Business Combinations [Abstract] Due diligence, professional fees and other transaction costs Business Combination, Acquisition Related Costs Adjustments to fair value of contingent consideration liabilities Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability Acquisition-related expense (benefit), net Acquisition Related Costs and Fair Value Adjustments to Initial Purchase Price Allocation This element represents acquisition-related costs incurred in connection with business combinations which costs have been expensed during the period. This also includes adjustments to the fair value of the initial purchase price allocation for acquisitions including, but not limited to, changes in contingent consideration liabilities and other liabilities, accounts receivable, inventory, fixed assets, other assets, and other acquisition-related intangible assets. Acquisition-related costs also include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities. Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Fiscal 2018 Acquisitions Acquisitions in Fiscal 2018 [Member] Acquisitions in Fiscal 2018 Fiscal 2017 Acquisitions Acquisitions in Fiscal 2017 [Member] Acquisitions in Fiscal 2017 Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Customer Relationships and Covenants Not To Compete Customer Relationships and Noncompete Agreements [Member] Customer Relationships and Noncompete Agreements Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] United States UNITED STATES Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Services Services [Member] Represents Services, a business segment of the entity. Acquisitions Business Acquisition [Line Items] Number of acquisitions Number of Businesses Acquired Cash paid for acquisitions Payments to Acquire Businesses, Gross Contingent consideration from acquisitions Business Combination, Contingent Consideration, Liability Goodwill Goodwill Other intangible assets acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Current Assets Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Accounts receivable, net Receivables, Net, Current Inventories Inventory, Net Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Total current assets Assets, Current Property, plant and equipment, net Property, Plant and Equipment, Net Intangible assets, net Intangible Assets, Net (Excluding Goodwill) Deferred income taxes Deferred Tax Assets, Net of Valuation Allowance, Noncurrent Other assets Other Assets, Noncurrent Total assets Assets LIABILITIES AND EQUITY Liabilities and Equity [Abstract] Current Liabilities Liabilities, Current [Abstract] Accounts payable Accounts Payable, Current Accrued expenses and other current liabilities Accrued Liabilities Deferred Revenues and Contingent Consideration Liabilities, Current Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Also includes the fair value of contingent consideration liabilities and the carrying amount of consideration received or receivable as of the balance sheet date on potential earnings that were not recognized as revenue in conformity with GAAP, and which are expected to be recognized as such within one year or the normal operating cycle, if longer, including sales, license fees, and royalties, but excluding interest income. Current portion of long-term debt Long-term Debt, Current Maturities Current portion of capital lease obligations Capital Lease Obligations, Current Income taxes payable Accrued Income Taxes, Current Total current liabilities Liabilities, Current Long-term debt, net of current portion Long-term Debt, Excluding Current Maturities Obligations under capital leases, net of current portion Capital Lease Obligations, Noncurrent Deferred income taxes Deferred Tax Liabilities, Net, Noncurrent Other long-term liabilities Other Liabilities, Noncurrent Total liabilities Liabilities Commitments and contingencies Commitments and Contingencies Equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Preferred stock, 10,000,000 shares authorized Preferred Stock, Value, Issued Common stock, $0.01 par value, 200,000,000 shares authorized, 28,313,744 and 28,294,968 shares issued Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total Mistras Group, Inc. stockholders’ equity Stockholders' Equity Attributable to Parent Non-controlling interests Stockholders' Equity Attributable to Noncontrolling Interest Total equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total liabilities and equity Liabilities and Equity Receivables [Abstract] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Billing Status, Type [Axis] Billing Status, Type [Axis] Receivables Billing Status [Domain] Receivables Billing Status [Domain] Unbilled Revenues Unbilled Revenues [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Trade accounts receivable Accounts Receivable, Gross, Current Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Share-Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Goodwill Schedule of Goodwill [Table Text Block] Payables and Accruals [Abstract] Accrued Expenses and Other Current Liabilities Accrued Liabilities Deferred Revenues and Contingent Consideration Liabilities Current Disclosure [Text Block] The entire disclosure for accrued liabilities, deferred revenues, and the fair value of contingent consideration liabilities at the end of the reporting period. Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Performance Restricted Stock Units Performance Shares [Member] Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] Executive and Senior Officers Executive and Senior Officers [Member] Represents information pertaining to the executives and senior officers of the reporting entity. Vesting [Axis] Vesting [Axis] Vesting [Domain] Vesting [Domain] Anniversary 1 Share-based Compensation Award, Tranche One [Member] Anniversary 2 Share-based Compensation Award, Tranche Two [Member] Anniversary 3 Share-based Compensation Award, Tranche Three [Member] Anniversary 4 Share-based Compensation Award, Tranche Four [Member] Share-based Compensation Award, Tranche Four Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Accrued expenses and other liabilities Accrued Expenses and Other Current Liabilities [Member] Accrued Expenses and Other Current Liabilities Share-based compensation Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Performance period (years) Share Based Compensation Arrangement by Share Based Payment Award, Award Performance Period Represents the performance period of the entity, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Number of performance award metrics Share-Based Compensation Arrangement By Share-Based Payment Award, Number Of Award Metrics Share-Based Compensation Arrangement By Share-Based Payment Award, Number Of Award Metrics Requisite service period (years) Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period Award vesting rights, percentage Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage Increase (decrease) in nonvested shares authorized (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Increase (Decrease) Adjustments in Period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Increase (Decrease) Adjustments in Period Accrued liability related to discretionary PRSUs Accrued Liabilities, Current Recognized share-based compensation expense (benefit) Allocated Share-based Compensation Expense Unrecognized compensation cost Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options Nonvested shares outstanding (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Weighted-average period over which unrecognized compensation cost is expected to be recognized (years) Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Document and Entity Information Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Document Type Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Current Fiscal Year End Date Current Fiscal Year End Date Entity Current Reporting Status Entity Current Reporting Status Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] 2007 Plan Stock Option Plan 2007 [Member] Represents the incentive stock options plan as awarded by the company to the employees and directors under the two employee stock ownership plans. 2009 Plan Long Term Incentive Plan 2009 [Member] Represents information pertaining to 2009 Long-Term Incentive Plan, which becomes effective upon the closing of the IPO. Number of employee stock ownership plans (plan) Number Of Employee Share-Based Plans Number Of Employee Share-Based Plans Number of awards that may be granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Schedule of Stock Option Activity, Weighted Average Exercise Prices and Options Outstanding Share-based Compensation, Stock Options, Activity [Table Text Block] Schedule of Company's Outstanding, Nonvested Restricted Share Units and Performance Restricted Stock Units Schedule of Other Share-based Compensation, Activity [Table Text Block] Earnings Per Share [Abstract] Earnings per Share Earnings Per Share [Text Block] Restricted Stock Units Restricted Stock Units (RSUs) [Member] Non-employee directors Director [Member] Unrecognized compensation cost, net of estimated forfeitures Number of fully vested common stock granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted Number of non-employee directors to whom fully vested common stock is granted (director) Share Based Compensation Arrangement by Share Based Payment Award, Number of Non Employee Directors to whom Award is Granted Represents the number of non-employee directors to whom fully vested common stock is granted. Fair value of shares vested Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Shares vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Revenue from Contract with Customer [Abstract] Revenue Revenue from Contract with Customer [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Principles of Consolidation Consolidation, Policy [Policy Text Block] Reclassification Reclassification, Policy [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Revenue Revenue Recognition, Policy [Policy Text Block] Fair Value Measurements Fair Value Measurement, Policy [Policy Text Block] Schedule of Acquisition-Related Expenses Schedule of Business Combination Acquisition Related Costs [Table Text Block] Tabular disclosure of acquisition-related costs. Segment Reporting [Abstract] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Other Americas Other Americas [Member] Represents the information pertaining to North and South America excluding the United States. Europe Europe [Member] Asia-Pacific Asia Pacific [Member] Revenue and long-lived assets by geographic area Revenues from External Customers and Long-Lived Assets [Line Items] Revenues Revenue, Net Commitments and Contingencies Disclosure [Abstract] Loss Contingencies [Table] Loss Contingencies [Table] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Consolidated class and collective action lawsuit Consolidated class and collective action lawsuit [Member] Consolidated class and collective action lawsuit [Member] Dispute with former owner of company's French subsidiary Dispute with former owner of company's French subsidiary [Member] Dispute with former owner of company's French subsidiary Defective ultrasound inspection system Damages from Product Defects [Member] Acquisition-related contingencies Acquisition Related Contingencies [Member] Represents the contingencies pertaining to business acquisitions by the entity. Litigation Status [Axis] Litigation Status [Axis] Litigation Status [Domain] Litigation Status [Domain] Settled Litigation Settled Litigation [Member] Pending Litigation Pending Litigation [Member] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Affiliated Entity Affiliated Entity [Member] Litigation Case [Axis] Litigation Case [Axis] Litigation Case [Domain] Litigation Case [Domain] AGL Services Company v. Mistras Group AGL Services Company v Mistras Group [Member] AGL Services Company v Mistras Group Triumph Aerostructures-Vought Aircraft Division v. Mistras Group Triumph Aerostructures-Vought Aircraft Division v Mistras Group [Member] Triumph Aerostructures-Vought Aircraft Division v Mistras Group Products and Services [Axis] Products and Services [Axis] Products and Services [Domain] Products and Services [Domain] Ultrasonic Inspection System Ultrasonic Inspection System [Member] Ultrasonic Inspection System Litigation Loss Contingencies [Line Items] Number of consolidated claims settled Loss Contingency, Claims Settled, Number Settlement charge Litigation Settlement, Expense Litigation settlement, amount awarded to other party Litigation Settlement, Amount Awarded to Other Party Amount of damages claimed Loss Contingency, Damages Sought, Value Potential acquisition-related contingent consideration, low end of range Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low Potential acquisition-related contingent consideration, high end of range Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High Remaining period over which potential acquisition-related contingent consideration would be payable Business Combination, Contingent Consideration Remaining Payment Period Business Combination, Contingent Consideration Remaining Payment Period Accounts Receivable, net Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Schedule of Accounts Receivable, Net Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Disposal Group Name [Axis] Disposal Group Name [Axis] Disposal Group Name [Domain] Disposal Group Name [Domain] Disposal Of Foreign Subsidiaries Disposal Of Foreign Subsidiaries [Member] Disposal Of Foreign Subsidiaries [Member] Products and Systems Products and Systems [Member] Products and Systems Disposal Group Classification [Axis] Disposal Group Classification [Axis] Disposal Group Classification [Domain] Disposal Group Classification [Domain] Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations [Member] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Number of subsidiaries classified as held for sale Disposal Group, Number of Subsidiaries Classified as Held-for-sale Disposal Group, Number of Subsidiaries Classified as Held-for-sale Percentage of consolidated revenues of subsidiary held for sale Disposal Group, Including Discontinued Operation, Liabilities, Percentage Of Consolidated Revenues Disposal Group, Including Discontinued Operation, Liabilities, Percentage Of Consolidated Revenues Income from operations of subsidiary held for sale Disposal Group, Including Discontinued Operation, Operating Income (Loss) Percentage of consolidated assets of subsidiary held for sale Disposal