v3.19.1
Document and Entity Information - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Mar. 12, 2019
Jun. 30, 2018
Document and Entity Information      
Entity Registrant Name Mistras Group, Inc.    
Entity Central Index Key 0001436126    
Document Type 10-K    
Document Period End Date Dec. 31, 2018    
Amendment Flag false    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Accelerated Filer    
Entity Shell Company false    
Entity Public Float     $ 327.2
Entity Common Stock, Shares Outstanding   28,562,708  
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY