounts receivable	(4,999)	3,982	(23,857)
Inventories	1,595	388	1,203
Prepaid expenses and other current assets	(1,128)	(288)	(4,059)
Other assets	(684)	(821)	36
Accounts payable	254	(6,571)	6,125
Accrued expenses and other liabilities	10,187	2,006	4,532
Income taxes payable	2,139	(1,748)	(431)
Net cash provided by operating activities	68,124	49,840	36,873
Cash flows from investing activities
Purchase of property, plant and equipment	(14,864)	(15,104)	(16,871)
Purchase of intangible assets	(1,315)	(866)	(708)
Acquisition of businesses, net of cash acquired	(1,743)	(34,677)	(21,924)
Proceeds from sale of equipment	1,170	996	1,498
Net cash used in investing activities	(16,752)	(49,651)	(38,005)
Cash flows from financing activities
Repayment of capital lease obligations	(7,870)	(8,653)	(8,139)
Proceeds from borrowings of long-term debt	2,737	2,232	0
Repayment of long-term debt	(17,580)	(11,457)	(8,830)
Proceeds from revolver	55,800	110,300	102,880
Repayments of revolver	(69,600)	(86,800)	(81,300)
Payment of contingent consideration for business acquisitions	(3,147)	(3,213)	(1,678)
Taxes paid related to net share settlement of equity awards	(1,091)	(1,481)	(1,007)
Excess tax benefit from share-based payment compensation	(170)	388	340
Proceeds from the exercise of stock options	543	750	996
Net cash (used in) provided by financing activities	(40,378)	2,066	3,262
Effect of exchange rate changes on cash and cash equivalents	(361)	(1,720)	88
Net change in cash and cash equivalents	10,633	535	2,218
Cash and cash equivalents:
Beginning of period	10,555	10,020	7,802
End of period	21,188	10,555	10,020
Supplemental disclosure of cash paid
Interest	4,151	4,504	3,271
Income taxes	10,686	13,243	12,920
Noncash investing and financing
Equipment acquired through capital lease obligations	8,248	8,031	11,031
Issuance of notes payable and other debt obligations primarily related to acquisitions	$ 0	$ 20,480	$ 336

Description of Business and Basis of Presentation

12 Months Ended

May 31, 2016

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Description of Business and Basis of Presentation

Description of Business

Mistras Group, Inc. and subsidiaries (the Company) is a leading “one source” global provider of technology-enabled asset protection solutions used to evaluate the structural integrity and reliability of critical energy, industrial and public infrastructure. The Company combines industry-leading products and technologies, expertise in mechanical integrity (MI) and non-destructive testing (NDT) services and proprietary data analysis software to deliver a comprehensive portfolio of customized solutions, ranging from routine inspections to complex, plant-wide asset integrity assessments and management. These mission critical solutions enhance customers’ ability to extend the useful life of their assets, increase productivity, minimize repair costs, comply with governmental safety and environmental regulations, manage risk and avoid catastrophic disasters. The Company serves a global customer base of companies with asset-intensive infrastructure, including companies in the oil and gas, fossil and nuclear power, alternative and renewable energy, public infrastructure, chemicals, commercial aerospace and defense, transportation, primary metals and metalworking, pharmaceutical/biotechnology and food processing industries and research and engineering institutions.

Principles of Consolidation

The accompanying audited consolidated financial statements include the accounts of Mistras Group, Inc. and its wholly and majority-owned subsidiaries. For subsidiaries in which the Company’s ownership interest is less than 100%, the noncontrolling interests are reported in stockholders’ equity in the accompanying consolidated balance sheets. The noncontrolling interests in net income, net of tax, is classified separately in the accompanying consolidated statements of income.

All significant intercompany accounts and transactions have been eliminated in consolidation. Mistras Group, Inc.’s and its subsidiaries’ fiscal years end on May 31 except for the subsidiaries in the International segment, which end on April 30. Accordingly, the Company’s International segment subsidiaries are consolidated on a one-month lag. Therefore, in the quarter and year of acquisition, results of acquired subsidiaries in the International segment are generally included in consolidated results for one less month than the actual number of months from the acquisition date to the end of the reporting period. Management does not believe that any events occurred during the one-month lag period that would have a material effect on the Company’s consolidated financial statements for fiscal 2016. As discussed in Note 7 - Acquisitions and Dispositions, during the lag period in fiscal 2015, the Company sold an international subsidiary, and decided to sell two additional international subsidiaries. Management does not believe that any additional events occurred during the fiscal 2015 one-month lag period that would have a material effect on the Company’s consolidated financial statements. Reference to a fiscal year means the fiscal year ended May 31.

Reclassifications

Certain amounts in prior periods have been reclassified to conform to the current year presentation. Such reclassifications did not have a material effect on the Company's financial condition or results of operations as previously reported.

Immaterial Correction

Subsequent to the issuance of its consolidated financial statements as of and for the year ended May 31, 2015, the Company identified errors related to the classification of amounts reported in the Consolidated Statement of Cash Flows for that period. In accordance with the SEC Staff Accounting Bulletin (SAB) No. 99, Materiality, and SAB No. 108, Considering the Effects of Prior Year Misstatements when Quantifying Misstatements in Current Year Financial Statements, management evaluated the materiality of the errors from qualitative and quantitative perspectives, and concluded that the errors were immaterial. Accordingly, management has corrected the presentation of the affected line items of the accompanying Consolidated Statement of Cash Flows for the year ended May 31, 2015, as summarized below. These changes did not impact the Company’s net income, balance sheet, or stockholders’ equity for any periods previously reported.



	Previously Reported		Revised
Cash flows from operating activities
Accounts payable	(6,281	)	(6,571	)
Accrued expenses and other liabilities	2,500		2,006
Net cash provided by operating activities	50,624		49,840

Cash flows from investing activities
Acquisition of businesses, net of cash acquired	(34,967	)	(34,677	)
Net cash used in investing activities	(49,941	)	(49,651	)

Cash flows from financing activities
Proceeds from borrowings of long-term debt	—		2,232
Repayments of long-term debt	(9,224	)	(11,457	)
Net borrowings against revolver	21,914		23,500
Net cash provided by financing activities	481		2,066

Effect of exchange rate changes on cash and cash equivalents	(629	)	(1,720	)

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	May 31, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Revenue Recognition Revenue is generally recognized when persuasive evidence of an arrangement exists, services have been rendered or products have been delivered, the fee is fixed or determinable, and collectability is reasonably assured. Shipping and handling costs are included in cost of revenues. Taxes collected from customers and remitted to governmental authorities are presented in the consolidated statements of income on a net basis. One customer accounted for 10% of our revenues in fiscal 2016, which primarily were generated from the Services segment. No customer accounted for 10% or more of our revenues in fiscal 2015 and 2014. The following revenue recognition policies define the manner in which we account for specific transaction types: Services Revenue is primarily derived from providing services on a time and material basis. Service arrangements generally consist of inspection professionals working under contract for a fixed period of time or on a specific customer project. Revenue is generally recognized when the service is performed in accordance with terms of each customer arrangement, upon completion of the earnings process and when collection is reasonably assured. At the end of any reporting period, revenue is accrued for services that have been earned which have not yet been billed. Reimbursable costs, including those related to travel and out-of-pocket expenses, are included in revenue, and equivalent amounts of reimbursable costs are included in cost of services. Products and Systems Sales of products and systems are recorded when the sales price is fixed and determinable and the risks and rewards of ownership are transferred (generally upon shipment) and when collectability is reasonably assured. These arrangements occasionally contain multiple elements or deliverables, such as hardware, software (that is essential to the functionality of the hardware) and related services. The Company recognizes revenue for delivered elements as separate units of accounting, when the delivered elements have standalone value, uncertainties regarding customer acceptance are resolved and there are no refund or return rights for the delivered elements. The Company establishes the selling prices for each deliverable based on its, vendor-specific objective evidence (“VSOE”), if available, third-party evidence, if VSOE is not available, or estimated selling price (“ESP”) if neither VSOE nor third-party evidence is available. The Company establishes VSOE of selling price using the price charged for a deliverable when sold separately and, in rare instances, using the price established by management having the relevant authority. Third-party evidence of selling price is established by evaluating largely similar and interchangeable competitor products or services in standalone sales to similarly situated customers. The Company determines ESP, by considering Internal factors such as margin objectives, pricing practices and controls, customer segment pricing strategies and the product life cycle. Consideration is also given to market conditions such as competitor pricing strategies and Industry technology life cycles. When determining ESP, the Company applies management judgment to establish margin objectives and pricing strategies and to evaluate market conditions and product life cycles. Changes in the aforementioned factors may result in a different allocation of revenue to the deliverables in multiple element arrangements and therefore may change the pattern and timing of revenue recognition for these elements, but will not change the total revenue recognized for the arrangement. A portion of the Company’s revenue is generated from engineering and manufacturing of custom products under long-term contracts that may last from several months to several years, depending on the contract. Revenues from long-term contracts are recognized on the percentage-of-completion method of accounting. Under the percentage-of-completion method of accounting revenues are recognized as work is performed. The percentage of completion at any point in time is generally based on total costs or total labor dollars incurred to date in relation to the total estimated costs or total labor dollars estimated at completion. The percentage of completion is then applied to the total contract revenue to determine the amount of revenue to be recognized in the period. Application of the percentage-of-completion method of accounting requires the use of estimates of costs to be incurred for the performance of the contract. Contract costs include all direct materials, direct labor costs and those indirect costs related to contract performance, such as indirect labor, supplies, tools, repairs, and all costs associated with operation of equipment. The cost estimation process is based upon the professional knowledge and experience of our engineers, project managers and financial professionals. Factors that are considered in estimating the work to be completed include the availability and productivity of labor, the nature and complexity of the work to be performed, the effect of change orders, the availability of materials, the effect of any delays in our project performance and the recoverability of any claims. Whenever revisions of estimated contract costs and contract values indicate that the contract costs will exceed estimated revenues, thus creating a loss, a provision for the total estimated loss is recorded in that period. Use of Estimates The preparation of financial statements in accordance with generally accepted accounting principles requires that the Company make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses and disclosure of contingent assets and liabilities at the date of financial statements. The accounting policies that the Company believes require more significant estimates and assumptions include: revenue recognition, valuations of accounts receivable, long lived assets, goodwill, and deferred tax assets and uncertain tax positions. The Company bases its estimates and assumptions on historical experience, known or expected trends and various other assumptions that it believes to be reasonable. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates, which may cause the Company’s future results to be significantly affected. Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Accounts Receivable Accounts receivable are stated net of an allowance for doubtful accounts and sales allowances. Outstanding accounts receivable balances are reviewed periodically, and allowances are provided at such time that management believes it is probable that such balances will not be collected within a reasonable period of time. The Company extends credit to its customers based upon credit evaluations in the normal course of business, primarily with 30-day terms. Bad debts are provided for based on historical experience and management’s evaluation of outstanding accounts receivable. Accounts are generally written off when they are deemed uncollectible. One customer accounted for 11% of our accounts receivable in fiscal 2016. No customer accounted for 10% or more of our accounts receivable in fiscal 2015. Inventories Inventories are stated at the lower of cost, as determined by using the first-in, first-out method, or market. Work in process and finished goods inventory include material, direct labor, variable costs and overhead. Purchased and Internal-Use Software The Company capitalizes certain costs that are incurred to purchase or to create and implement internal-use software, which includes software coding, installation and testing. Capitalized costs are amortized on a straight-line basis over three years, the estimated useful life of the software. Property, Plant and Equipment Property, plant and equipment are recorded at cost. Depreciation of property, plant and equipment is computed utilizing the straight-line method over the estimated useful lives of the assets. Amortization of leasehold improvements is computed utilizing the straight-line method over the shorter of the remaining lease term or estimated useful life. Repairs and maintenance costs are expensed as incurred. Goodwill Goodwill represents the excess purchase price of acquired businesses over the fair values attributed to underlying net tangible assets and identifiable intangible assets. The Company tests the carrying value of goodwill for impairment at a “reporting unit” level (which for the Company is represented by (i) our Services segment, (ii) our Products and Systems segment, and (iii) the European component and (iv) Brazilian component of our International segment), using a qualitative assessment for its Services reporting unit and a two-step approach for its remaining reporting units, annually as of March 1, or whenever an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. If the fair value of a reporting unit is less than its carrying value, this is an indicator that the goodwill assigned to that reporting unit may be impaired. In this case, a second step is performed to allocate the fair value of the reporting unit to the assets and liabilities of the reporting unit as if it had just been acquired in a business combination, and as if the purchase price was equivalent to the fair value of the reporting unit. The excess of the fair value of the reporting unit over the amounts assigned to its assets and liabilities is referred to as the implied fair value of goodwill. The implied fair value of the reporting unit’s goodwill is then compared to the actual carrying value of goodwill. If the implied fair value is less than the carrying value, an impairment loss would be recorded to reduce the carrying value of goodwill to its implied fair value. The Company considers the income and market approaches to estimating the fair value of our reporting units, which requires significant judgment in evaluation of economic and industry trends, estimated future cash flows, discount rates and other factors. The Company believes that the fair values of each of its reporting units are substantially in excess of their respective carrying amounts. Significant deterioration in industry or economic trends, disruptions to our business, inability to effectively integrate acquired businesses, or other factors, may cause these fair value to decline, possibly resulting in impairment charges to goodwill in future periods. Impairment of Long-lived Assets The Company reviews the recoverability of its long-lived assets on a periodic basis in order to identify indicators of a possible impairment. The assessment for potential impairment is based primarily on the Company’s ability to recover the carrying value of its long-lived assets from expected future undiscounted cash flows. If the total expected future undiscounted cash flows are less than the carrying amount of the assets, a loss is recognized for the difference between fair value (computed based upon the expected future discounted cash flows) and the carrying value of the assets. Research and Engineering Research and product development costs are expensed as incurred. Advertising, Promotions and Marketing The costs for advertising, promotion and marketing programs are expensed as incurred and are included in selling, general and administrative expenses. Advertising expense was approximately $1.8 million, $2.2 million and $1.8 million for fiscal 2016, 2015 and 2014, respectively. Fair Value of Financial Instruments The carrying amounts of cash and cash equivalents, accounts receivable, accounts payable and other financial current assets and liabilities approximate fair value based on the short-term nature of the items. The carrying value of long-term debt approximates fair value due to the variable-rate structure of the debt. The fair value of the Company’s notes payable and capital lease obligations approximate their carrying amounts as those obligations bear interest at rates which management believes would currently be available to the Company for similar obligations. Foreign Currency Translation The financial position and results of operations of the Company’s foreign subsidiaries are measured using their functional currencies, which, is their local currency. Assets and liabilities of foreign subsidiaries are translated into the U.S. Dollar at the exchange rates in effect at the balance sheet date. Income and expenses are translated at the average exchange rate during the period. Translation gains and losses are reported as a component of other comprehensive income (loss) for the period and included in accumulated other comprehensive income (loss) within stockholders’ equity. Foreign currency (gains) and losses arising from transactions denominated in currencies other than the functional currency are included in net income, reported in SG&A expenses, and were approximately $(0.1) million, $1.5 million and $0.1 million in fiscal 2016, 2015 and 2014, respectively. Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents and accounts receivable. At times, cash deposits may exceed the limits insured by the Federal Deposit Insurance Corporation. The Company believes it is not exposed to any significant credit risk or risk of nonperformance of financial institutions. Self-Insurance The Company is self-insured for certain losses relating to workers’ compensation and health benefits claims. The Company maintains third-party excess insurance coverage for all workers compensation and health benefit claims in excess of approximately $0.3 million to reduce its exposure from such claims. Self-insured losses are accrued when it is probable that an uninsured claim has been incurred but not reported and the amount of the loss can be reasonably estimated at the balance sheet date. Share-based Compensation The value of services received from employees and directors in exchange for an award of an equity instrument is measured based on the grant-date fair value of the award. The computed value is recognized as a non-cash cost on a straight-line basis over the period the individual provides services, which is typically the vesting period of the award with the exception of awards containing an internal performance measure which is recognized on a straight-line basis over the vesting period subject to the probability of meeting the performance requirements and adjusted for the number of shares expected to be earned. As share-based compensation expense is based on awards ultimately expected to vest, the amount of expense has been reduced for estimated forfeitures. The cost of these awards is recorded in selling, general and administrative expense in the company’s consolidated statements of income. Income Taxes Income taxes are accounted for under the asset and liability method. Deferred income tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and tax credit carry-forwards. Deferred income tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred income tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A valuation allowance is provided if it is more likely than not that some or all of a deferred income tax asset will not be realized. Financial accounting standards prescribe a minimum recognition threshold a tax position is required to meet before being recognized in the financial statements. These standards also provide guidance on de-recognition, measurement, and classification of amounts relating to uncertain tax positions, accounting for and disclosure of interest and penalties, accounting in interim periods and disclosures required. Interest and penalties related to unrecognized tax positions are recognized as incurred within “provision for income taxes” in the consolidated statements of income. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU No. 2014-09, Revenue from Contracts with Customers, which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The ASU will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. The new standard is effective for fiscal years and interim periods within those fiscal years beginning December 15, 2017, as a result of a one year deferral in the standard issued by the FASB in August 2015 with ASU 2015-14, Revenue from Contracts with Customers - Deferral of the Effective Date. Early application is not permitted. The standard permits the use of either the retrospective or cumulative effect transition method. The Company is evaluating the effect that ASU 2014-09 will have on its consolidated financial statements and related disclosures. In September 2015, the FASB issued ASU No. 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments. This amendment will simplify the accounting for adjustments made to provisional amounts recognized in a business combination and eliminates the requirement to retrospectively account for those adjustments in previous reporting periods. This update will require on the face of the income statement or in the notes to the financial statements the amount recorded in current-period earnings that would have previously been recorded if the adjustment to the provisional amounts had been recognized as of the acquisition date. ASU 2015-16 is effective for fiscal years, and interim periods within those fiscal years beginning after December 15, 2015. This update should be applied prospectively and earlier adoption is permitted for financial statements that have not been issued. The Company is evaluating the effect that ASU 2015-16 will have on its consolidated financial statements and related disclosures. In November 2015, the FASB issued ASU No. 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes. This amendment will simplify the presentation of deferred tax assets and liabilities on the balance sheet and require all deferred tax assets and liabilities to be treated as non-current. ASU 2015-17 is effective for fiscal years, and interim periods within those fiscal years beginning after December 15, 2016, with early adoption permitted. The Company is evaluating the effect that ASU 2015-17 will have on its consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). This amendment supersedes previous accounting guidance (Topic 840) and requires all leases, with exception of leases with a term of 12 months or less, to be recorded on the balance sheet as lease assets and lease liabilities. ASU 2016-02 is effective for fiscal years, and interim periods within those fiscal years beginning after December 15, 2018, with early adoption permitted. The standard requires lessees and lessors to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. The Company is evaluating the effect that ASU 2016-02 will have on its consolidated financial statements and related disclosures. In March 2016, the FASB issues ASU No. 2016-09, Stock Compensation (Topic 718). This amendment will simplify certain aspects of accounting for share-based payment transactions, which include accounting for income taxes and the related impact on the statement of cash flows, an option to account for forfeitures when they occur in addition to the existing guidance to estimate the forfeitures of awards, classification of awards as either equity or liabilities and classification on the statement of cash flows for employee taxes paid to tax authorities on shares withheld for vesting. ASU 2016-09 is effective for fiscal years, and interim periods within those fiscal years beginning after December 15, 2016, with early adoption permitted. The Company is evaluating the effect that ASU 2016-09 will have on its consolidated financial statements and related disclosures.

