v3.3.1.900
Document and Entity Information Document - USD ($)
12 Months Ended
Dec. 31, 2015
Feb. 17, 2016
Jun. 30, 2015
Entity Information [Line Items]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2015    
Document Fiscal Year Focus 2015    
Document Fiscal Period Focus FY    
Trading Symbol MANT    
Entity Registrant Name MANTECH INTERNATIONAL CORP    
Entity Central Index Key 0000892537    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Large Accelerated Filer    
Entity Public Float     $ 703,653,216
Class A Common Stock [Member]      
Entity Information [Line Items]      
Common Stock, Shares Outstanding   24,494,472  
Class B Common Stock [Member]      
Entity Information [Line Items]      
Common Stock, Shares Outstanding   13,191,845