Group, Including Discontinued Operation, Assets, Percentage Of Consolidated Assets Disposal Group, Including Discontinued Operation, Assets, Percentage Of Consolidated Assets Percentage of liabilities of subsidiary held for sale Disposal Group, Including Discontinued Operation, Liabilities, Percentage Of Consolidated Liabilities Disposal Group, Including Discontinued Operation, Liabilities, Percentage Of Consolidated Liabilities Description of Business and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block] Schedule of Accrued Expenses and Other Current Liabilities Schedule of Accrued Liabilities Deferred Revenue and Contingent Consideration Liabilities Current [Table Text Block] Tabular disclosure of (a) other payables; (b) accrued liabilities; (c) deferred revenue; and (d) the fair value of contingent consideration liabilities, due within one year or within the normal operating cycle if longer. Intangible Assets, Net (Excluding Goodwill) [Abstract] Amortization expense Amortization of Intangible Assets Property, Plant and Equipment [Abstract] Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Land Land [Member] Buildings and improvements Building and Building Improvements [Member] Office furniture and equipment Office Furniture and Equipment [Member] Furniture and equipment commonly used in offices and stores that have no permanent connection to the structure of a building or utilities. Machinery and equipment Machinery and Equipment [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Property, Plant and Equipment, net Property, Plant and Equipment [Line Items] Useful Life (Years) Property, Plant and Equipment, Useful Life Property, plant and equipment, gross Property, Plant and Equipment, Gross Accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Property, plant and equipment, net Depreciation expense Depreciation Income Statement [Abstract] Revenue Cost of revenue Cost of Goods Sold, Excluding Depreciation, Depletion, and Amortization Depreciation Cost of Goods Sold, Depreciation Gross profit Gross Profit Selling, general and administrative expenses Selling, General and Administrative Expense Research and engineering Research and Development Expense Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Acquisition-related expense (benefit), net Income from operations Operating Income (Loss) Interest expense Interest Expense and Amortization of Deferred Charges The cost of borrowed funds accounted for as interest that was charged against earnings during the period and the amount of amortization of deferred charges applied against earnings during the period. Income before provision for income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Provision for income taxes Income Tax Expense (Benefit) Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Less: net income attributable to non-controlling interests, net of taxes Net Income (Loss) Attributable to Noncontrolling Interest Net income attributable to Mistras Group, Inc. Net Income (Loss) Attributable to Parent Earnings per common share: Basic (in dollars per share) Income (Loss) from Continuing Operations, Per Basic Share Diluted (in dollars per share) Income (Loss) from Continuing Operations, Per Diluted Share Weighted average common shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Accrued salaries, wages and related employee benefits Accrued Salaries Wages and Employee Related Benefits Current Carrying value as of the balance sheet date of the obligations incurred through that date and payable for salaries, wages, and related employee benefit. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle, if longer). Contingent consideration, current portion Business Combination, Contingent Consideration, Liability, Current Accrued workers’ compensation and health benefits Accrued Workers Compensation and Health Benefits Current Carrying value as of the balance sheet date of obligations and payables pertaining to workers compensation and health benefits. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle, if longer). Deferred revenue Deferred Revenue, Current Legal settlement accrual Loss Contingency, Accrual, Current Other accrued expenses Other Accrued Liabilities, Current Total accrued expenses and other liabilities Schedule of Disaggregated Revenues by Industry and Key Geographic Location Disaggregation of Revenue [Table Text Block] Statement of Cash Flows [Abstract] Cash flows from operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Net income Adjustments to reconcile net income to net cash provided by operating activities Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Depreciation, Depletion and Amortization Deferred income taxes Deferred Income Tax Noncash Expense (Benefit) The noncash component of income tax expense for the period representing the increase (decrease) in the entity's deferred tax