Earnings per Share

12 Months Ended

May 31, 2016

Earnings Per Share [Abstract]

Earnings per Share

Basic earnings per share is computed by dividing net income attributable to common shareholders by the weighted average number of shares outstanding during the period. Diluted earnings per share is computed by dividing net income attributable to common shareholders by the sum of (1) the weighted average number of shares of common stock outstanding during the period, and (2) the dilutive effect of assumed conversion of equity awards using the treasury stock method. With respect to the number of weighted average shares outstanding (denominator), diluted shares reflects: (i) only the exercise of options to acquire common stock to the extent that the options’ exercise prices are less than the average market price of common shares during the period and (ii) the pro forma vesting of restricted stock units.

The following table sets forth the computations of basic and diluted earnings per share:



	For the year ended May 31,
	2016		2015		2014
Basic earnings per share
Numerator:
Net income attributable to Mistras Group, Inc.	$	24,654	$	16,081	$	22,518
Denominator
Weighted average common shares outstanding	28,856		28,613		28,365
Basic earnings per share	$	0.85	$	0.56	$	0.79

Diluted earnings per share:
Numerator:
Net income attributable to Mistras Group, Inc.	$	24,654	$	16,081	$	22,518
Denominator
Weighted average common shares outstanding	28,856		28,613		28,365
Dilutive effect of stock options outstanding	712		719		775
Dilutive effect of restricted stock units outstanding	323		258		184
	29,891		29,590		29,324
Diluted earnings per share	$	0.82	$	0.54	$	0.77

The following potential common shares were excluded from the computation of diluted earnings per share, as the effect would have been anti-dilutive:



	For the year ended May 31,
	2016	2015	2014
Potential common stock attributable to stock options outstanding	5	6	5
Potential common stock attributable to performance awards outstanding	24	1	121
Total	29	7	126

Accounts Receivable, net

12 Months Ended

May 31, 2016

Receivables [Abstract]

Accounts Receivable, net

Accounts receivable consist of the following:



	May 31,
	2016			2015
Trade accounts receivable	$	140,820		$	136,208
Allowance for doubtful accounts	(2,907		)	(2,980		)
Accounts receivable, net	$	137,913		$	133,228

The Company had $18.8 million and $15.0 million of unbilled revenues accrued as of May 31, 2016 and 2015, respectively. Unbilled revenues as of May 31, 2016 are expected to be billed in the first quarter of fiscal 2017.

Inventories

12 Months Ended

May 31, 2016

Inventory Disclosure [Abstract]

Inventories

Inventories consist of the following:



	May 31,
	2016		2015
Raw materials	$	3,827	$	4,194
Work in progress	1,743		1,604
Finished goods	2,839		3,178
Services-related consumable supplies	1,509		1,865
Inventory	$	9,918	$	10,841

Property, Plant and Equipment, net

12 Months Ended

May 31, 2016

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment, net

Property, plant and equipment consist of the following:



	May 31,
	Useful Life	2016			2015
	(Years)
Land		$	1,735		$	1,856
Building and improvements	30-40	19,364			17,712
Office furniture and equipment	5-8	8,692			7,934
Machinery and equipment	5-7	173,053			162,762
		202,844			190,264
Accumulated depreciation and amortization		(124,168		)	(111,008		)
Property, plant and equipment, net		$	78,676		$	79,256

Depreciation expense was approximately $22.9 million, $22.2 million and $19.2 million for the years ended May 31, 2016, 2015 and 2014, respectively.

Acquisitions and Dispositions

12 Months Ended

May 31, 2016

Business Combinations [Abstract]

Acquisitions and Dispositions

Acquisitions

During fiscal 2016, the Company completed two acquisitions. The Company purchased a U.S.-based company that provides unmanned aerial systems and NDT services and a Canadian-based company that provides engineering and NDT services. In these acquisitions, the Company acquired 100% of the common stock of each acquiree in exchange for aggregate consideration of $1.8 million in cash and contingent consideration estimated to be $1.0 million to be earned based upon the acquired business achieving specific performance metrics over various periods during the initial four years of operations from the acquisition date. The Company accounted for these transactions in accordance with the acquisition method of accounting for business combinations. The estimated total potential contingent consideration for these acquisitions ranges from zero to $0.3 million as of May 31, 2016.

During fiscal 2015, the Company completed the acquisition of four companies. One of the acquired companies is located in the U.S. and provides maintenance and inspection services primarily on offshore platforms. This acquisition expanded the service offerings within the Services segment, allowing the Company to provide services to the upstream operations of its customers. The Company also purchased a group of asset protection businesses located in Quebec, Canada and an asset inspection business in Florida to complement service offerings within the Company’s Services segment and continue its market expansion strategy. The Company’s International Segment completed an acquisition of an asset inspection business located in the United Kingdom. In these acquisitions, the Company acquired 100% of the common stock or certain assets of each acquiree in exchange for aggregate consideration of approximately $35.8 million in cash and $20.5 million in notes payable over two years. The Company accounted for such transactions in accordance with the acquisition method of accounting for business combinations. In addition to the cash consideration related to these acquisitions, the Company accrued a liability of approximately $2.3 million, which represents the estimated fair value of contingent consideration expected to be payable in the event that the acquired companies achieve specific performance metrics during various periods over the next three years of operations. The estimated total potential contingent consideration for these acquisitions ranges from zero to $3.2 million as of May 31, 2015.

Assets and liabilities of the acquired businesses were included in the consolidated balance sheets as of May 31, 2016 based on their estimated fair value on the date of acquisition as determined in a purchase price allocation, using available information and making assumptions management believes are reasonable. The results of operations of each of the acquisitions completed in fiscal 2016 and 2015 are included in each respective operating segment’s results of operations from the date of acquisition. The Company’s allocation of purchase price for these acquisitions is included in the table below. The following table summarizes the estimated fair value of the assets acquired and liabilities assumed and any subsequent adjustments made during the fiscal year ended May 31, 2016:



	2016			2015
Number of entities	2			4

Cash paid	$	1,784		$	35,755
Subordinated notes issued	—			20,505
Contingent consideration	991			2,255
Consideration paid	$	2,775		$	58,515

Current net assets	$	180		$	2,770
Debt and other long-term liabilities	(546		)	(5,889		)
Property, plant and equipment	485			7,395
Deferred tax liability	(72		)	(2,467		)
Intangibles	—			10,394
Goodwill	2,728			46,312
Net assets acquired	$	2,775		$	58,515

The amortization period for intangible assets acquired ranges from two to twelve years. The Company recorded $2.7 million and $46.3 million of goodwill in connection with its fiscal 2016 and 2015 acquisitions, respectively, reflecting the strategic fit and revenue and earnings growth potential of these businesses. The goodwill recorded in fiscal 2016 and 2015 relates primarily to the acquisition of the common stock of the acquirees, which is generally not deductible for tax purposes.

We are continuing our review of our fair value estimate of assets acquired and liabilities assumed for two entities acquired in fiscal 2016 disclosed above. This process will conclude as soon as we finalize information regarding facts and circumstances that existed as of the acquisition date. Goodwill for these two entities totaled $2.7 million. These measurement periods will not exceed one year from the respective acquisition dates.

Revenue included in the consolidated statement of operations for fiscal 2016 from these acquisitions for the period subsequent to the closing of the fiscal 2016 transactions were approximately $0.2 million. Aggregate loss from operations included in the consolidated statement of operations for fiscal 2016 from the acquisitions for the period subsequent to the closing of each transaction was approximately $0.3 million. As these acquisitions are not significant to the Company’s fiscal 2016 results, no unaudited pro forma financial information has been included in this report.

Dispositions

On May 22, 2015, the Company completed the sale of one of its Russian subsidiaries and recognized a loss of $0.4 million. On July 31, 2015, the Company completed the sale of its other subsidiary in Russia, as well as its subsidiary in Japan. For the year ended May 31, 2015, the Company recognized impairment charges of $2.1 million related to these sales. Aggregate charges associated with the exit of these three foreign operations was approximately $2.5 million and is included within selling, general and administrative expenses on the consolidated income statement for the year ended May 31, 2015. In the aggregate, the assets and liabilities of these subsidiaries represent 0.6% and 0.3% of consolidated assets and liabilities, respectively, and are included in their natural classifications on the consolidated balance sheet as of May 31, 2015.

Acquisition-Related expense

In the course of its acquisition activities, the Company incurs costs in connection with due diligence, professional fees, and other expenses. Additionally, the Company adjusts the fair value of acquisition-related contingent consideration liabilities on a quarterly basis. These amounts are recorded as acquisition-related (benefit) expense, net, on the consolidated statements of income and were as follows for fiscal 2016, 2015 and 2014:



	For the year ended May 31,
	2016			2015			2014
Due diligence, professional fees and other transaction costs	$	629		$	215		$	1,280
Adjustments to fair value of contingent consideration liabilities	$	(2,082	)	$	(5,382	)	$	(3,937	)
Acquisition-related (benefit) expense, net	$	(1,453	)	$	(5,167	)	$	(2,657	)

The Company’s contingent consideration liabilities are recorded on the balance sheet in accrued expenses and other liabilities.

Goodwill

12 Months Ended

May 31, 2016

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill

The changes in the carrying amount of goodwill by segment is shown below:



	Services			International			Products		Total
Balance at May 31, 2014	$	73,767		$	43,552		$	13,197	$	130,516
Goodwill acquired during the year	41,986			1,480			—		43,466
Adjustments to preliminary purchase price allocations	3,529			(367		)	—		3,162
Foreign currency translation	(2,003		)	(8,727		)	—		(10,730		)
Balance at May 31, 2015	$	117,279		$	35,938		$	13,197	$	166,414
Goodwill acquired (disposed) during the year	2,728			(374		)	—		2,354
Adjustments to preliminary purchase price allocations	270			—			—		270
Foreign currency translation	(594		)	776			—		182
Balance at May 31, 2016	$	119,683		$	36,340		$	13,197	$	169,220

The Company reviews goodwill for impairment on a reporting unit basis on March 1 of each year and whenever events or changes in circumstances indicate the carrying value of goodwill may not be recoverable. As of May 31, 2016, the Company did not identify any changes in circumstances that would indicate the carrying value of goodwill may not be recoverable.

The Company's cumulative goodwill impairment as of May 31, 2016, May 31, 2015 and May 31, 2014 was $9.9 million, which is within its International segment.

Intangible Assets

12 Months Ended

May 31, 2016

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

The gross carrying amount and accumulated amortization of intangible assets were as follows:



		May 31,
		2016							2015
	Useful Life (Years)	Gross Amount		Accumulated Amortization			Net Carrying Amount		Gross Amount		Accumulated Amortization			Net Carrying Amount
Customer relationships	5-12	$	81,262	$	(47,747	)	$	33,515	$	81,101	$	(41,009	)	$	40,092
Software/Technology	3-15	17,539		(11,855		)	5,684		15,738		(10,290		)	5,448
Covenants not to compete	2-5	10,791		(9,290		)	1,501		11,678		(8,605		)	3,073
Other	2-5	7,827		(5,035		)	2,792		6,910		(4,247		)	2,663
Total		$	117,419	$	(73,927	)	$	43,492	$	115,427	$	(64,151	)	$	51,276

Amortization expense for the years ended May 31, 2016, 2015 and 2014 was approximately $9.6 million, $11.1 million and $9.2 million, respectively, including amortization of software/technology for the years ended May 31, 2016, 2015 and 2014 of $1.0 million, $0.9 million and $0.9 million, respectively.

Amortization expense in each of the five years and thereafter subsequent to May 31, 2016 related to the Company’s intangible assets is expected to be as follows:



	Expected Amortization Expense

2017	$	8,618
2018	7,302
2019	6,119
2020	4,495
2021	4,238
Thereafter	12,720
Total	$	43,492

Accrued Expenses and Other Current Liabilities

12 Months Ended

May 31, 2016

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following:



	May 31,
	2016		2015
Accrued salaries, wages and related employee benefits	$	31,566	$	26,053
Contingent consideration	1,029		3,543
Accrued worker compensation and health benefits	4,834		3,630
Deferred revenues	3,332		3,841
Legal settlement accrual	6,320		—
Other accrued expenses	15,902		18,847
Total accrued expenses and other current liabilities	$	62,983	$	55,914

Long-Term Debt

12 Months Ended

May 31, 2016

Debt Disclosure [Abstract]

Long-Term Debt

Long-term debt consists of the following:



	May 31,
	2016			2015
Senior credit facility	$	68,999		$	83,062
Notes payable	10,111			24,632
Other	5,899			5,765
Total debt	85,009			113,459
Less: Current portion	(12,553		)	(17,902		)
Long-term debt, net of current portion	$	72,456		$	95,557

Senior Credit Facility

On October 31, 2014, the Company entered into a Third Amendment and Modification Agreement (the “Amendment”), of its revolving line of credit, the Third Amended and Restated Credit Agreement (“Credit Agreement”), dated December 21, 2011, with its lending group. The Amendment increased the Company’s revolving line of credit from $125.0 million to $175.0 million and provides that under certain circumstances the line of credit can be increased to $225.0 million. The Company may continue to borrow up to $30.0 million in non-U.S. Dollar currencies and use up to $10.0 million of the credit limit for the issuance of letters of credit. The Amendment also extended the original maturity date of the Credit Agreement from December 20, 2016 to October 30, 2019. At May 31, 2016, the Company had borrowings of $69.0 million and letters of credit of $4.8 million were outstanding under the Credit Agreement. The Company capitalized $0.7 million of costs associated with this debt modification.

Loans under the Credit Agreement bear interest at LIBOR plus an applicable LIBOR margin ranging from 1% to 1.75%, or a base rate less a margin of 1.25% to 0.375%, at the option of the Company, based upon the Company’s Funded Debt Leverage Ratio. Funded Debt Leverage Ratio is generally the ratio of (1) all outstanding indebtedness for borrowed money and other interest-bearing indebtedness as of the date of determination to (2) EBITDA (which is (a) net income, less (b) income (or plus loss) from discontinued operations and extraordinary items, plus (c) income tax expenses, plus (d) interest expense, plus (e) depreciation, depletion, and amortization (including non-cash loss on retirement of assets), plus (f) stock compensation expense, less (g) cash expense related to stock compensation, plus or minus certain other adjustments) for the period of four consecutive fiscal quarters immediately preceding the date of determination. The Company has the benefit of the lowest margin if its Funded Debt Leverage Ratio is equal to or less than 0.5 to 1, and the margin increases as the ratio increases, to the maximum margin if the ratio is greater than 2.0 to 1. The Company will also bear additional costs for market disruption, regulatory changes effecting the lenders’ funding costs, and default pricing of an additional 2% interest rate margin on any amounts not paid when due. Amounts borrowed under the Credit Agreement are secured by liens on substantially all of the assets of the Company.