assets and liabilities pertaining to continuing operations. Share-based compensation expense Share-based Compensation Bad debt provision for unexpected customer bankruptcy Provision for Doubtful Accounts Fair value adjustments to contingent consideration Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Liabilities Other Other Noncash Income (Expense) Changes in operating assets and liabilities, net of effect of acquisitions Increase (Decrease) in Operating Capital [Abstract] Accounts receivable Increase (Decrease) in Accounts Receivable Inventories Increase (Decrease) in Inventories Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Accounts payable Increase (Decrease) in Accounts Payable, Trade Accrued expenses and other liabilities Increase (Decrease) in Other Accrued Liabilities and Deferred Liabilities The increase (decrease) during the reporting period in other expenses incurred but not yet paid and the change during the period in carrying value for all deferred liabilities due within one year or operating cycle. Income taxes payable Increase (Decrease) in Income Taxes Payable Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Purchase of property, plant and equipment Payments to Acquire Property, Plant, and Equipment Purchase of intangible assets Payments to Acquire Intangible Assets and Software The cash outflow to acquire assets without physical form usually arising from contractual or other legal rights, excluding goodwill. In addition, the cash outflow associated with the development, modification or acquisition of software programs or applications for internal use (that is, not to be sold, leased or otherwise marketed to others) that qualify for capitalization. Acquisition of businesses, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Proceeds from sale of equipment Proceeds from Sale of Property, Plant, and Equipment Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Repayment of capital lease obligations Repayments of Long-term Capital Lease Obligations Proceeds from borrowings of long-term debt Proceeds from Issuance of Long-term Debt Repayment of long-term debt Repayments of Long-term Debt Proceeds from revolver Proceeds from Lines of Credit Repayment of revolver Repayments of Lines of Credit Payment of contingent consideration for business acquisitions Payments of Contingent Consideration for Business Acquisitions The cash outflow associated with the consideration paid on the achievement of specific performance metrics in connection with acquisition of business during the period. Purchases of treasury stock Payments for Repurchase of Common Stock Taxes paid related to net share settlement of share-based awards Payments Related to Tax Withholding for Share-based Compensation Proceeds from exercise of stock options Proceeds from Stock Options Exercised Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Effect of exchange rate changes on cash and cash equivalents Effect of Exchange Rate on Cash and Cash Equivalents, Continuing Operations Net change in cash and cash equivalents Net Cash Provided by (Used in) Continuing Operations Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Supplemental disclosure of cash paid Supplemental Cash Flow Information [Abstract] Interest Interest Paid Income taxes Income Taxes Paid Noncash investing and financing Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Equipment acquired through capital lease obligations Capital Lease Obligations Incurred Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Operating segments Operating Segments [Member] Corp/Elim Corporate And Eliminations [Member] Corporate And Eliminations International International [Member] Represents International, a business segment of the entity. Products Oil & Gas Oil & Gas [Member] Oil & Gas Aerospace & Defense Aerospace and Defense [Member] Aerospace and Defense Industrials Industrials [Member] Industrials Power generation & Transmission Power Generation and Transmission [Member] Power Generation and Transmission Other Process Industries Other Process Industries [Member] Other Process Industries Infrastructure, Research & Engineering Infrastructure, Research and Engineering [Member] Infrastructure, Research and Engineering Other Other Products and Services [Member] Other Products and Services Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Revenue Revenue from Contract with Customer, Excluding Assessed Tax Schedule of Computations of Basic and Diluted Earnings per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Fair Value Disclosures [Abstract] Schedule of Changes in Fair Value of Level 3 Contingent Consideration Fair Value, Liabilities Measured on Recurring Basis [Table Text Block] Basic earnings per share: Earnings Per Share, Basic [Abstract] Numerator: Net Income (Loss) Attributable to Parent [Abstract] Net income attributable to Mistras Group, Inc. Denominator: Weighted Average Number of Shares Outstanding, Basic [Abstract] Weighted average common shares outstanding (in shares) Basic earnings (loss) per share (in dollars per share) Diluted earnings per share: Earnings Per Share, Diluted [Abstract] Denominator: Dilutive effect of stock options outstanding (in shares) Incremental Common Shares Attributable to Stock Options Outstanding Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of stock options outstanding. Dilutive effect of restricted stock units outstanding (in shares) Incremental Common Shares Attributable to Restricted Stock Units Outstanding Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of restricted stock units outstanding. Weighted average common shares outstanding, diluted (in shares) Diluted earnings (loss) per share (in dollars per share) Number of operating segments Number of Operating Segments Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Corporate and eliminations Financial information by segment Segment Reporting Information [Line Items] Gross profit Income (loss) from operations Total assets Acquisitions Business Combination Disclosure [Text Block] Schedule of Property, plant and equipment Property, Plant and Equipment [Table Text Block] Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized (in shares) Common Stock, Shares Authorized Common stock, shares issued (in shares) Common Stock, Shares, Issued Goodwill Goodwill Disclosure [Text Block] Equity [Abstract] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Share Repurchase Program [Domain] Share Repurchase Program [Domain] Stock Repurchase Plan Stock Repurchase Plan [Member] Stock Repurchase Plan Chairman and CEO Board of Directors Chairman and Chief Executive Officer [Member] Board of Directors Chairman and Chief Executive Officer Class of Stock [Line Items] Class of Stock [Line Items] Stock repurchase plan, amount approved Stock Repurchase Program, Authorized Amount Stock repurchase plan, amount approved (in shares) Stock Repurchase Program, Number of Shares Authorized to be Repurchased Stock repurchase plan, amount approved each month from CEO Stock Repurchase Program, Authorized Amount Per Month Stock Repurchase Program, Authorized Amount Per Month Average daily price of common stock for the preceding month discount, percent Average Daily Price of Common Stock For Preceding Month Discount, Percent Average Daily Price of Common Stock For Preceding Month Discount, Percent Treasury stock repurchased (in shares) Treasury Stock, Shares, Acquired Treasury stock acquired, average price (in dollars per share) Treasury Stock Acquired, Average Cost Per Share Treasury stock acquired, aggregate cost Treasury Stock, Value, Acquired, Cost Method Stock repurchase plan, remaining amount approved Stock Repurchase Program, Remaining Authorized Repurchase Amount Property, Plant and Equipment, Net Property, Plant and Equipment Disclosure [Text Block] Repurchase of Common Stock Stockholders' Equity Note Disclosure [Text Block] Intangible Assets Intangible Assets Disclosure [Text Block] Segment Disclosure Segment Reporting Disclosure [Text Block] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 3 Fair Value, Inputs, Level 3 [Member] Fair value measurements Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Liabilities: Liabilities, Fair Value Disclosure [Abstract] Contingent Consideration Liability [Roll Forward] Contingent Consideration Liability [Roll Forward] Contingent Consideration Liability [Roll Forward] Beginning balance Acquisitions Business Combination, Contingent Consideration Arrangements, Acquisitions Business Combination, Contingent Consideration Arrangements, Acquisitions Payments Business Combination, Contingent Consideration Arrangements, Payments Business Combination, Contingent Consideration Arrangements, Payments Accretion of liability Business Combination, Contingent Consideration Arrangements, Contingent Consideration, Accretion of Liability Business Combination, Contingent Consideration, Accretion of Liability Revaluation Foreign currency translation Business Combination, Contingent Consideration Arrangements, Contingent Consideration, Foreign Currency Translation Adjustments Business Combination, Contingent Consideration Arrangements, Contingent Consideration, Foreign Currency Translation Adjustments Ending balance Concentration Risk [Table] Concentration Risk [Table] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Customer Concentration Risk Customer Concentration Risk [Member] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Revenues Sales Revenue, Net [Member] Concentration Risk [Line Items] Concentration Risk [Line Items] Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Adjustment to the impact to deferred tax assets previously recorded Tax Cuts and Jobs Act, Measurement Period Adjustment, Income Tax Expense (Benefit) Tax