The Credit Agreement contains financial covenants requiring that the Company maintain a Funded Debt Leverage Ratio of no greater than 3.25 to 1 and an Interest Coverage Ratio of at least 3.0 to 1. Interest Coverage Ratio means the ratio, as of any date of determination, of (a) EBITDA for the 12 month period immediately preceding the date of determination, to (b) all interest, premium payments, debt discount, fees, charges and related expenses of the Company and its subsidiaries in connection with borrowed money (including capitalized interest) or in connection with the deferred purchase price of assets, in each case to the extent treated as interest in accordance with GAAP, paid during the 12 month period immediately preceding the date of determination. The Credit Agreement also limits the Company’s ability to, among other things, create liens, make investments, incur more indebtedness, merge or consolidate, make dispositions of property, pay dividends and make distributions to stockholders, enter into a new line of business, enter into transactions with affiliates and enter into burdensome agreements. The Credit Agreement does not limit the Company’s ability to acquire other businesses or companies except that the acquired business or company must be in the Company's line of business, the Company must be in compliance with the financial covenants on a pro forma basis after taking into account the acquisition, and, if the acquired business is a separate subsidiary, in certain circumstances the lenders will receive the benefit of a guaranty of the subsidiary and liens on its assets and a pledge of its stock.

As of May 31, 2016, the Company was in compliance with the terms of the Credit Agreement, and has undertaken to continuously monitor compliance with these covenants.

Notes Payable and Other Debt

In connection with certain of its acquisitions, the Company issued subordinated notes payable to the sellers. The maturity of the notes that remain outstanding range from two to five years from the date of acquisition with stated interest rates ranging from 0% to 4%. The Company has discounted these obligations to reflect a 2% to 4% market interest. Unamortized discount on the notes was de minimis as of May 31, 2016 and 2015. Amortization is recorded as interest expense in the consolidated statements of income.

The Company has evaluated current market conditions and borrower credit quality and has determined that the carrying value of its long-term debt approximates fair value. The fair value of the Company’s notes payable and capital lease obligations approximates their carrying amounts based on anticipated interest rates which management believes would currently be available to the Company for similar issues of debt.

Scheduled principal payments due under all borrowing agreements in each of the five years and thereafter subsequent to May 31, 2016 are as follows:



2017	$	12,553
2018	881
2019	751
2020	69,446
2021	294
Thereafter	1,084
Total	$	85,009

Fair Value Measurements

12 Months Ended

May 31, 2016

Fair Value Disclosures [Abstract]

Fair Value Measurements

The Company performs fair value measurements in accordance with the guidance provided by ASC 820, Fair Value Measurements and Disclosures. ASC 820 defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. It also establishes a three level hierarchy that prioritizes the inputs used to measure fair value. The three levels of the hierarchy are defined as follows:

Level 1 — Inputs are unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

Level 2 — Observable inputs other than quoted prices included in Level 1, including quoted prices for similar assets or liabilities in active markets, quoted prices for identical assets or liabilities in inactive markets, inputs other than quoted prices that are observable for the asset or liability and inputs derived principally from or corroborated by observable market data.

Level 3 — Unobservable inputs reflecting the Company’s own assumptions about inputs that market participants would use in pricing the asset or liability based on the best information available.

In accordance with the fair value hierarchy described above, the following table shows the fair value of the Company’s financial liabilities that are required to be remeasured at fair value on a recurring basis:



	May 31, 2016
	Level 1		Level 2		Level 3		Total
Liabilities:
Contingent consideration	$	—	$	—	$	2,075	$	2,075
Total Liabilities	$	—	$	—	$	2,075	$	2,075



	May 31, 2015
	Level 1		Level 2		Level 3		Total
Liabilities:
Contingent consideration	$	—	$	—	$	6,411	$	6,411
Total Liabilities	$	—	$	—	$	6,411	$	6,411

The fair value of contingent consideration liabilities that was classified as Level 3 in the table above was estimated using a discounted cash flow technique with significant inputs that are not observable in the market and thus represents a Level 3 fair value measurement as defined in ASC 820. The significant inputs in the Level 3 measurement not supported by market activity include the probability assessments of expected future cash flows related to the acquisitions, appropriately discounted considering the uncertainties associated with the obligation, and as calculated in accordance with the terms of the acquisition agreements.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Share-Based Compensation

12 Months Ended

May 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Share-Based Compensation

The Company has share-based incentive awards outstanding to its eligible employees and Directors under two employee stock ownership plans: (i) the 2007 Stock Option Plan (the 2007 Plan), and (ii) the 2009 Long-Term Incentive Plan (the 2009 Plan). No further awards may be granted under the 2007 Plan, although awards granted under the 2007 Plan remain outstanding in accordance with their terms. Awards granted under the 2009 Plan may be in the form of stock options, restricted stock units and other forms of share-based incentives, including performance restricted stock units, stock appreciation rights and deferred stock rights. The 2009 Plan allows for the grant of awards of up to approximately 2,286,000 shares of common stock, of which approximately 658,000 shares were available for future grants as of May 31, 2016. As of May 31, 2016, there was an aggregate of approximately 2,232,000 stock options outstanding and approximately 902,000 unvested restricted stock units outstanding under the 2009 Plan and the 2007 Plan.

Stock Options

For the fiscal years ended May 31, 2016 and 2015, the Company recognized share-based compensation expense related to stock option awards of less than $0.1 million, respectively, and $0.7 million for the fiscal year ended May 31, 2014. No stock options were granted during the years ended May 31, 2016, 2015 and 2014. As of May 31, 2016, no unrecognized compensation costs remained related to stock option awards. Cash proceeds from, and the intrinsic value of stock options exercised during the years ended May 31, 2016, 2015 and 2014 were as follows:



	For the year ended May 31,
	2016		2015		2014
Cash proceeds from options exercised	$	543	$	750	$	996
Aggregate intrinsic value of options exercised	658		563		1,247

A summary of the stock option activity, weighted average exercise prices, options outstanding and exercisable as of May 31, 2016 is as follows (in thousands, except per share amounts):



	For the year ended May 31,
	2016				2015				2014
	Common Stock Options		Weighted Average Exercise Price		Common Stock Options		Weighted Average Exercise Price		Common Stock Options		Weighted Average Exercise Price
Outstanding at beginning of year:	2,287		$	13.13	2,352		$	13.09	2,464		$	12.93
Granted	—		$	—	—		$	—	—		$	—
Exercised	(55	)	$	9.87	(65	)	$	11.54	(103	)	$	9.67
Expired or forfeited	—		$	—	—		$	—	(9	)	$	10.03
Outstanding at end of year:	2,232		$	13.21	2,287		$	13.13	2,352		$	13.09



			For the year ended May 31, 2016
			Options Outstanding			Options Exercisable
Range of Exercise Prices	Total Options Outstanding		Weighted Average Remaining Life (Years)	Weighted Average Exercise Price		Number Exercisable		Weighted Average Exercise Price
$6.15-$11.54	137		2.3	$	9.09	137		$	9.09
$13.46-$22.35	2,095		3.2	$	13.48	2,095		$	13.48
	2,232					2,232

Aggregate Intrinsic Value	$	25,887				$	25,887

Restricted Stock Unit Awards

The Company recognized approximately $4.4 million of share-based compensation in fiscal 2016, $4.7 million of share-based compensation in fiscal 2015 and $4.0 million of share-based compensation expense in fiscal 2014 related to restricted stock unit awards. As of May 31, 2016, there were approximately $7.0 million of unrecognized compensation costs, net of estimated forfeitures, related to restricted stock unit awards, which are expected to be recognized over a remaining weighted average period of 2.1 years.

Approximately 264,000 restricted stock units were granted in fiscal 2016, 192,000 restricted stock units were granted in fiscal 2015 and 295,000 restricted stock units were granted in fiscal 2014. Approximately 223,000 restricted stock units vested in fiscal 2016, 232,000 restricted stock units vested in fiscal 2015 and 178,000 restricted stock units vested in fiscal 2014. The fair value of these units was $3.5 million, $5.2 million and $3.3 million, respectively. Upon vesting, restricted stock units are generally net share-settled to cover the required minimum withholding tax and the remaining amount is converted into an equivalent number of shares of common stock. Approximately 30,000 shares were forfeited in fiscal 2016, 24,000 shares were forfeited in fiscal 2015 and 44,000 shares were forfeited in fiscal 2014.

During the years ended May 31, 2016, 2015 and 2014, the Company granted approximately 28,000, 21,000 and 19,000 shares, respectively, of fully-vested common stock to its five non-employee directors, in connection with its non-employee director compensation plan. These shares had a grant date fair value of approximately $0.5 million, $0.4 million and $0.4 million, respectively, which is included in the share-based compensation expense recorded during the years ended May 31, 2016, 2015 and 2014.

Performance Restricted Stock Units

In fiscal 2014, the company granted one-year, two-year and three-year performance restricted stock units to its executive and certain other senior officers. These units have requisite service periods of three years and have no dividend rights. The actual payout of these units, before the fiscal 2016 modification as described below, was based on the Company’s performance over one, two and three-year periods (based on pre-established targets) and a market condition modifier based on total shareholder return (TSR) compared to an industry peer group. The one-year and two-year performance conditions of the fiscal 2014 awards were evaluated before modification of the awards and not achieved. The one-year and two-year market conditions of the fiscal 2014 awards were evaluated before modification of the awards and achieved. The one-year and two-year awards related to market conditions will payout at 170% and 105%, respectively, of target once the requisite service period is complete. The three-year performance and market condition awards were surrendered as part of the fiscal 2016 modification described below.

In fiscal 2015, the company granted performance restricted stock units to its executive and certain other senior officers. These units have requisite service periods of three years and have no dividend rights. The actual payout of these units, before the fiscal 2016 modification as described below, was based on the Company’s performance over the three-year period (based on pre-established targets) and a market condition modifier based on (TSR) compared to an industry peer group. The 2015 awards were surrendered as part of the fiscal 2016 modification described below.

In the first quarter of fiscal 2016, the Company modified its equity compensation program and granted 154,000 performance restricted stock units to its executive and certain other senior officers. As a condition for receiving any awards under the revised fiscal 2016 plan, the executive and senior officers surrendered and released all rights to receive any shares under the three-year 2014 awards and three-year 2015 awards with a performance or market condition. The Company has accounted for the fiscal 2016 awards as modifications in accordance with ASC 718, Compensation - Stock Compensation. These units have requisite service periods of five years and have no dividend rights. The actual payout of these units will vary based on the Company’s performance over a one-year period based on three metrics related to the Company’s fiscal 2016 performance: (1) Operating Income, (2) Adjusted EBITDAS, which is consistent with Adjusted EBITDA as disclosed in the financial statements, which is net income before interest, taxes, depreciation, amortization, non-cash stock-based compensation expense, acquisition related items, and other non-routine items as approved by the Company's Compensation Committee and (3) Revenue. There is also a discretionary portion based on individual performance. During the year ended May 31, 2016, the Company evaluated the performance metrics, and due to achievement above target, increased the estimated performance shares expected to be granted by approximately 85,000 units to a total of 239,000 units.

Compensation costs are initially measured assuming that the target performance conditions will be achieved. However, compensation costs related to the performance conditions are adjusted for subsequent changes in the expected outcome of the performance conditions. The discretionary portion of the fiscal 2016 awards are liability-classified and adjusted to fair value each reporting period. Compensation costs for the discretionary portion of the awards are recognized over the same five year requisite service period as the awards based on the Company’s fiscal 2016 performance.

Compensation costs related to the TSR conditions for the one-year and two-year 2014 awards described above were fixed at the measurement date, and not subsequently adjusted.

Compensation expense related to all performance restricted stock units described above was $1.6 million, $1.5 million and $1.2 million for the years ended May 31, 2016, 2015 and 2014. At May 31, 2016, there was $3.2 million of total unrecognized compensation costs related to approximately 328,000 nonvested performance restricted stock units. These costs are expected to be recognized over a weighted-average period of approximately 3.7 years.

For the fiscal years ended May 31, 2016, 2015 and 2014, the income tax benefit recognized on all share based compensation arrangements above was approximately $2.2 million, $2.3 million and $2.3 million, respectively.

Income Taxes

12 Months Ended

May 31, 2016

Income Tax Disclosure [Abstract]

Income Taxes

Income before provision for income taxes is as follows:



	For the year ended May 31,
	2016		2015			2014
Income (loss) before provision for income taxes from:
U.S. operations	$	27,772	$	26,893		$	25,433
Foreign operations	10,643		(1,162		)	9,670
Earnings before income taxes	$	38,415	$	25,731		$	35,103

The provision for income taxes consists of the following:



	For the year ended May 31,
	2016			2015			2014
Current
Federal	$	9,156		$	8,489		$	8,836
States and local	1,537			1,177			1,689
Foreign	3,672			1,493			2,484
Reserve for uncertain tax positions	(529		)	(48		)	59
Total current	13,836			11,111			13,068
Deferred
Federal	82			(145		)	(53		)
States and local	(51		)	(126		)	395
Foreign	(557		)	(2,416		)	(967		)
Total deferred	(526		)	(2,687		)	(625		)
Net change in valuation allowance	455			1,316			85
Net deferred	(71		)	(1,371		)	(540		)
Provision for income taxes	$	13,765		$	9,740		$	12,528

The provision for income taxes differs from the amount computed by applying the statutory federal tax rate to income tax as follows:



	For the year ended May 31,
	2016					2015					2014
Federal tax at statutory rate	$	13,445		35.0	%	$	9,006		35.0	%	$	12,286		35.0	%
State taxes, net of federal benefit	966			2.5	%	683			2.7	%	1,355			3.9	%
Foreign tax	(610		)	(1.6	)%	(517		)	(2.0	)%	(1,868		)	(5.3	)%
Contingent consideration	(425		)	(1.1	)%	(914		)	(3.6	)%	24			0.1	%
Permanent differences	245			0.6	%	196			0.8	%	531			1.5	%
Other	(311		)	(0.8	)%	(30		)	(0.1	)%	115			0.3	%
Change in valuation allowance	455			1.2	%	1,316			5.1	%	85			0.2	%
Total provision for income taxes	$	13,765		35.8	%	$	9,740		37.9	%	$	12,528		35.7	%

Deferred income tax attributes resulting from differences between financial accounting amounts and income tax basis of assets and liabilities are as follows:



	May 31,
	2016			2015
Deferred income tax assets
Allowance for doubtful accounts	$	940		$	1,036
Inventory	518			796
Intangible assets	1,641			1,254
Accrued expenses	4,668			3,455
Net operating loss carryforward	4,036			4,738
Capital lease obligations	1,167			379
Capital losses	719			—
Deferred share-based compensation	6,477			6,241
Other	440			370
Deferred income tax assets	20,606			18,269
Valuation allowance	(3,397		)	(3,238		)
Net deferred income tax assets	17,209			15,031
Deferred income tax liabilities
Property and equipment	(9,785		)	(8,214		)
Goodwill	(12,535		)	(10,728		)
Intangible assets	(5,989		)	(6,677		)
Other	(12		)	(44		)
Deferred income tax liabilities	(28,321		)	(25,663		)
Net deferred income taxes	$	(11,112	)	$	(10,632	)

As of May 31, 2016, the Company had federal net operating loss carry forwards (NOL’s) in the amount of approximately $0.3 million which may be utilized subject to limitation under Internal Revenue code section 382. The federal NOL's expire at various times from 2029 to 2033. In addition, as of May 31, 2016 the Company had state and foreign NOLs of $3.6 million and $12.1 million, respectively. The state NOLs expire at various times from 2025 to 2036. Approximately $1.7 million of the foreign NOLs expire at various times from 2021 to 2036, while the remainder of the Company's foreign NOLs do not expire.

In assessing the ability to realize deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will be realized. Valuation allowances are provided when management believes the Company's deferred tax assets are not recoverable based on an assessment of estimated future taxable income that incorporates ongoing, prudent and feasible tax planning strategies. At May 31, 2016, the Company has a valuation allowance of approximately $3.4 million primarily against certain state and foreign NOLs and the capital losses generated by the disposals of certain foreign subsidiaries. For the year ended May 31, 2016, the valuation allowance increased $0.2 million attributable to tax losses generated by foreign subsidiaries. Except for those deferred tax assets subject to the valuation allowance, management believes that it will realize all deferred tax assets as a result of sufficient future taxable income in each tax jurisdiction in which we have deferred tax assets.

The following table summarizes the changes in the Company’s gross unrecognized tax benefits, excluding interest and penalties:



	For the year ended May 31,
	2016			2015
Balance at June 1	$	763		$	1,016
Additions for tax positions related to the current fiscal year	29			30
Additions for tax positions related to prior years	52			—
Decreases for tax positions related to prior years	(23		)	(1		)
Impact of foreign exchange fluctuation	(91		)	(112		)
Settlements	(29		)	(50		)
Reductions related to the expiration of statutes of limitations	(398		)	(120		)
Balance at May 31	$	303		$	763

The Company has recorded the unrecognized tax benefits in other long-term liabilities in the consolidated balance sheets. As of May 31, 2016 and 2015, there were approximately $0.4 million and $1.1 million of unrecognized tax benefits, respectively, including penalties and interest that if recognized would favorably affect the effective tax rate. Interest and penalties related to unrecognized tax benefits are recorded in income tax expense and are not significant for the years ending May 31, 2016 and 2015. The Company anticipates a decrease to its unrecognized tax benefits of approximately $0.2 million excluding interest and penalties within the next 12 months.

The Company is subject to taxation in the United States and various states and foreign jurisdictions. The Company is no longer subject to U.S. federal income tax examinations for years ending before May 31, 2013 and generally is no longer subject to state, local or foreign income tax examinations by tax authorities for years ending before May 31, 2012.

The Company has not recognized U.S. tax expense on its undistributed international earnings or losses of its foreign subsidiaries since it intends to indefinitely reinvest the earnings outside the United States. Net income (loss) of foreign subsidiaries was $7.5 million and $(0.8) million for fiscal 2016 and 2015, respectively. We have recognized no deferred tax liability for the remittance of such earnings to the U.S. since it is our intention to utilize those earnings in the foreign operations. Determination of the amount of any unrecognized deferred income tax liability on this temporary difference is not practicable because of the complexities of the hypothetical calculation.

Employee Benefit Plans	12 Months Ended
Employee Benefit Plans	May 31, 2016
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plans	Employee Benefit Plans The Company provides a 401(k) savings plan for eligible U.S. based employees. Employee contributions are discretionary up to the IRS limits each year and catch up contributions are allowed for employees 50 years of age or older. Under the 401(k) plan, employees become eligible to participate on the first day of the month after six months of continuous service. Under this plan, the Company matches 50% of the employee’s contributions up to 6% of the employee’s annual compensation, as defined by the plan. There is a five-year vesting schedule for the Company match. The Company’s contribution to the plan was $3.3 million, $2.8 million and $2.5 million for the years ended May 31, 2016, 2015 and 2014, respectively. The Company participates with other employers in contributing to a union plan, which covers certain U.S. based union employees. The plan is not administered by the Company and contributions are determined in accordance with provisions of a collective bargaining agreement. The Company’s contributions to the plan were $0.2 million, $0.2 million and $0.1 million for the years ended May 31, 2016, 2015 and 2014. The Company has benefit plans covering certain employees in selected foreign countries. Amounts charged to expense under these plans were not significant in any year.

Related Party Transactions	12 Months Ended
Related Party Transactions	May 31, 2016
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions The Company leases its headquarters under an operating lease from a shareholder and officer of the Company. On August 1, 2014, the Company extended its lease at its headquarters requiring monthly payments through October 2024. Total rent payments made during fiscal 2016 were approximately $0.9 million. See Note 18 — Commitments and Contingencies for further detail related to operating leases. The Company has a lease for office space located in France, which is partly owned by a shareholder and officer. Total rent payments made during fiscal 2016 were approximately $0.2 million. The Company has a lease for office space located in Brazil, which is partly owned by a shareholder and officer. Total rent payments made during fiscal 2016 were approximately $0.1 million.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References + Details

Obligations under Capital Leases

12 Months Ended

May 31, 2016

Leases [Abstract]

Obligations under Capital Leases

The Company leases certain office space, and service equipment under capital leases, requiring monthly payments ranging from less than $1 thousand to $81 thousand, including effective interest rates that range from approximately 1% to 7% expiring through May 2022. The net book value of assets under capital lease obligations was $19.8 million and $19.9 million at May 31, 2016 and 2015, respectively.

Scheduled future minimum lease payments subsequent to May 31, 2016 are as follows:



2017	$	9,112
2018	6,491
2019	3,810
2020	1,520
2021	134
Thereafter	122
Total minimum lease payments	21,189
Less: amount representing interest	(1,422		)
Present value of minimum lease payments	19,767
Less: current portion of obligations under capital leases	(7,835		)
Obligations under capital leases, net of current portion	$	11,932

Commitments and Contingencies

12 Months Ended

May 31, 2016

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Operating Leases

The Company is party to various noncancelable lease agreements, primarily for its international and domestic office and lab space. Future minimum lease payments under noncancelable operating leases in each of the five years and thereafter subsequent to May 31, 2016 are as follows:



2017	$	9,956
2018	7,903
2019	6,580
2020	5,219
2021	4,112
Thereafter	13,039
Total	$	46,809

Total rent expense was $11.2 million, $10.6 million and $9.5 million for the years ended May 31, 2016, 2015 and 2014, respectively.

Legal Proceedings and Government Investigations

The Company is subject to periodic legal proceedings, investigations and claims that arise in the ordinary course of business. The Company cannot predict with certainty the ultimate resolution of legal proceedings, investigations and claims asserted against it. Except for the matters described below, the Company does not believe that any currently pending legal proceeding to which the Company is a party will have a material adverse effect on its business, results of operations, cash flows or financial condition. The costs of defense and amounts that may be recovered against the Company may be covered by insurance for certain matters.

Litigation and Commercial Claims

The Company is currently a defendant in a consolidated purported class and collective action, Edgar Viceral and David Kruger v Mistras Group, et al, pending in the U.S. District Court for the Northern District of California. This matter results from the consolidation of two cases originally filed in California state court in April 2015. The consolidated case alleges violations of California statutes, primarily the California Labor Code, and seeks to proceed as a collective action under the U.S. Fair Labor Standards Act. The case is predicated on claims for allegedly missed rest and meal periods, inaccurate wage statements, and failure to pay all wages due, as well as related unfair business practices, and is requesting payment of all damages, including unpaid wages, and various fines and penalties available under California and Federal law.

The parties have reached a settlement of the case, whereby the Company agreed to pay $6 million to resolve the allegations and avoid further distraction that would result if the litigation continued. The settlement is subject to court approval, and a hearing for preliminary approval is currently scheduled for August 18, 2016. The Company recorded a pre-tax charge of $6.3 million in the fourth quarter of fiscal 2016 for the settlement and payment of payroll taxes and other costs related to the settlement. The settlement will cover claims dating back to April 2011 in some cases and involves approximately 4,900 current and former employees.

During fiscal 2013, the Company performed radiography work on the construction of a pipeline project in the U.S. The owner of the pipeline project contends that certain of the radiography images the Company’s technicians prepared regarding the project did not meet the code quality interpretation standards required by the American Petroleum Institute. The project owner is claiming damages as a result of the alleged quality defects of the Company’s radiography images. No lawsuit has been filed at this time, but the Company received a demand for damages of approximately $6 million. The Company is currently unable to determine the likely outcome or reasonably estimate the amount or range of potential liability related to this matter, and accordingly, has not established any reserves for this matter.

The Company’s subsidiary in France has been involved in a dispute with a former owner of a business in France purchased by the Company’s French subsidiary. The former owner received a judgment in his favor in the amount of approximately $0.4 million for payment of the contingent consideration portion of the purchase price for the business. The judgment is being appealed, but the Company recorded a reserve for the full amount of the judgment in the fourth quarter of fiscal 2016.

Government Investigations

In May 2015, the Company received a notice from the U.S. Environmental Protection Agency (“EPA”) that it performed a preliminary assessment at a leased facility the Company operates in Cudahy, California. Based upon the preliminary assessment, the EPA is conducting an investigation of the site, which includes taking groundwater and soil samples. The purpose of the investigation is to determine whether any hazardous materials were released from the facility. The Company has been informed that certain hazardous materials and pollutants have been found in the ground water in the general vicinity of the site and the EPA is attempting to ascertain the origination or source of these materials and pollutants. Given the historic industrial use of the site, the EPA determined that the site of the Cudahy facility should be examined, along with numerous other sites in the vicinity. At this time, the Company is unable to determine whether it has any liability in connection with this matter and if so, the amount or range of any such liability, and accordingly, has not established any reserves for this matter.

In January 2012, the Company received notice of a governmental investigation concerning an environmental incident which occurred in February 2011 outside on the premises of the Cudahy facility. No human injury or property damage was reported or appears to have been caused as a result of this incident. While management cannot predict the ultimate outcome of this matter, based on its internal investigation to date, the Company does not believe the outcome will have a material effect on its financial condition or results of operations. To the Company’s knowledge, this matter has been dormant since fiscal 2012.

Acquisition-related contingencies

The Company is liable for contingent consideration in connection with certain of its acquisitions. As of May 31, 2016, total potential acquisition-related contingent consideration ranged from zero to $16.6 million and would be payable upon the achievement of specific performance metrics by certain of the acquired companies over the next four years of operations. See Note 7 - Acquisitions for further discussion of the Company’s acquisitions.

Segment Disclosure

12 Months Ended

May 31, 2016

Segment Reporting [Abstract]

Segment Disclosure

The Company’s three operating segments are:

•

Services. This segment provides asset protection solutions predominantly in North America with the largest concentration in the United States along with a growing Canadian services business, consisting primarily of non-destructive testing, and inspection and engineering services that are used to evaluate the structural integrity and reliability of critical energy, industrial and public infrastructure.


•	International. This segment offers services, products and systems similar to those of the Company’s other segments to global markets, in Europe, the Middle East, Africa, Asia and South America, but not to customers in China and South Korea, which are served by the Products and Systems segment.


•	Products and Systems. This segment designs, manufactures, sells, installs and services the Company’s asset protection products and systems, including equipment and instrumentation, predominantly in the United States.

Costs incurred for general corporate services, including finance, legal, and certain other costs that are provided to the segments are reported within Corporate and eliminations. Sales to the International segment from the Products and Systems segment and subsequent sales by the International segment of the same items are recorded and reflected in the operating performance of both segments. Additionally, engineering charges and royalty fees charged to the Services and International segments by the Products and Systems segment are reflected in the operating performance of each segment. All such intersegment transactions are eliminated in the Company’s consolidated financial reporting.

The accounting policies of the reportable segments are the same as those described in Note 2 — Summary of Significant Accounting Policies. Segment income from operations is one of the primary performance measures used by the Chief Executive Officer, who is the chief operating decision maker, to assess the performance of each segment and make decisions as to resource allocations. Certain general and administrative costs such as human resources, information technology and training are allocated to the segments. Segment income from operations excludes interest and other financial charges and income taxes. Corporate and other assets are comprised principally of cash, deposits, property, plant and equipment, domestic deferred taxes, deferred charges and other assets. Corporate loss from operations consists of administrative charges related to corporate personnel and other charges that cannot be readily identified for allocation to a particular segment.

Selected financial information by segment for the periods shown was as follows (intercompany transactions are eliminated in Corporate and eliminations):



	For the year ended May 31,
	2016			2015			2014
Revenues
Services	$	553,279		$	540,224		$	443,229
International	143,025			146,953			161,395
Products and Systems	30,293			31,255			33,544
Corporate and eliminations	(7,416		)	(7,180		)	(14,721		)
	$	719,181		$	711,252		$	623,447



	For the year ended May 31,
	2016		2015		2014
Gross profit
Services	$	145,262	$	135,201	$	114,182
International	43,613		34,572		44,893
Products and Systems	14,022		14,314		14,495
Corporate and eliminations	111		646		(627		)
	$	203,008	$	184,733	$	172,943



	For the year ended May 31,
	2016			2015			2014
Income from operations
Services	$	52,552		$	49,142		$	43,221
International	9,293			(575		)	10,238
Products and Systems	2,688			2,461			2,552
Corporate and eliminations	(21,356		)	(20,675		)	(17,716		)
	$	43,177		$	30,353		$	38,295



	For the year ended May 31,
	2016			2015		2014
Depreciation and amortization
Services	$	22,725		$	22,268	$	17,794
International	7,774			8,451		8,065
Products and Systems	2,323			2,426		2,373
Corporate and eliminations	(348		)	141		197
	$	32,474		$	33,286	$	28,429



	May 31,
	2016		2015
Intangible assets, net
Services	$	19,022	$	24,598
International	17,703		19,482
Products and Systems	6,054		7,004
Corporate and eliminations	713		192
	$	43,492	$	51,276



	May 31,
	2016		2015
Total assets
Services	$	308,008	$	301,031
International	132,643		126,643
Products and Systems	31,596		35,464
Corporate and eliminations	10,428		8,589
	$	482,675	$	471,727

Revenue and long-lived assets by geographic area was as follows:



	For the year ended May 31,
	2016		2015		2014
Revenue
United States	$	519,361	$	491,818	$	403,001
Other Americas	67,809		68,628		55,120
Europe	118,566		137,071		143,931
Asia-Pacific	13,445		13,735		21,395
	$	719,181	$	711,252	$	623,447



	May 31,
	2016		2015
Long-lived assets
United States	$	186,543	$	190,997
Other Americas	29,743		31,558
Europe	75,102		73,744
Asia-Pacific	—		647
	$	291,388	$	296,946

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

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-Name Accounting Standards Codification
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+ Details

Selected Quarterly Financial Information (unaudited)

12 Months Ended

May 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Financial Information (unaudited)

The following is a summary of the quarterly results of operations for the years ended May 31, 2016 and 2015:



Fiscal quarter ended	May 31, 2016		February 29, 2016		November 30, 2015		August 31, 2015		May 31, 2015		February 28, 2015		November 30, 2014		August 31, 2014
Revenues	$	184,187	$	160,355	$	194,786	$	179,853	$	174,686	$	163,100	$	206,893	$	166,573
Gross Profit	52,000		42,809		56,925		51,274		44,966		38,734		59,039		41,994
Income from operations	4,918		5,758		19,569		12,932		4,627		3,870		18,192		3,664
Net income attributable to Mistras Group, Inc.	$	2,764	$	3,593	$	11,425	$	6,872	$	2,171	$	1,817	$	10,427	$	1,666
Earnings per common share:
Basic	$	0.10	$	0.12	$	0.40	$	0.24	$	0.08	$	0.06	$	0.36	$	0.06
Diluted	$	0.09	$	0.12	$	0.39	$	0.23	$	0.07	$	0.06	$	0.35	$	0.06