Cuts and Jobs Act, Measurement Period Adjustment, Income Tax Expense (Benefit) Concentration risk, percentage Concentration Risk, Percentage Stock Options Employee Stock Option [Member] Common Stock Options (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Outstanding at the beginning of the period: (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Exercised (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Expired or forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period Outstanding at the end of the period: (in shares) Weighted Average Exercise Price (in dollar per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Outstanding at the beginning of period: (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Granted (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Exercised (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Expired or forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price Outstanding at the end of period: (in dollars per share) Recognized share-based compensation expense (less than) Unrecognized compensation costs Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options Debt Disclosure [Abstract] Schedule of Long-Term Debt Schedule of Long-term Debt Instruments [Table Text Block] Statement of Comprehensive Income [Abstract] Other comprehensive income: Other Comprehensive Income (Loss), Net of Tax [Abstract] Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Less: comprehensive income attributable to non-controlling interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Comprehensive income attributable to Mistras Group, Inc. Comprehensive Income (Loss), Net of Tax, Attributable to Parent Revenue remaining performance obligation, expected timing of satisfaction period Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Revenue recognized that was included in contract liability balance at the beginning of the year Contract with Customer, Liability, Revenue Recognized Revenue, practical expedien, incremental cost of obtaining a contract, maximum period Revenue, Practical Expedient, Incremental Cost of Obtaining Contract, Maximum Period Revenue, Practical Expedient, Incremental Cost of Obtaining Contract, Maximum Period Schedule of Gross Amount, Accumulated Amortization and Net Carrying Amount of Intangibles Schedule of Finite-Lived Intangible Assets [Table Text Block] Performance Restricted Stock (Units) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Outstanding at beginning of period: (in shares) Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Performance condition adjustments (in shares) Released (in shares) Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Outstanding at end of period: (in shares) Weighted Average Grant-Date Fair Value (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Outstanding at the beginning of period: (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Granted (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Performance condition adjustments (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Adjustments in Period, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Adjustments in Period, Weighted Average Grant Date Fair Value Released (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Outstanding at end of period: (in dollars per share) Restricted Stock Units Awards (Units) Schedule of Consolidated Financial Information by Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Revenues by Geographic Areas Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area [Table Text Block] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Goodwill [Line Items] Goodwill [Line Items] Goodwill [Roll Forward] Goodwill [Roll Forward] Balance at December 31, 2017 Goodwill acquired during the period Goodwill, Acquired During Period Adjustments to preliminary purchase price allocations Goodwill, Purchase Accounting Adjustments Foreign currency translation Goodwill, Foreign Currency Translation Gain (Loss) Balance at March 31, 2018 Fair Value Measurements Fair Value Disclosures [Text Block] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Customer relationships Customer Relationships [Member] Software/Technology Computer Software, Intangible Asset [Member] Covenants not to compete Noncompete Agreements [Member] Other Other Intangible Assets [Member] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Useful Life (Years) Finite-Lived Intangible Asset, Useful Life Gross Amount Finite-Lived Intangible Assets, Gross Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Impairment Finite-Lived Intangible Assets, Impaired, Accumulated Impairment Loss Finite-Lived Intangible Assets, Impaired, Accumulated Impairment Loss Net Carrying Amount Goodwill cumulative impairment loss Goodwill, Impaired, Accumulated Impairment Loss Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Senior credit facility Revolving Credit Facility [Member] Notes payable Notes Payable, Other Payables [Member] Other Other Long Term Debt [Member] Represents details pertaining to other long-term debt of the entity. Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] LIBOR London Interbank Offered Rate (LIBOR) [Member] Base rate Base Rate [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Senior Credit Facility Line of Credit Facility [Abstract] Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Line of credit facility, higher borrowing capacity option Line Of Credit Facility, Accordion Feature, Higher Borrowing Capacity Option Line Of Credit Facility, Accordion Feature, Higher Borrowing Capacity Option Maximum borrowing capacity in non-U.S. Dollar currencies Line of Credit Facility Maximum Borrowing Capacity in Non US Currencies Represents the maximum borrowing capacity in non-U.S. dollar currencies under the revolving credit facility. Maximum amount available for the issuance of letters of credit Line of Credit Facility Maximum Borrowing Capacity Available for Issuance of Letters of Credit Represents the maximum amount of borrowing capacity under the revolving credit facility that is available for the issuance of letters of credit. Outstanding borrowings Long-term Line of Credit Outstanding letters of credit Letters of Credit Outstanding, Amount Reference rate, description Debt Instrument, Description of Variable Rate Basis Margin (as a percent) Debt Instrument, Basis Spread on Variable Rate Amount of non-recurring charges used as threshold used for calculation of funded debt leverage ratio Debt Instrument, Non-recurring Charges Threshold Used For Calculation of Funded Debt Leverage Ratio Debt Instrument, Non-recurring Charges Threshold Used For Calculation of Funded Debt Leverage Ratio Number of consecutive fiscal quarters used for calculating funded debt leverage ratio Debt Instrument, Number of Fiscal Quarters Used for Calculation of Funded Debt Leverage Ratio Represents the number of consecutive fiscal quarters immediately preceding the date of determination of the Funded Debt Leverage Ratio. Funded debt leverage ratio at which the entity will have the benefit of lowest interest margin (less than or equal to) Debt Instrument, Covenant Funded Leverage Ratio Considered for Lower Interest Rate Margin Represents the Funded Debt Leverage Ratio at which the entity will have the benefit of lower interest rate margin. Funded debt leverage ratio at which the entity will bear the maximum interest rate margin (greater than) Debt Instrument, Covenant Funded Leverage Ratio Considered for Maximum Interest Rate Margin Represents the Funded Debt Leverage Ratio at which the entity will have the maximum interest rate margin. Additional interest rate margin if funded debt leverage ratio exceeds threshold (as a percent) Debt Instrument, Additional Interest Rate Due to Funded Debt Leverage Ratio Exceeding Specified Threshold The percentage points added to the reference rate due to the Funded Debt Leverage Ratio, which is used to compute the variable rate on the debt instrument, exceeding a specified threshold. Funded debt leverage ratio for additional interest payment (less than) Debt Instrument, Covenant Funded Debt Leverage Ratio for Additional Interest Payment Represents the Funded Debt Leverage Ratio on which the entity will bear an additional interest on debt. Interest coverage ratio (greater than) Debt Instrument, Covenant Interest Coverage Ratio Represents the Interest Coverage Ratio required under the terms of the covenants. Preceding period used for calculating Interest Coverage Ratio Debt Instrument, Preceding Period Used for Calculation of Interest Coverage Ratio Represents the preceding period used for determination of the Interest Coverage Ratio. Temporary increase in funded debt leverage ratio Debt Instrument, Covenant Temporarily Increase in Funded Debt Leverage Ratio due to Business Acquisitions Debt Instrument, Covenant Temporarily Increase in Funded Debt Leverage Ratio due to Business Acquisitions Number of fiscal quarters to temporary increase funded debt leverage ratio Debt Instrument, Number of Fiscal Quarters To Temporarily Increase Funded Debt Leverage Ratio due to Business Acquisitions Debt Instrument, Number of Fiscal Quarters To Temporarily Increase Funded Debt Leverage Ratio due to Business Acquisitions Notes Payable and Other Notes and Loans Payable, Current and Noncurrent [Abstract] Maturity term from the date of acquisition Debt Instrument, Term Interest rate (as a percent) Debt Instrument, Interest Rate, Stated Percentage Debt outstanding Long-term Debt Debt monthly periodic payments Debt Instrument, Periodic Payment Total debt Less: Current portion Long-Term Debt Long-term Debt [Text Block] Allowance for doubtful accounts Allowance for Doubtful Accounts Receivable, Current Accounts receivable, net