Subsequent Events	12 Months Ended
Subsequent Events	May 31, 2016
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Subsequent to May 31, 2016, the Company completed two acquisitions of asset protection businesses for $1.2 million in cash upon closing and $0.3 million of deferred purchase price. In addition to the cash consideration, the acquisitions provide for possible contingent consideration up to $0.6 million to be earned based upon the achievement of specific performance metrics over the next three years of operation. The Company is in the process of completing the preliminary purchase price allocations. These acquisitions were not significant and no pro forma information has been included.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	May 31, 2016
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The accompanying audited consolidated financial statements include the accounts of Mistras Group, Inc. and its wholly and majority-owned subsidiaries. For subsidiaries in which the Company’s ownership interest is less than 100%, the noncontrolling interests are reported in stockholders’ equity in the accompanying consolidated balance sheets. The noncontrolling interests in net income, net of tax, is classified separately in the accompanying consolidated statements of income. All significant intercompany accounts and transactions have been eliminated in consolidation. Mistras Group, Inc.’s and its subsidiaries’ fiscal years end on May 31 except for the subsidiaries in the International segment, which end on April 30. Accordingly, the Company’s International segment subsidiaries are consolidated on a one-month lag. Therefore, in the quarter and year of acquisition, results of acquired subsidiaries in the International segment are generally included in consolidated results for one less month than the actual number of months from the acquisition date to the end of the reporting period. Management does not believe that any events occurred during the one-month lag period that would have a material effect on the Company’s consolidated financial statements for fiscal 2016. As discussed in Note 7 - Acquisitions and Dispositions, during the lag period in fiscal 2015, the Company sold an international subsidiary, and decided to sell two additional international subsidiaries. Management does not believe that any additional events occurred during the fiscal 2015 one-month lag period that would have a material effect on the Company’s consolidated financial statements. Reference to a fiscal year means the fiscal year ended May 31.
Reclassifications	Reclassifications Certain amounts in prior periods have been reclassified to conform to the current year presentation. Such reclassifications did not have a material effect on the Company's financial condition or results of operations as previously reported.
Revenue Recognition	Revenue Recognition Revenue is generally recognized when persuasive evidence of an arrangement exists, services have been rendered or products have been delivered, the fee is fixed or determinable, and collectability is reasonably assured. Shipping and handling costs are included in cost of revenues. Taxes collected from customers and remitted to governmental authorities are presented in the consolidated statements of income on a net basis. One customer accounted for 10% of our revenues in fiscal 2016, which primarily were generated from the Services segment. No customer accounted for 10% or more of our revenues in fiscal 2015 and 2014. The following revenue recognition policies define the manner in which we account for specific transaction types: Services Revenue is primarily derived from providing services on a time and material basis. Service arrangements generally consist of inspection professionals working under contract for a fixed period of time or on a specific customer project. Revenue is generally recognized when the service is performed in accordance with terms of each customer arrangement, upon completion of the earnings process and when collection is reasonably assured. At the end of any reporting period, revenue is accrued for services that have been earned which have not yet been billed. Reimbursable costs, including those related to travel and out-of-pocket expenses, are included in revenue, and equivalent amounts of reimbursable costs are included in cost of services. Products and Systems Sales of products and systems are recorded when the sales price is fixed and determinable and the risks and rewards of ownership are transferred (generally upon shipment) and when collectability is reasonably assured. These arrangements occasionally contain multiple elements or deliverables, such as hardware, software (that is essential to the functionality of the hardware) and related services. The Company recognizes revenue for delivered elements as separate units of accounting, when the delivered elements have standalone value, uncertainties regarding customer acceptance are resolved and there are no refund or return rights for the delivered elements. The Company establishes the selling prices for each deliverable based on its, vendor-specific objective evidence (“VSOE”), if available, third-party evidence, if VSOE is not available, or estimated selling price (“ESP”) if neither VSOE nor third-party evidence is available. The Company establishes VSOE of selling price using the price charged for a deliverable when sold separately and, in rare instances, using the price established by management having the relevant authority. Third-party evidence of selling price is established by evaluating largely similar and interchangeable competitor products or services in standalone sales to similarly situated customers. The Company determines ESP, by considering Internal factors such as margin objectives, pricing practices and controls, customer segment pricing strategies and the product life cycle. Consideration is also given to market conditions such as competitor pricing strategies and Industry technology life cycles. When determining ESP, the Company applies management judgment to establish margin objectives and pricing strategies and to evaluate market conditions and product life cycles. Changes in the aforementioned factors may result in a different allocation of revenue to the deliverables in multiple element arrangements and therefore may change the pattern and timing of revenue recognition for these elements, but will not change the total revenue recognized for the arrangement. A portion of the Company’s revenue is generated from engineering and manufacturing of custom products under long-term contracts that may last from several months to several years, depending on the contract. Revenues from long-term contracts are recognized on the percentage-of-completion method of accounting. Under the percentage-of-completion method of accounting revenues are recognized as work is performed. The percentage of completion at any point in time is generally based on total costs or total labor dollars incurred to date in relation to the total estimated costs or total labor dollars estimated at completion. The percentage of completion is then applied to the total contract revenue to determine the amount of revenue to be recognized in the period. Application of the percentage-of-completion method of accounting requires the use of estimates of costs to be incurred for the performance of the contract. Contract costs include all direct materials, direct labor costs and those indirect costs related to contract performance, such as indirect labor, supplies, tools, repairs, and all costs associated with operation of equipment. The cost estimation process is based upon the professional knowledge and experience of our engineers, project managers and financial professionals. Factors that are considered in estimating the work to be completed include the availability and productivity of labor, the nature and complexity of the work to be performed, the effect of change orders, the availability of materials, the effect of any delays in our project performance and the recoverability of any claims. Whenever revisions of estimated contract costs and contract values indicate that the contract costs will exceed estimated revenues, thus creating a loss, a provision for the total estimated loss is recorded in that period.
Use of Estimates	Use of Estimates The preparation of financial statements in accordance with generally accepted accounting principles requires that the Company make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses and disclosure of contingent assets and liabilities at the date of financial statements. The accounting policies that the Company believes require more significant estimates and assumptions include: revenue recognition, valuations of accounts receivable, long lived assets, goodwill, and deferred tax assets and uncertain tax positions. The Company bases its estimates and assumptions on historical experience, known or expected trends and various other assumptions that it believes to be reasonable. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates, which may cause the Company’s future results to be significantly affected.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents.
Accounts Receivable	Accounts Receivable Accounts receivable are stated net of an allowance for doubtful accounts and sales allowances. Outstanding accounts receivable balances are reviewed periodically, and allowances are provided at such time that management believes it is probable that such balances will not be collected within a reasonable period of time. The Company extends credit to its customers based upon credit evaluations in the normal course of business, primarily with 30-day terms. Bad debts are provided for based on historical experience and management’s evaluation of outstanding accounts receivable. Accounts are generally written off when they are deemed uncollectible.
Inventories	Inventories Inventories are stated at the lower of cost, as determined by using the first-in, first-out method, or market. Work in process and finished goods inventory include material, direct labor, variable costs and overhead.
Purchased and Internal-Use Software	Purchased and Internal-Use Software The Company capitalizes certain costs that are incurred to purchase or to create and implement internal-use software, which includes software coding, installation and testing. Capitalized costs are amortized on a straight-line basis over three years, the estimated useful life of the software.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are recorded at cost. Depreciation of property, plant and equipment is computed utilizing the straight-line method over the estimated useful lives of the assets. Amortization of leasehold improvements is computed utilizing the straight-line method over the shorter of the remaining lease term or estimated useful life. Repairs and maintenance costs are expensed as incurred.
Goodwill	Goodwill Goodwill represents the excess purchase price of acquired businesses over the fair values attributed to underlying net tangible assets and identifiable intangible assets. The Company tests the carrying value of goodwill for impairment at a “reporting unit” level (which for the Company is represented by (i) our Services segment, (ii) our Products and Systems segment, and (iii) the European component and (iv) Brazilian component of our International segment), using a qualitative assessment for its Services reporting unit and a two-step approach for its remaining reporting units, annually as of March 1, or whenever an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. If the fair value of a reporting unit is less than its carrying value, this is an indicator that the goodwill assigned to that reporting unit may be impaired. In this case, a second step is performed to allocate the fair value of the reporting unit to the assets and liabilities of the reporting unit as if it had just been acquired in a business combination, and as if the purchase price was equivalent to the fair value of the reporting unit. The excess of the fair value of the reporting unit over the amounts assigned to its assets and liabilities is referred to as the implied fair value of goodwill. The implied fair value of the reporting unit’s goodwill is then compared to the actual carrying value of goodwill. If the implied fair value is less than the carrying value, an impairment loss would be recorded to reduce the carrying value of goodwill to its implied fair value. The Company considers the income and market approaches to estimating the fair value of our reporting units, which requires significant judgment in evaluation of economic and industry trends, estimated future cash flows, discount rates and other factors. The Company believes that the fair values of each of its reporting units are substantially in excess of their respective carrying amounts. Significant deterioration in industry or economic trends, disruptions to our business, inability to effectively integrate acquired businesses, or other factors, may cause these fair value to decline, possibly resulting in impairment charges to goodwill in future periods.
Impairment of Long-lived Assets	Impairment of Long-lived Assets The Company reviews the recoverability of its long-lived assets on a periodic basis in order to identify indicators of a possible impairment. The assessment for potential impairment is based primarily on the Company’s ability to recover the carrying value of its long-lived assets from expected future undiscounted cash flows. If the total expected future undiscounted cash flows are less than the carrying amount of the assets, a loss is recognized for the difference between fair value (computed based upon the expected future discounted cash flows) and the carrying value of the assets.
Research and Engineering	Research and Engineering Research and product development costs are expensed as incurred.
Advertising, Promotions and Marketing	Advertising, Promotions and Marketing The costs for advertising, promotion and marketing programs are expensed as incurred and are included in selling, general and administrative expenses.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of cash and cash equivalents, accounts receivable, accounts payable and other financial current assets and liabilities approximate fair value based on the short-term nature of the items. The carrying value of long-term debt approximates fair value due to the variable-rate structure of the debt. The fair value of the Company’s notes payable and capital lease obligations approximate their carrying amounts as those obligations bear interest at rates which management believes would currently be available to the Company for similar obligations.
Foreign Currency Translation	Foreign Currency Translation The financial position and results of operations of the Company’s foreign subsidiaries are measured using their functional currencies, which, is their local currency. Assets and liabilities of foreign subsidiaries are translated into the U.S. Dollar at the exchange rates in effect at the balance sheet date. Income and expenses are translated at the average exchange rate during the period. Translation gains and losses are reported as a component of other comprehensive income (loss) for the period and included in accumulated other comprehensive income (loss) within stockholders’ equity.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents and accounts receivable. At times, cash deposits may exceed the limits insured by the Federal Deposit Insurance Corporation. The Company believes it is not exposed to any significant credit risk or risk of nonperformance of financial institutions.
Self-Insurance	Self-Insurance The Company is self-insured for certain losses relating to workers’ compensation and health benefits claims. The Company maintains third-party excess insurance coverage for all workers compensation and health benefit claims in excess of approximately $0.3 million to reduce its exposure from such claims. Self-insured losses are accrued when it is probable that an uninsured claim has been incurred but not reported and the amount of the loss can be reasonably estimated at the balance sheet date.
Share-based Compensation	Share-based Compensation The value of services received from employees and directors in exchange for an award of an equity instrument is measured based on the grant-date fair value of the award. The computed value is recognized as a non-cash cost on a straight-line basis over the period the individual provides services, which is typically the vesting period of the award with the exception of awards containing an internal performance measure which is recognized on a straight-line basis over the vesting period subject to the probability of meeting the performance requirements and adjusted for the number of shares expected to be earned. As share-based compensation expense is based on awards ultimately expected to vest, the amount of expense has been reduced for estimated forfeitures. The cost of these awards is recorded in selling, general and administrative expense in the company’s consolidated statements of income.
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Deferred income tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and tax credit carry-forwards. Deferred income tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred income tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A valuation allowance is provided if it is more likely than not that some or all of a deferred income tax asset will not be realized. Financial accounting standards prescribe a minimum recognition threshold a tax position is required to meet before being recognized in the financial statements. These standards also provide guidance on de-recognition, measurement, and classification of amounts relating to uncertain tax positions, accounting for and disclosure of interest and penalties, accounting in interim periods and disclosures required. Interest and penalties related to unrecognized tax positions are recognized as incurred within “provision for income taxes” in the consolidated statements of income.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU No. 2014-09, Revenue from Contracts with Customers, which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The ASU will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. The new standard is effective for fiscal years and interim periods within those fiscal years beginning December 15, 2017, as a result of a one year deferral in the standard issued by the FASB in August 2015 with ASU 2015-14, Revenue from Contracts with Customers - Deferral of the Effective Date. Early application is not permitted. The standard permits the use of either the retrospective or cumulative effect transition method. The Company is evaluating the effect that ASU 2014-09 will have on its consolidated financial statements and related disclosures. In September 2015, the FASB issued ASU No. 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments. This amendment will simplify the accounting for adjustments made to provisional amounts recognized in a business combination and eliminates the requirement to retrospectively account for those adjustments in previous reporting periods. This update will require on the face of the income statement or in the notes to the financial statements the amount recorded in current-period earnings that would have previously been recorded if the adjustment to the provisional amounts had been recognized as of the acquisition date. ASU 2015-16 is effective for fiscal years, and interim periods within those fiscal years beginning after December 15, 2015. This update should be applied prospectively and earlier adoption is permitted for financial statements that have not been issued. The Company is evaluating the effect that ASU 2015-16 will have on its consolidated financial statements and related disclosures. In November 2015, the FASB issued ASU No. 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes. This amendment will simplify the presentation of deferred tax assets and liabilities on the balance sheet and require all deferred tax assets and liabilities to be treated as non-current. ASU 2015-17 is effective for fiscal years, and interim periods within those fiscal years beginning after December 15, 2016, with early adoption permitted. The Company is evaluating the effect that ASU 2015-17 will have on its consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). This amendment supersedes previous accounting guidance (Topic 840) and requires all leases, with exception of leases with a term of 12 months or less, to be recorded on the balance sheet as lease assets and lease liabilities. ASU 2016-02 is effective for fiscal years, and interim periods within those fiscal years beginning after December 15, 2018, with early adoption permitted. The standard requires lessees and lessors to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. The Company is evaluating the effect that ASU 2016-02 will have on its consolidated financial statements and related disclosures. In March 2016, the FASB issues ASU No. 2016-09, Stock Compensation (Topic 718). This amendment will simplify certain aspects of accounting for share-based payment transactions, which include accounting for income taxes and the related impact on the statement of cash flows, an option to account for forfeitures when they occur in addition to the existing guidance to estimate the forfeitures of awards, classification of awards as either equity or liabilities and classification on the statement of cash flows for employee taxes paid to tax authorities on shares withheld for vesting. ASU 2016-09 is effective for fiscal years, and interim periods within those fiscal years beginning after December 15, 2016, with early adoption permitted. The Company is evaluating the effect that ASU 2016-09 will have on its consolidated financial statements and related disclosures.
Fair Value Measurement	Fair Value Measurements The Company performs fair value measurements in accordance with the guidance provided by ASC 820, Fair Value Measurements and Disclosures. ASC 820 defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. It also establishes a three level hierarchy that prioritizes the inputs used to measure fair value. The three levels of the hierarchy are defined as follows: Level 1 — Inputs are unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2 — Observable inputs other than quoted prices included in Level 1, including quoted prices for similar assets or liabilities in active markets, quoted prices for identical assets or liabilities in inactive markets, inputs other than quoted prices that are observable for the asset or liability and inputs derived principally from or corroborated by observable market data. Level 3 — Unobservable inputs reflecting the Company’s own assumptions about inputs that market participants would use in pricing the asset or liability based on the best information available.

Description of Business and Basis of Presentation (Tables)

12 Months Ended

May 31, 2016

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Quantifying Prior Year Misstatement Corrected in Current Year Financial Statements

In accordance with the SEC Staff Accounting Bulletin (SAB) No. 99, Materiality, and SAB No. 108, Considering the Effects of Prior Year Misstatements when Quantifying Misstatements in Current Year Financial Statements, management evaluated the materiality of the errors from qualitative and quantitative perspectives, and concluded that the errors were immaterial. Accordingly, management has corrected the presentation of the affected line items of the accompanying Consolidated Statement of Cash Flows for the year ended May 31, 2015, as summarized below. These changes did not impact the Company’s net income, balance sheet, or stockholders’ equity for any periods previously reported.



	Previously Reported		Revised
Cash flows from operating activities
Accounts payable	(6,281	)	(6,571	)
Accrued expenses and other liabilities	2,500		2,006
Net cash provided by operating activities	50,624		49,840

Cash flows from investing activities
Acquisition of businesses, net of cash acquired	(34,967	)	(34,677	)
Net cash used in investing activities	(49,941	)	(49,651	)

Cash flows from financing activities
Proceeds from borrowings of long-term debt	—		2,232
Repayments of long-term debt	(9,224	)	(11,457	)
Net borrowings against revolver	21,914		23,500
Net cash provided by financing activities	481		2,066

Effect of exchange rate changes on cash and cash equivalents	(629	)	(1,720	)

Earnings per Share (Tables)

12 Months Ended

May 31, 2016

Earnings Per Share [Abstract]

Schedule of computations of basic and diluted earnings per share

The following table sets forth the computations of basic and diluted earnings per share:



	For the year ended May 31,
	2016		2015		2014
Basic earnings per share
Numerator:
Net income attributable to Mistras Group, Inc.	$	24,654	$	16,081	$	22,518
Denominator
Weighted average common shares outstanding	28,856		28,613		28,365
Basic earnings per share	$	0.85	$	0.56	$	0.79

Diluted earnings per share:
Numerator:
Net income attributable to Mistras Group, Inc.	$	24,654	$	16,081	$	22,518
Denominator
Weighted average common shares outstanding	28,856		28,613		28,365
Dilutive effect of stock options outstanding	712		719		775
Dilutive effect of restricted stock units outstanding	323		258		184
	29,891		29,590		29,324
Diluted earnings per share	$	0.82	$	0.54	$	0.77

Schedule of potential common shares that were excluded from the computation of diluted earnings per share

The following potential common shares were excluded from the computation of diluted earnings per share, as the effect would have been anti-dilutive:



	For the year ended May 31,
	2016	2015	2014
Potential common stock attributable to stock options outstanding	5	6	5
Potential common stock attributable to performance awards outstanding	24	1	121
Total	29	7	126

Accounts Receivable, net (Tables)

12 Months Ended

May 31, 2016

Receivables [Abstract]

Schedule of accounts receivable

Accounts receivable consist of the following:



	May 31,
	2016			2015
Trade accounts receivable	$	140,820		$	136,208
Allowance for doubtful accounts	(2,907		)	(2,980		)
Accounts receivable, net	$	137,913		$	133,228

Inventories (Tables)

12 Months Ended

May 31, 2016

Inventory Disclosure [Abstract]

Schedule of inventories

Inventories consist of the following:



	May 31,
	2016		2015
Raw materials	$	3,827	$	4,194
Work in progress	1,743		1,604
Finished goods	2,839		3,178
Services-related consumable supplies	1,509		1,865
Inventory	$	9,918	$	10,841

Property, Plant and Equipment, net (Tables)

12 Months Ended

May 31, 2016

Property, Plant and Equipment [Abstract]

Schedule of Property, plant and equipment

Property, plant and equipment consist of the following:



	May 31,
	Useful Life	2016			2015
	(Years)
Land		$	1,735		$	1,856
Building and improvements	30-40	19,364			17,712
Office furniture and equipment	5-8	8,692			7,934
Machinery and equipment	5-7	173,053			162,762
		202,844			190,264
Accumulated depreciation and amortization		(124,168		)	(111,008		)
Property, plant and equipment, net		$	78,676		$	79,256

Acquisitions and Dispositions (Tables)

12 Months Ended

May 31, 2016

Business Combinations [Abstract]

Summary of estimated fair value of assets acquired and liabilities assumed at the date of acquisition

The following table summarizes the estimated fair value of the assets acquired and liabilities assumed and any subsequent adjustments made during the fiscal year ended May 31, 2016:



	2016			2015
Number of entities	2			4

Cash paid	$	1,784		$	35,755
Subordinated notes issued	—			20,505
Contingent consideration	991			2,255
Consideration paid	$	2,775		$	58,515

Current net assets	$	180		$	2,770
Debt and other long-term liabilities	(546		)	(5,889		)
Property, plant and equipment	485			7,395
Deferred tax liability	(72		)	(2,467		)
Intangibles	—			10,394
Goodwill	2,728			46,312
Net assets acquired	$	2,775		$	58,515

Schedule of acquisition-related expense, net



	For the year ended May 31,
	2016			2015			2014
Due diligence, professional fees and other transaction costs	$	629		$	215		$	1,280
Adjustments to fair value of contingent consideration liabilities	$	(2,082	)	$	(5,382	)	$	(3,937	)
Acquisition-related (benefit) expense, net	$	(1,453	)	$	(5,167	)	$	(2,657	)

Goodwill (Tables)

12 Months Ended

May 31, 2016

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of changes in carrying amount of goodwill by segment

The changes in the carrying amount of goodwill by segment is shown below:



	Services			International			Products		Total
Balance at May 31, 2014	$	73,767		$	43,552		$	13,197	$	130,516
Goodwill acquired during the year	41,986			1,480			—		43,466
Adjustments to preliminary purchase price allocations	3,529			(367		)	—		3,162
Foreign currency translation	(2,003		)	(8,727		)	—		(10,730		)
Balance at May 31, 2015	$	117,279		$	35,938		$	13,197	$	166,414
Goodwill acquired (disposed) during the year	2,728			(374		)	—		2,354
Adjustments to preliminary purchase price allocations	270			—			—		270
Foreign currency translation	(594		)	776			—		182
Balance at May 31, 2016	$	119,683		$	36,340		$	13,197	$	169,220

Intangible Assets (Tables)

12 Months Ended

May 31, 2016

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of gross amount and accumulated amortization of intangible assets

The gross carrying amount and accumulated amortization of intangible assets were as follows:



		May 31,
		2016							2015
	Useful Life (Years)	Gross Amount		Accumulated Amortization			Net Carrying Amount		Gross Amount		Accumulated Amortization			Net Carrying Amount
Customer relationships	5-12	$	81,262	$	(47,747	)	$	33,515	$	81,101	$	(41,009	)	$	40,092
Software/Technology	3-15	17,539		(11,855		)	5,684		15,738		(10,290		)	5,448
Covenants not to compete	2-5	10,791		(9,290		)	1,501		11,678		(8,605		)	3,073
Other	2-5	7,827		(5,035		)	2,792		6,910		(4,247		)	2,663
Total		$	117,419	$	(73,927	)	$	43,492	$	115,427	$	(64,151	)	$	51,276

Schedule of expected amortization expense of intangible assets

Amortization expense in each of the five years and thereafter subsequent to May 31, 2016 related to the Company’s intangible assets is expected to be as follows:



	Expected Amortization Expense

2017	$	8,618
2018	7,302
2019	6,119
2020	4,495
2021	4,238
Thereafter	12,720
Total	$	43,492

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

May 31, 2016

Payables and Accruals [Abstract]

Schedule of accrued expenses and other current liabilities

Accrued expenses and other current liabilities consist of the following:



	May 31,
	2016		2015
Accrued salaries, wages and related employee benefits	$	31,566	$	26,053
Contingent consideration	1,029		3,543
Accrued worker compensation and health benefits	4,834		3,630
Deferred revenues	3,332		3,841
Legal settlement accrual	6,320		—
Other accrued expenses	15,902		18,847
Total accrued expenses and other current liabilities	$	62,983	$	55,914

Long-Term Debt (Tables)

12 Months Ended

May 31, 2016

Debt Disclosure [Abstract]

Schedule of long-term debt

Long-term debt consists of the following:



	May 31,
	2016			2015
Senior credit facility	$	68,999		$	83,062
Notes payable	10,111			24,632
Other	5,899			5,765
Total debt	85,009			113,459
Less: Current portion	(12,553		)	(17,902		)
Long-term debt, net of current portion	$	72,456		$	95,557

Schedule of principal payments due under all borrowing agreements

Scheduled principal payments due under all borrowing agreements in each of the five years and thereafter subsequent to May 31, 2016 are as follows:



2017	$	12,553
2018	881
2019	751
2020	69,446
2021	294
Thereafter	1,084
Total	$	85,009

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
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+ Details

Fair Value Measurements (Tables)

12 Months Ended

May 31, 2016

Fair Value Disclosures [Abstract]

Schedule of fair value of the Company's financial liabilities that are required to be remeasured at fair value on a recurring basis



	May 31, 2016
	Level 1		Level 2		Level 3		Total
Liabilities:
Contingent consideration	$	—	$	—	$	2,075	$	2,075
Total Liabilities	$	—	$	—	$	2,075	$	2,075



	May 31, 2015
	Level 1		Level 2		Level 3		Total
Liabilities:
Contingent consideration	$	—	$	—	$	6,411	$	6,411
Total Liabilities	$	—	$	—	$	6,411	$	6,411

Share-Based Compensation (Tables)

12 Months Ended

May 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of cash proceeds from, and the intrinsic value of, stock options exercised

Cash proceeds from, and the intrinsic value of stock options exercised during the years ended May 31, 2016, 2015 and 2014 were as follows:



	For the year ended May 31,
	2016		2015		2014
Cash proceeds from options exercised	$	543	$	750	$	996
Aggregate intrinsic value of options exercised	658		563		1,247

Summary of stock option activity, weighted average exercise prices, options outstanding and exercisable

A summary of the stock option activity, weighted average exercise prices, options outstanding and exercisable as of May 31, 2016 is as follows (in thousands, except per share amounts):



	For the year ended May 31,
	2016				2015				2014
	Common Stock Options		Weighted Average Exercise Price		Common Stock Options		Weighted Average Exercise Price		Common Stock Options		Weighted Average Exercise Price
Outstanding at beginning of year:	2,287		$	13.13	2,352		$	13.09	2,464		$	12.93
Granted	—		$	—	—		$	—	—		$	—
Exercised	(55	)	$	9.87	(65	)	$	11.54	(103	)	$	9.67
Expired or forfeited	—		$	—	—		$	—	(9	)	$	10.03
Outstanding at end of year:	2,232		$	13.21	2,287		$	13.13	2,352		$	13.09

Schedule of information concerning outstanding and exercisable options



			For the year ended May 31, 2016
			Options Outstanding			Options Exercisable
Range of Exercise Prices	Total Options Outstanding		Weighted Average Remaining Life (Years)	Weighted Average Exercise Price		Number Exercisable		Weighted Average Exercise Price
$6.15-$11.54	137		2.3	$	9.09	137		$	9.09
$13.46-$22.35	2,095		3.2	$	13.48	2,095		$	13.48
	2,232					2,232

Aggregate Intrinsic Value	$	25,887				$	25,887

Income Taxes (Tables)

12 Months Ended

May 31, 2016

Income Tax Disclosure [Abstract]

Schedule of income before provision for income taxes

Income before provision for income taxes is as follows:



	For the year ended May 31,
	2016		2015			2014
Income (loss) before provision for income taxes from:
U.S. operations	$	27,772	$	26,893		$	25,433
Foreign operations	10,643		(1,162		)	9,670
Earnings before income taxes	$	38,415	$	25,731		$	35,103

Schedule of provision for income taxes

The provision for income taxes consists of the following:



	For the year ended May 31,
	2016			2015			2014
Current
Federal	$	9,156		$	8,489		$	8,836
States and local	1,537			1,177			1,689
Foreign	3,672			1,493			2,484
Reserve for uncertain tax positions	(529		)	(48		)	59
Total current	13,836			11,111			13,068
Deferred
Federal	82			(145		)	(53		)
States and local	(51		)	(126		)	395
Foreign	(557		)	(2,416		)	(967		)
Total deferred	(526		)	(2,687		)	(625		)
Net change in valuation allowance	455			1,316			85
Net deferred	(71		)	(1,371		)	(540		)
Provision for income taxes	$	13,765		$	9,740		$	12,528

Schedule of provision for income taxes computed by applying the statutory federal tax rate

The provision for income taxes differs from the amount computed by applying the statutory federal tax rate to income tax as follows:



	For the year ended May 31,
	2016					2015					2014
Federal tax at statutory rate	$	13,445		35.0	%	$	9,006		35.0	%	$	12,286		35.0	%
State taxes, net of federal benefit	966			2.5	%	683			2.7	%	1,355			3.9	%
Foreign tax	(610		)	(1.6	)%	(517		)	(2.0	)%	(1,868		)	(5.3	)%
Contingent consideration	(425		)	(1.1	)%	(914		)	(3.6	)%	24			0.1	%
Permanent differences	245			0.6	%	196			0.8	%	531			1.5	%
Other	(311		)	(0.8	)%	(30		)	(0.1	)%	115			0.3	%
Change in valuation allowance	455			1.2	%	1,316			5.1	%	85			0.2	%
Total provision for income taxes	$	13,765		35.8	%	$	9,740		37.9	%	$	12,528		35.7	%

Schedule of deferred income tax assets and liabilities

Deferred income tax attributes resulting from differences between financial accounting amounts and income tax basis of assets and liabilities are as follows:



	May 31,
	2016			2015
Deferred income tax assets
Allowance for doubtful accounts	$	940		$	1,036
Inventory	518			796
Intangible assets	1,641			1,254
Accrued expenses	4,668			3,455
Net operating loss carryforward	4,036			4,738
Capital lease obligations	1,167			379
Capital losses	719			—
Deferred share-based compensation	6,477			6,241
Other	440			370
Deferred income tax assets	20,606			18,269
Valuation allowance	(3,397		)	(3,238		)
Net deferred income tax assets	17,209			15,031
Deferred income tax liabilities
Property and equipment	(9,785		)	(8,214		)
Goodwill	(12,535		)	(10,728		)
Intangible assets	(5,989		)	(6,677		)
Other	(12		)	(44		)
Deferred income tax liabilities	(28,321		)	(25,663		)
Net deferred income taxes	$	(11,112	)	$	(10,632	)

Summary of changes in Company's gross unrecognized tax benefits, excluding interest and penalties

The following table summarizes the changes in the Company’s gross unrecognized tax benefits, excluding interest and penalties:



	For the year ended May 31,
	2016			2015
Balance at June 1	$	763		$	1,016
Additions for tax positions related to the current fiscal year	29			30
Additions for tax positions related to prior years	52			—
Decreases for tax positions related to prior years	(23		)	(1		)
Impact of foreign exchange fluctuation	(91		)	(112		)
Settlements	(29		)	(50		)
Reductions related to the expiration of statutes of limitations	(398		)	(120		)
Balance at May 31	$	303		$	763

Obligations under Capital Leases (Tables)

12 Months Ended

May 31, 2016

Leases [Abstract]

Scheduled future minimum lease payments

Scheduled future minimum lease payments subsequent to May 31, 2016 are as follows:



2017	$	9,112
2018	6,491
2019	3,810
2020	1,520
2021	134
Thereafter	122
Total minimum lease payments	21,189
Less: amount representing interest	(1,422		)
Present value of minimum lease payments	19,767
Less: current portion of obligations under capital leases	(7,835		)
Obligations under capital leases, net of current portion	$	11,932

Commitments and Contingencies (Tables)

12 Months Ended

May 31, 2016

Commitments and Contingencies Disclosure [Abstract]

Schedule of future minimum lease payments under noncancelable operating leases

Future minimum lease payments under noncancelable operating leases in each of the five years and thereafter subsequent to May 31, 2016 are as follows:



2017	$	9,956
2018	7,903
2019	6,580
2020	5,219
2021	4,112
Thereafter	13,039
Total	$	46,809

Segment Disclosure (Tables)

12 Months Ended

May 31, 2016

Segment Reporting [Abstract]

Schedule of financial information by segment

Selected financial information by segment for the periods shown was as follows (intercompany transactions are eliminated in Corporate and eliminations):



	For the year ended May 31,
	2016			2015			2014
Revenues
Services	$	553,279		$	540,224		$	443,229
International	143,025			146,953			161,395
Products and Systems	30,293			31,255			33,544
Corporate and eliminations	(7,416		)	(7,180		)	(14,721		)
	$	719,181		$	711,252		$	623,447



	For the year ended May 31,
	2016		2015		2014
Gross profit
Services	$	145,262	$	135,201	$	114,182
International	43,613		34,572		44,893
Products and Systems	14,022		14,314		14,495
Corporate and eliminations	111		646		(627		)
	$	203,008	$	184,733	$	172,943



	For the year ended May 31,
	2016			2015			2014
Income from operations
Services	$	52,552		$	49,142		$	43,221
International	9,293			(575		)	10,238
Products and Systems	2,688			2,461			2,552
Corporate and eliminations	(21,356		)	(20,675		)	(17,716		)
	$	43,177		$	30,353		$	38,295



	For the year ended May 31,
	2016			2015		2014
Depreciation and amortization
Services	$	22,725		$	22,268	$	17,794
International	7,774			8,451		8,065
Products and Systems	2,323			2,426		2,373
Corporate and eliminations	(348		)	141		197
	$	32,474		$	33,286	$	28,429



	May 31,
	2016		2015
Intangible assets, net
Services	$	19,022	$	24,598
International	17,703		19,482
Products and Systems	6,054		7,004
Corporate and eliminations	713		192
	$	43,492	$	51,276



	May 31,
	2016		2015
Total assets
Services	$	308,008	$	301,031
International	132,643		126,643
Products and Systems	31,596		35,464
Corporate and eliminations	10,428		8,589
	$	482,675	$	471,727

Schedule of revenue and long-lived assets by geographic area

Revenue and long-lived assets by geographic area was as follows:



	For the year ended May 31,
	2016		2015		2014
Revenue
United States	$	519,361	$	491,818	$	403,001
Other Americas	67,809		68,628		55,120
Europe	118,566		137,071		143,931
Asia-Pacific	13,445		13,735		21,395
	$	719,181	$	711,252	$	623,447



	May 31,
	2016		2015
Long-lived assets
United States	$	186,543	$	190,997
Other Americas	29,743		31,558
Europe	75,102		73,744
Asia-Pacific	—		647
	$	291,388	$	296,946

Selected Quarterly Financial Information (unaudited) (Tables)

12 Months Ended

May 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Summary of the quarterly results of operations

The following is a summary of the quarterly results of operations for the years ended May 31, 2016 and 2015:



Fiscal quarter ended	May 31, 2016		February 29, 2016		November 30, 2015		August 31, 2015		May 31, 2015		February 28, 2015		November 30, 2014		August 31, 2014
Revenues	$	184,187	$	160,355	$	194,786	$	179,853	$	174,686	$	163,100	$	206,893	$	166,573
Gross Profit	52,000		42,809		56,925		51,274		44,966		38,734		59,039		41,994
Income from operations	4,918		5,758		19,569		12,932		4,627		3,870		18,192		3,664
Net income attributable to Mistras Group, Inc.	$	2,764	$	3,593	$	11,425	$	6,872	$	2,171	$	1,817	$	10,427	$	1,666
Earnings per common share:
Basic	$	0.10	$	0.12	$	0.40	$	0.24	$	0.08	$	0.06	$	0.36	$	0.06
Diluted	$	0.09	$	0.12	$	0.39	$	0.23	$	0.07	$	0.06	$	0.35	$	0.06

Description of Business and Basis of Presentation - Additional Information (Details)	12 Months Ended
	May 31, 2016 mo subsidiary
Principles of Consolidation
Difference of period between the consolidation of International segment subsidiaries	1 month
Number of months less than the actual number of months from the acquisition date for which results of international segment subsidiaries are included in consolidation \| mo	1
Disposal Of Foreign Subsidiaries \| Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations \| International
Principles of Consolidation
Number of additional subsidiaries for sale \| subsidiary	2

Description of Business and Basis of Presentation - Immaterial Correction (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accounts payable	$ 254	$ (6,571)	$ 6,125
Accrued expenses and other liabilities	10,187	2,006	4,532
Net cash provided by operating activities	68,124	49,840	36,873
Acquisition of businesses, net of cash acquired	(1,743)	(34,677)	(21,924)
Net cash used in investing activities		(49,651)
Proceeds from borrowings of long-term debt	2,737	2,232	0
Repayments of long-term debt	(17,580)	(11,457)	(8,830)
Net borrowings against revolver		23,500
Net cash provided by financing activities	(40,378)	2,066	3,262
Effect of exchange rate changes on cash and cash equivalents	$ (361)	(1,720)	$ 88
Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accounts payable		(6,281)
Accrued expenses and other liabilities		2,500
Net cash provided by operating activities		50,624
Acquisition of businesses, net of cash acquired		(34,967)
Net cash used in investing activities		(49,941)
Proceeds from borrowings of long-term debt		0
Repayments of long-term debt		(9,224)
Net borrowings against revolver		21,914
Net cash provided by financing activities		481
Effect of exchange rate changes on cash and cash equivalents		$ (629)

Summary of Significant Accounting Policies - Receivables, Concentration Risk and Self Insurance (Details) $ in Millions	12 Months Ended
	May 31, 2016 USD ($) customer	May 31, 2015 customer	May 31, 2014 customer
Self-Insurance
Minimum amount of workers compensation and health benefit claims for which third-party excess insurance coverage maintained \| $	$ 0.3
Accounts receivable, net \| Customer concentration risk
Concentration of Credit Risk
Number of customers	1	0
Percentage of concentration risk	11.00%	10.00%
Revenues \| Customer concentration risk
Concentration of Credit Risk
Number of customers	1	0	0
Percentage of concentration risk	10.00%	10.00%	10.00%

Summary of Significant Accounting Policies - Software and Advertising Costs and Derivatives (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Advertising, Promotions and Marketing
Advertising expense	$ 1.8	$ 2.2	$ 1.8
Foreign Currency Translation
Foreign currency transaction (gains) losses	$ (0.1)	$ 1.5	$ 0.1
Software/Technology
Software Costs
Estimated useful Life	3 years

Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2014	May 31, 2016	May 31, 2015	May 31, 2014
Basic earnings per share
Net income attributable to Mistras Group, Inc.	$ 2,764	$ 3,593	$ 11,425	$ 6,872	$ 2,171	$ 1,817	$ 10,427	$ 1,666	$ 24,654	$ 16,081	$ 22,518
Denominator
Weighted average common shares outstanding (in shares)									28,856	28,613	28,365
Basic earnings per share (in dollars per share)	$ 0.10	$ 0.12	$ 0.40	$ 0.24	$ 0.08	$ 0.06	$ 0.36	$ 0.06	$ 0.85	$ 0.56	$ 0.79
Denominator
Weighted average common shares outstanding (in shares)									28,856	28,613	28,365
Dilutive effect of stock options outstanding (in shares)									712	719	775
Dilutive effect of restricted stock units outstanding (in shares)									323	258	184
Weighted average common shares outstanding, diluted (in shares)									29,891	29,590	29,324
Diluted earnings per share (in dollars per share)	$ 0.09	$ 0.12	$ 0.39	$ 0.23	$ 0.07	$ 0.06	$ 0.35	$ 0.06	$ 0.82	$ 0.54	$ 0.77
Earnings per share
Total shares									29	7	126
Potential common stock attributable to stock options outstanding
Earnings per share
Total shares									5	6	5
Potential common stock attributable to performance awards outstanding
Earnings per share
Total shares									24	1	121

Accounts Receivable, net (Details) - USD ($) $ in Thousands	May 31, 2016	May 31, 2015
Receivables [Abstract]
Trade accounts receivable	$ 140,820	$ 136,208
Allowance for doubtful accounts	(2,907)	(2,980)
Accounts receivable, net	137,913	133,228
Accrued unbilled revenues	$ 18,800	$ 15,000

Inventories (Details) - USD ($) $ in Thousands	May 31, 2016	May 31, 2015
Inventory Disclosure [Abstract]
Raw materials	$ 3,827	$ 4,194
Work in progress	1,743	1,604
Finished goods	2,839	3,178
Services-related consumable supplies	1,509	1,865
Inventory	$ 9,918	$ 10,841

Property, Plant and Equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Property, Plant and Equipment, net
Property, plant and equipment, gross	$ 202,844	$ 190,264
Accumulated depreciation and amortization	(124,168)	(111,008)
Property, plant and equipment, net	78,676	79,256
Depreciation expense	22,900	22,200	$ 19,200
Land
Property, Plant and Equipment, net
Property, plant and equipment, gross	1,735	1,856
Building and improvements
Property, Plant and Equipment, net
Property, plant and equipment, gross	$ 19,364	17,712
Building and improvements \| Minimum
Property, Plant and Equipment, net
Useful Life	30 years
Building and improvements \| Maximum
Property, Plant and Equipment, net
Useful Life	40 years
Office furniture and equipment
Property, Plant and Equipment, net
Property, plant and equipment, gross	$ 8,692	7,934
Office furniture and equipment \| Minimum
Property, Plant and Equipment, net
Useful Life	5 years
Office furniture and equipment \| Maximum
Property, Plant and Equipment, net
Useful Life	8 years
Machinery and equipment
Property, Plant and Equipment, net
Property, plant and equipment, gross	$ 173,053	$ 162,762
Machinery and equipment \| Minimum
Property, Plant and Equipment, net
Useful Life	5 years
Machinery and equipment \| Maximum
Property, Plant and Equipment, net
Useful Life	7 years

Acquisitions and Dispositions - Acquisitions Narrative (Details)	12 Months Ended
	May 31, 2016 USD ($) Entity	May 31, 2015 USD ($) Entity	May 31, 2014 USD ($)
Business Acquisition [Line Items]
Subordinated notes issued	$ 0
Goodwill	169,220,000	$ 166,414,000	$ 130,516,000
Revenue for the period subsequent to closing of the transaction	200,000
Aggregate loss from operation for the period subsequent to closing of transaction	$ 300,000
Minimum
Business Acquisition [Line Items]
Amortization period of intangible assets acquired	2 years
Maximum
Business Acquisition [Line Items]
Amortization period of intangible assets acquired	12 years
Acquisitions in Fiscal 2016
Business Acquisition [Line Items]
Number of entities \| Entity	2
Cash paid	$ 1,784,000
Contingent consideration	991,000
Potential acquisition-related contingent consideration, low end of range	0
Potential acquisition-related contingent consideration, high end of range	300,000.0
Goodwill	$ 2,728,000
Maximum fair value measurement period from the acquisition date	1 year
Acquisitions in Fiscal 2015
Business Acquisition [Line Items]
Number of entities \| Entity		4
Percentage of common stock acquired		100.00%
Cash paid		$ 35,755,000
Contingent consideration		$ 2,255,000
Period over which potential acquisition-related contingent consideration would be payable		3 years
Potential acquisition-related contingent consideration, low end of range		$ 0
Potential acquisition-related contingent consideration, high end of range		3,168,326
Subordinated notes issued		$ 20,505,000
Debt intrument, term		2 years
Goodwill		$ 46,312,000
United States \| Acquisitions in Fiscal 2016
Business Acquisition [Line Items]
Number of entities \| Entity	2
Percentage of common stock acquired	100.00%
Cash paid	$ 1,800,000
Contingent consideration	$ 0
Period over which potential acquisition-related contingent consideration would be payable	4 years
United States \| Acquisitions in Fiscal 2015
Business Acquisition [Line Items]
Number of entities \| Entity		1

Acquisitions and Dispositions - Estimated Fair Value of the Assets Acquired and Liabilities Assumed (Details) $ in Thousands	12 Months Ended
	May 31, 2016 USD ($) Entity	May 31, 2015 USD ($) Entity	May 31, 2014 USD ($)
Consideration transferred:
Subordinated notes issued	$ 0
Estimated fair value of the assets acquired and liabilities assumed
Goodwill	$ 169,220	$ 166,414	$ 130,516
Acquisitions in Fiscal 2016
Consideration transferred:
Number of entities \| Entity	2
Cash paid	$ 1,784
Contingent consideration	991
Consideration paid	2,775
Estimated fair value of the assets acquired and liabilities assumed
Current net assets	180
Debt and other long-term liabilities	(546)
Property, plant and equipment	485
Deferred tax liability	(72)
Intangibles	0
Goodwill	2,728
Net assets acquired	$ 2,775
Acquisitions in Fiscal 2015
Consideration transferred:
Number of entities \| Entity		4
Cash paid		$ 35,755
Subordinated notes issued		20,505
Contingent consideration		2,255
Consideration paid		58,515
Estimated fair value of the assets acquired and liabilities assumed
Current net assets		2,770
Debt and other long-term liabilities		(5,889)
Property, plant and equipment		7,395
Deferred tax liability		(2,467)
Intangibles		10,394
Goodwill		46,312
Net assets acquired		$ 58,515

Acquisitions and Dispositions - Dispositions Narrative (Details) $ in Thousands		12 Months Ended
	May 22, 2015 USD ($) subsidiary	May 31, 2016 USD ($)	May 31, 2015 USD ($) subsidiary	May 31, 2014 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Charges associated with the exit of foreign operations		$ 0	$ 2,516	$ 0
International \| Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations \| Disposal Of Foreign Subsidiaries
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of foreign subsidiaries sold and held-for-sale \| subsidiary			3
Disposal group, percentage of assets to consolidated assets			0.60%
Disposal group, percentage of liabilities to consolidated liabilities			0.30%
International \| Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations \| Disposal Of Foreign Subsidiaries \| Russia
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of subsidiaries sold \| subsidiary	1
Charges associated with the exit of foreign operations	$ (400)
International \| Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations \| Disposal Of Foreign Subsidiaries \| Russia and Japan
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Charges associated with the exit of foreign operations			$ (2,500)
Impairment charges on subsidiaries held-for-sale			$ 2,100

Acquisitions and Dispositions - Acquisition-Relate Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Business Acquisition [Line Items]
Adjustments to fair value of contingent consideration liabilities	$ (2,066)	$ (5,382)	$ (3,937)
Acquisition-related (benefit) expense, net	(1,453)	(5,167)	(2,657)
Acquisitions in Fiscal 2016
Business Acquisition [Line Items]
Due diligence, professional fees and other transaction costs	629
Adjustments to fair value of contingent consideration liabilities	(2,082)
Acquisition-related (benefit) expense, net	$ (1,453)
Acquisitions in Fiscal 2015
Business Acquisition [Line Items]
Due diligence, professional fees and other transaction costs		215
Adjustments to fair value of contingent consideration liabilities		(5,382)
Acquisition-related (benefit) expense, net		$ (5,167)
Acquisitions in Fiscal 2014
Business Acquisition [Line Items]
Due diligence, professional fees and other transaction costs			1,280
Adjustments to fair value of contingent consideration liabilities			(3,937)
Acquisition-related (benefit) expense, net			$ (2,657)

Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
Goodwill (Details) - USD ($) $ in Thousands	May 31, 2016	May 31, 2015	May 31, 2014
Changes in the carrying amount of goodwill
Balance at the beginning of the period	$ 166,414	$ 130,516
Goodwill acquired (disposed) during the year	2,354	43,466
Adjustments to preliminary purchase price allocations	270	3,162
Foreign currency translation	182	(10,730)
Balance at the end of the period	169,220	166,414
Services
Changes in the carrying amount of goodwill
Balance at the beginning of the period	117,279	73,767
Goodwill acquired (disposed) during the year	2,728	41,986
Adjustments to preliminary purchase price allocations	270	3,529
Foreign currency translation	(594)	(2,003)
Balance at the end of the period	119,683	117,279
International
Changes in the carrying amount of goodwill
Balance at the beginning of the period	35,938	43,552
Goodwill acquired (disposed) during the year	(374)	1,480
Adjustments to preliminary purchase price allocations	0	(367)
Foreign currency translation	776	(8,727)
Balance at the end of the period	36,340	35,938
Goodwill, cumulative impairment charge	9,900	9,900	$ 9,900
Products
Changes in the carrying amount of goodwill
Balance at the beginning of the period	13,197	13,197
Goodwill acquired (disposed) during the year	0	0
Adjustments to preliminary purchase price allocations	0	0
Foreign currency translation	0	0
Balance at the end of the period	$ 13,197	$ 13,197

Intangible Assets - Gross Carrying Amount and Accumulated Amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Intangible assets
Gross Amount	$ 117,419	$ 115,427
Accumulated Amortization	(73,927)	(64,151)
Net Carrying Amount	43,492	51,276
Amortization expense	9,600	11,100	$ 9,200
Customer relationships
Intangible assets
Gross Amount	81,262	81,101
Accumulated Amortization	(47,747)	(41,009)
Net Carrying Amount	$ 33,515	40,092
Customer relationships \| Minimum
Intangible assets
Useful Life (Years)	5 years
Customer relationships \| Maximum
Intangible assets
Useful Life (Years)	12 years
Software/Technology
Intangible assets
Useful Life (Years)	3 years
Gross Amount	$ 17,539	15,738
Accumulated Amortization	(11,855)	(10,290)
Net Carrying Amount	5,684	5,448
Amortization expense	$ 1,000	900	$ 900
Software/Technology \| Minimum
Intangible assets
Useful Life (Years)	3 years
Software/Technology \| Maximum
Intangible assets
Useful Life (Years)	15 years
Covenants not to compete
Intangible assets
Gross Amount	$ 10,791	11,678
Accumulated Amortization	(9,290)	(8,605)
Net Carrying Amount	$ 1,501	3,073
Covenants not to compete \| Minimum
Intangible assets
Useful Life (Years)	2 years
Covenants not to compete \| Maximum
Intangible assets
Useful Life (Years)	5 years
Other
Intangible assets
Gross Amount	$ 7,827	6,910
Accumulated Amortization	(5,035)	(4,247)
Net Carrying Amount	$ 2,792	$ 2,663
Other \| Minimum
Intangible assets
Useful Life (Years)	2 years
Other \| Maximum
Intangible assets
Useful Life (Years)	5 years

Intangible Assets - Expected Amortization Expense (Details) - USD ($) $ in Thousands	May 31, 2016	May 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
2017	$ 8,618
2018	7,302
2019	6,119
2020	4,495
2021	4,238
Thereafter	12,720
Net Carrying Amount	$ 43,492	$ 51,276

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	May 31, 2016	May 31, 2015
Payables and Accruals [Abstract]
Accrued salaries, wages and related employee benefits	$ 31,566	$ 26,053
Contingent consideration	1,029	3,543
Accrued worker compensation and health benefits	4,834	3,630
Deferred revenues	3,332	3,841
Legal settlement accrual	6,320	0
Other accrued expenses	15,902	18,847
Total accrued expenses and other current liabilities	$ 62,983	$ 55,914

Long-Term Debt - Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands	May 31, 2016	May 31, 2015
Debt Instrument [Line Items]
Total debt	$ 85,009	$ 113,459
Less: Current portion	(12,553)	(17,902)
Long-term debt, net of current portion	72,456	95,557
Senior credit facility
Debt Instrument [Line Items]
Total debt	68,999	83,062
Notes payable
Debt Instrument [Line Items]
Total debt	10,111	24,632
Other
Debt Instrument [Line Items]
Total debt	$ 5,899	$ 5,765

Long-Term Debt - Narrative (Details)	12 Months Ended
Long-Term Debt - Narrative (Details)	May 31, 2016 USD ($) Quarter	Oct. 31, 2014 USD ($)	Oct. 30, 2014 USD ($)
Senior credit facility
Long-Term Debt
Maximum borrowing capacity		$ 175,000,000.0	$ 125,000,000.0
Higher borrowing capacity option		225,000,000.0
Maximum borrowing capacity in non-U.S. Dollar currencies		30,000,000.0
Maximum amount available for the issuance of letters of credit		$ 10,000,000.0
Long-term Line of Credit	$ 69,000,000
Outstanding letters of credit	4,800,000
Capitalized debt modification costs	$ 700,000
Number of consecutive fiscal quarters used for calculating Funded Debt Leverage Ratio \| Quarter	4
Funded Debt Leverage Ratio at which the entity will bear the maximum interest rate margin	2.0
Additional interest rate margin if Funded Debt Leverage Ratio exceeds threshold (as a percent)	2.00%
Preceding period used for calculating Interest Coverage Ratio	12 months
Senior credit facility \| Minimum
Long-Term Debt
Interest Coverage Ratio	3.0
Senior credit facility \| Maximum
Long-Term Debt
Funded Debt Leverage Ratio at which the entity will have the benefit of lowest interest margin	0.5
Funded Debt Leverage Ratio for additional interest payment	3.25
Senior credit facility \| LIBOR
Long-Term Debt
Reference rate, description	LIBOR
Senior credit facility \| LIBOR \| Minimum
Long-Term Debt
Margin (as a percent)	1.00%
Senior credit facility \| LIBOR \| Maximum
Long-Term Debt
Margin (as a percent)	1.75%
Senior credit facility \| Base rate
Long-Term Debt
Reference rate, description	base rate
Senior credit facility \| Base rate \| Minimum
Long-Term Debt
Margin (as a percent)	(1.25%)
Senior credit facility \| Base rate \| Maximum
Long-Term Debt
Margin (as a percent)	(0.375%)
Notes payable
Long-Term Debt
Interest rate, minimum (as a percent)	0.00%
Interest rate, maximum (as a percent)	4.00%
Notes payable \| Minimum
Long-Term Debt
Maturity term from the date of acquisition	2 years
Market interest rate (as a percent)	2.00%
Notes payable \| Maximum
Long-Term Debt
Maturity term from the date of acquisition	5 years
Market interest rate (as a percent)	4.00%

Long-Term Debt - Principal Payments Due Under All Borrowing Agreements (Details) - USD ($) $ in Thousands	May 31, 2016	May 31, 2015
Debt Disclosure [Abstract]
2017	$ 12,553
2018	881
2019	751
2020	69,446
2021	294
Thereafter	1,084
Total debt	$ 85,009	$ 113,459

Fair Value Measurements (Details) - Recurring basis - USD ($) $ in Thousands	May 31, 2016	May 31, 2015
Liabilities:
Contingent consideration	$ 2,075	$ 6,411
Total Liabilities	2,075	6,411
Level 1
Liabilities:
Contingent consideration	0	0
Total Liabilities	0	0
Level 2
Liabilities:
Contingent consideration	0	0
Total Liabilities	0	0
Level 3
Liabilities:
Contingent consideration	2,075	6,411
Total Liabilities	$ 2,075	$ 6,411

Share-Based Compensation Narrative (Details) $ in Thousands	12 Months Ended
Share-Based Compensation Narrative (Details) $ in Thousands	May 31, 2016 USD ($) plan shares	May 31, 2015 USD ($) shares	May 31, 2014 USD ($) shares	May 31, 2013 shares
Share-based compensation
Number of employee stock ownership plans \| plan	2
Stock option awards
Share-based compensation
Stock options outstanding (in shares)	2,232,000	2,287,000	2,352,000	2,464,000
Recognized share-based compensation expense \| $	$ 100	$ 100	$ 700
Stock options granted (in shares)	0	0	0
Additional disclosures
Cash proceeds from options exercised \| $	$ 543	$ 750	$ 996
Aggregate intrinsic value of options exercised \| $	$ 658	563	1,247
Restricted stock unit awards
Share-based compensation
Unvested restricted stock units outstanding (in shares)	902,000
Recognized share-based compensation expense \| $	$ 4,400	$ 4,700	$ 4,000
2007 Plan
Share-based compensation
Number of awards that may be granted (in shares)	0
2009 Plan
Share-based compensation
Number of awards that may be granted (in shares)	658,000
Number of shares authorized for grants (in shares)	2,286,000

Share-Based Compensation - Summary of Stock Option Activity and Weighted Average Exercise Prices (Details) - Stock option awards - $ / shares	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Common Stock Options (shares)
Outstanding at beginning of year: (in shares)	2,287,000	2,352,000	2,464,000
Granted (in shares)	0	0	0
Exercised (in shares)	(55,000)	(65,000)	(103,000)
Expired or forfeited (in shares)	0	0	(9,000)
Outstanding at end of year: (in shares)	2,232,000	2,287,000	2,352,000
Weighted Average Exercise Price (in dollar per share)
Outstanding at beginning of year: (in dollars per share)	$ 13.13	$ 13.09	$ 12.93
Granted (in dollars per share)	0.00	0.00	0.00
Exercised (in dollars per share)	9.87	11.54	9.67
Expired or forfeited (in dollars per share)	0.00	0.00	10.03
Outstanding at end of year: (in dollars per share)	$ 13.21	$ 13.13	$ 13.09

Share-Based Compensation - Summary of Options Outstanding and Exercisable (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	May 31, 2016 USD ($) $ / shares shares
Options Outstanding
Total Options Outstanding (in shares) \| shares	2,232
Options Exercisable
Number Exercisable (in shares) \| shares	2,232
Aggregate Intrinsic Value
Options Outstanding (in dollars) \| $	$ 25,887
Options Exercisable (in dollars) \| $	$ 25,887
$6.15-$11.54
Options Outstanding
Total Options Outstanding (in shares) \| shares	137
Weighted Average Remaining Life (Years)	2 years 3 months 18 days
Weighted Average Exercise Price (in dollars per share)	$ 9.09
Options Exercisable
Number Exercisable (in shares) \| shares	137
Weighted Average Exercise Price (in dollars per share)	$ 9.09
Aggregate Intrinsic Value
Range of Exercise Prices, Lower Limit	6.15
Range of Exercise Prices, Upper Limit	$ 11.54
$13.46-$22.35
Options Outstanding
Total Options Outstanding (in shares) \| shares	2,095
Weighted Average Remaining Life (Years)	3 years 2 months 12 days
Weighted Average Exercise Price (in dollars per share)	$ 13.48
Options Exercisable
Number Exercisable (in shares) \| shares	2,095
Weighted Average Exercise Price (in dollars per share)	$ 13.48
Aggregate Intrinsic Value
Range of Exercise Prices, Lower Limit	13.46
Range of Exercise Prices, Upper Limit	$ 22.35

Share-Based Compensation - Restricted Stock Units Awards (Details) shares in Thousands, $ in Millions	3 Months Ended	12 Months Ended
	Aug. 31, 2015 shares	May 31, 2016 USD ($) director shares	May 31, 2015 USD ($) director shares	May 31, 2014 USD ($) director shares
Share-based compensation
Income tax benefit recognized on share-based compensation \| $		$ 2.2	$ 2.3	$ 2.3
Non-employee directors
Share-based compensation
Number of non-employee directors to whom fully vested common stock is granted \| director			5	5
Restricted stock unit awards
Share-based compensation
Recognized share-based compensation expense \| $		4.4	$ 4.7	$ 4.0
Unrecognized compensation cost, net of estimated forfeitures, related to restricted stock unit awards \| $		$ 7.0
Weighted-average period over which unrecognized compensation cost is expected to be recognized		2 years 1 month 3 days
Number of restricted stocks units granted (in shares)		264	192	295
Number of restricted stocks vested (in shares)		223	232	178
Fair value of shares vested \| $		$ 3.5	$ 5.2	$ 3.3
Number of restricted stocks forfeited (in shares)		30	24	44
Unvested restricted stock units outstanding (in shares)		902
Restricted stock unit awards \| Non-employee directors
Share-based compensation
Fair value of shares vested \| $		$ 0.5	$ 0.4	$ 0.4
Number of fully vested common stock granted (in shares)		28	21	19
Number of non-employee directors to whom fully vested common stock is granted \| director		5
Performance restricted stock units \| Executive and senior officers
Share-based compensation
Recognized share-based compensation expense \| $		$ 1.6	$ 1.5	$ 1.2
Unrecognized compensation cost, net of estimated forfeitures, related to restricted stock unit awards \| $		$ 3.2
Weighted-average period over which unrecognized compensation cost is expected to be recognized		3 years 8 months 12 days
Unvested restricted stock units outstanding (in shares)		328
Performance restricted stock units \| Executive and senior officers \| Fiscal 2014 Grants
Share-based compensation
Requisite service period		3 years
Performance restricted stock units \| Executive and senior officers \| Fiscal 2015 Grants
Share-based compensation
Requisite service period		3 years
Performance restricted stock units \| Executive and senior officers \| Fiscal 2016 Grants
Share-based compensation
Number of fully vested common stock granted (in shares)	154
Requisite service period		5 years
Number of additional shares authorized for grants (in shares)	85
Number of shares authorized for grants (in shares)		239
Performance Restricted Stock Units with one year EPS performance condition \| Executive and senior officers \| Fiscal 2014 Grants
Share-based compensation
Performance period		1 year
Payout for the fiscal 2014 market condition awards, percentage of target		170.00%
Performance Restricted Stock Units with two year EPS performance condition \| Executive and senior officers \| Fiscal 2014 Grants
Share-based compensation
Performance period		2 years
Payout for the fiscal 2014 market condition awards, percentage of target		105.00%
Performance Restricted Stock Units with three year EPS performance condition \| Executive and senior officers \| Fiscal 2014 Grants
Share-based compensation
Performance period		3 years

Income Taxes - Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Income (loss) before provision for income taxes from:
U.S. operations	$ 27,772	$ 26,893	$ 25,433
Foreign operations	10,643	(1,162)	9,670
Income before provision for income taxes	38,415	25,731	35,103
Current
Federal	9,156	8,489	8,836
States and local	1,537	1,177	1,689
Foreign	3,672	1,493	2,484
Reserve for uncertain tax positions	(529)	(48)	59
Total current	13,836	11,111	13,068
Deferred
Federal	82	(145)	(53)
States and local	(51)	(126)	395
Foreign	(557)	(2,416)	(967)
Total deferred	(526)	(2,687)	(625)
Net change in valuation allowance	455	1,316	85
Net deferred	(71)	(1,371)	(540)
Provision for income taxes	13,765	9,740	12,528
Reconciliation of income tax expense at the statutory rate to the effective income tax expense
Federal tax at statutory rate	13,445	9,006	12,286
State taxes, net of federal benefit	966	683	1,355
Foreign tax	(610)	(517)	(1,868)
Contingent consideration	(425)	(914)	24
Permanent differences	245	196	531
Other	(311)	(30)	115
Change in valuation allowance	455	1,316	85
Provision for income taxes	$ 13,765	$ 9,740	$ 12,528
Reconciliation of the federal income tax expense (as a percent)
Federal tax at statutory rate	35.00%	35.00%	35.00%
State taxes, net of federal benefit	2.50%	2.70%	3.90%
Foreign tax	(1.60%)	(2.00%)	(5.30%)
Contingent consideration	(1.10%)	(3.60%)	0.10%
Permanent differences	0.60%	0.80%	1.50%
Other	(0.80%)	(0.10%)	0.30%
Change in valuation allowance	1.20%	5.10%	0.20%
Total provision for income taxes	35.80%	37.90%	35.70%

Income Taxes - Deferred Income Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015
Deferred income tax assets
Allowance for doubtful accounts	$ 940	$ 1,036
Inventory	518	796
Intangible assets	1,641	1,254
Accrued expenses	4,668	3,455
Net operating loss carryforward	4,036	4,738
Capital lease obligations	1,167	379
Capital losses	719	0
Deferred share-based compensation	6,477	6,241
Other	440	370
Deferred income tax assets	20,606	18,269
Valuation allowance	(3,397)	(3,238)
Net deferred income tax assets	17,209	15,031
Deferred income tax liabilities
Property and equipment	(9,785)	(8,214)
Goodwill	(12,535)	(10,728)
Intangible assets	(5,989)	(6,677)
Other	(12)	(44)
Deferred income tax liabilities	(28,321)	(25,663)
Net deferred income taxes	(11,112)	(10,632)
Changes in company's gross unrecognized tax benefits, excluding interest and penalties
Balance at June 1	763	1,016
Additions for tax positions related to the current fiscal year	29	30
Additions for tax positions related to prior years	52	0
Decreases for tax positions related to prior years	(23)	(1)
Impact of foreign exchange fluctuation	(91)	(112)
Settlements	(29)	(50)
Reductions related to the expiration of statutes of limitations	(398)	(120)
Balance at May 31	$ 303	$ 763

Income Taxes - Narrative (Details) - USD ($)	3 Months Ended								12 Months Ended
Income Taxes - Narrative (Details) - USD ($)	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2014	May 31, 2016	May 31, 2015	May 31, 2014
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ (3,397,000)				$ (3,238,000)				$ (3,397,000)	$ (3,238,000)
Unrecognized tax benefits including penalties and interest, that would affect the effective tax rate, if recognized	400,000				1,100,000				400,000	1,100,000
Anticipated decrease in unrecognized tax benefits, excluding interest and penalties within the next 12 months	200,000								200,000
Net income (loss) of foreign subsidiaries	2,764,000	$ 3,593,000	$ 11,425,000	$ 6,872,000	$ 2,171,000	$ 1,817,000	$ 10,427,000	$ 1,666,000	24,654,000	16,081,000	$ 22,518,000
Deferred tax liability recognized for the remittance of undistributed international earnings	0								0
Federal \| Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Net operating losses	300,000								300,000
State
Operating Loss Carryforwards [Line Items]
Net operating losses	3,600,000								3,600,000
Foreign
Operating Loss Carryforwards [Line Items]
Net operating losses	12,100,000								12,100,000
Increase in valuation allowance due to losses in foreign subsidiaries									200,000
Net income (loss) of foreign subsidiaries									7,500,000	$ (800,000)
Foreign \| Expiration Period 2021-2036
Operating Loss Carryforwards [Line Items]
Net operating losses	1,700,000								1,700,000
Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations \| Disposal Of Foreign Subsidiaries \| State and Foreign
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ (3,400,000)								$ (3,400,000)

Employee Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
Employee Benefit Plans (Details) - USD ($) $ in Millions	May 31, 2016	May 31, 2015	May 31, 2014
401(k) savings plan
Minimum age for employees to contribute catch up contributions under IRS limits	50 years
Continuous service period required for eligibility of employees to participate under the plan	6 months
Maximum Company match amount of employee contributions matched up to 6% of annual compensation (as a percent)	50.00%
Maximum percentage of employee's annual compensation for which the company contributes a matching contribution (as a percent)	6.00%
Vesting period for employer matching contribution	5 years
Contribution under 401(k) savings plan	$ 3.3	$ 2.8	$ 2.5
Amount of employers contribution to the union plan	$ 0.2	$ 0.2	$ 0.1

Related Party Transactions (Details) - Shareholder and officer $ in Millions	12 Months Ended
	May 31, 2016 USD ($)
Related Party Transactions
Total rent payments	$ 0.9
France
Related Party Transactions
Total rent payments	0.2
Brazil
Related Party Transactions
Total rent payments	$ 0.1

Obligations under Capital Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015
Obligations under capital leases
Net book value of assets under capital lease	$ 19,800	$ 19,900
Future minimum lease payments
2017	9,112
2018	6,491
2019	3,810
2020	1,520
2021	134
Thereafter	122
Total minimum lease payments	21,189
Less: amount representing interest	(1,422)
Present value of minimum lease payments	19,767
Less: current portion of obligations under capital leases	(7,835)	(8,646)
Obligations under capital leases, net of current portion	11,932	$ 10,717
Minimum
Obligations under capital leases
Required monthly payments	$ 1
Effective interest rate (as a percent)	1.00%
Maximum
Obligations under capital leases
Required monthly payments	$ 81
Effective interest rate (as a percent)	7.30%

Commitments and Contingencies (Details)	3 Months Ended	12 Months Ended
Commitments and Contingencies (Details)	May 31, 2016 USD ($)	May 31, 2016 USD ($) plaintiff	May 31, 2015 USD ($)	May 31, 2014 USD ($)
Future minimum lease payments
2017	$ 9,956,000	$ 9,956,000
2018	7,903,000	7,903,000
2019	6,580,000	6,580,000
2020	5,219,000	5,219,000
2021	4,112,000	4,112,000
Thereafter	13,039,000	13,039,000
Total	46,809,000	46,809,000
Total rent expense		11,200,000	$ 10,600,000	$ 9,500,000
Litigation
Payroll taxes and other cost related to settlement		6,320,000	$ 0	$ 0
Consolidated class and collective action lawsuit
Litigation
Litigation settlement		$ 6,000,000
Payroll taxes and other cost related to settlement	6,300,000
Loss Contingency, Number of Plaintiffs \| plaintiff		4,900
Lawsuits for alleged quality defects
Litigation
Verbal demand for damages		$ 6,000,000
Dispute with former owner of company's French subsidiary \| French Subsidiary
Litigation
Litigation settlement		400,000
Acquisition-related contingencies
Litigation
Potential acquisition-related contingent consideration, low end of range	0	0
Potential acquisition-related contingent consideration, high end of range	$ 16,600,000	$ 16,600,000
Period over which potential acquisition-related contingent consideration would be payable		4 years

Segment Disclosure - Financial Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	May 31, 2016 USD ($)	Feb. 29, 2016 USD ($)	Nov. 30, 2015 USD ($)	Aug. 31, 2015 USD ($)	May 31, 2015 USD ($)	Feb. 28, 2015 USD ($)	Nov. 30, 2014 USD ($)	Aug. 31, 2014 USD ($)	May 31, 2016 USD ($) Operating_Segment	May 31, 2015 USD ($)	May 31, 2014 USD ($)
Segment Reporting [Abstract]
Number of operating segments \| Operating_Segment									3
Financial information by segment
Revenue	$ 184,187	$ 160,355	$ 194,786	$ 179,853	$ 174,686	$ 163,100	$ 206,893	$ 166,573	$ 719,181	$ 711,252	$ 623,447
Gross Profit	52,000	42,809	56,925	51,274	44,966	38,734	59,039	41,994	203,008	184,733	172,943
Income from operations	4,918	$ 5,758	$ 19,569	$ 12,932	4,627	$ 3,870	$ 18,192	$ 3,664	43,177	30,353	38,295
Depreciation and amortization									32,474	33,286	28,429
Intangible assets, net	43,492				51,276				43,492	51,276
Total assets	482,675				471,727				482,675	471,727
Operating segments \| Services
Financial information by segment
Revenue									553,279	540,224	443,229
Gross Profit									145,262	135,201	114,182
Income from operations									52,552	49,142	43,221
Depreciation and amortization									22,725	22,268	17,794
Intangible assets, net	19,022				24,598				19,022	24,598
Total assets	308,008				301,031				308,008	301,031
Operating segments \| International
Financial information by segment
Revenue									143,025	146,953	161,395
Gross Profit									43,613	34,572	44,893
Income from operations									9,293	(575)	10,238
Depreciation and amortization									7,774	8,451	8,065
Intangible assets, net	17,703				19,482				17,703	19,482
Total assets	132,643				126,643				132,643	126,643
Operating segments \| Products and Systems
Financial information by segment
Revenue									30,293	31,255	33,544
Gross Profit									14,022	14,314	14,495
Income from operations									2,688	2,461	2,552
Depreciation and amortization									2,323	2,426	2,373
Intangible assets, net	6,054				7,004				6,054	7,004
Total assets	31,596				35,464				31,596	35,464
Corporate and eliminations
Financial information by segment
Revenue									(7,416)	(7,180)	(14,721)
Gross Profit									111	646	(627)
Income from operations									(21,356)	(20,675)	(17,716)
Depreciation and amortization									(348)	141	$ 197
Intangible assets, net	713				192				713	192
Total assets	$ 10,428				$ 8,589				$ 10,428	$ 8,589

Segment Disclosure - Revenue and Long-lived Assets (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2014	May 31, 2016	May 31, 2015	May 31, 2014
Revenue and long-lived assets by geographic area
Revenue	$ 184,187	$ 160,355	$ 194,786	$ 179,853	$ 174,686	$ 163,100	$ 206,893	$ 166,573	$ 719,181	$ 711,252	$ 623,447
Long-lived assets	291,388				296,946				291,388	296,946
United States
Revenue and long-lived assets by geographic area
Revenue									519,361	491,818	403,001
Long-lived assets	186,543				190,997				186,543	190,997
Other Americas
Revenue and long-lived assets by geographic area
Revenue									67,809	68,628	55,120
Long-lived assets	29,743				31,558				29,743	31,558
Europe
Revenue and long-lived assets by geographic area
Revenue									118,566	137,071	143,931
Long-lived assets	75,102				73,744				75,102	73,744
Asia-Pacific
Revenue and long-lived assets by geographic area
Revenue									13,445	13,735	$ 21,395
Long-lived assets	$ 0				$ 647				$ 0	$ 647

Selected Quarterly Financial Information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2014	May 31, 2016	May 31, 2015	May 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 184,187	$ 160,355	$ 194,786	$ 179,853	$ 174,686	$ 163,100	$ 206,893	$ 166,573	$ 719,181	$ 711,252	$ 623,447
Gross Profit	52,000	42,809	56,925	51,274	44,966	38,734	59,039	41,994	203,008	184,733	172,943
Income from operations	4,918	5,758	19,569	12,932	4,627	3,870	18,192	3,664	43,177	30,353	38,295
Net income attributable to Mistras Group, Inc.	$ 2,764	$ 3,593	$ 11,425	$ 6,872	$ 2,171	$ 1,817	$ 10,427	$ 1,666	$ 24,654	$ 16,081	$ 22,518
Earnings per common share:
Basic (in dollars per share)	$ 0.10	$ 0.12	$ 0.40	$ 0.24	$ 0.08	$ 0.06	$ 0.36	$ 0.06	$ 0.85	$ 0.56	$ 0.79
Diluted (in dollars per share)	$ 0.09	$ 0.12	$ 0.39	$ 0.23	$ 0.07	$ 0.06	$ 0.35	$ 0.06	$ 0.82	$ 0.54	$ 0.77

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Subsequent Events (Details) - Subsequent Event - Asset Protection Business $ in Millions	2 Months Ended
	Aug. 15, 2016 USD ($) Entity
Subsequent Event [Line Items]
Number of entities \| Entity	2
Cash paid	$ 1.2
Business combinations, deferred purchase price	0.3
Potential acquisition-related contingent consideration, high end of range	$ 0.6
Period over which potential acquisition-related contingent consideration would be payable	3 years