v3.8.0.1
Document and Entity Information Document - shares
3 Months Ended
Mar. 31, 2018
May 02, 2018
Entity Information [Line Items]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q1  
Trading Symbol MANT  
Entity Registrant Name MANTECH INTERNATIONAL CORP  
Entity Central Index Key 0000892537  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Class A common stock    
Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding   26,352,452
Class B common stock    
Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding   13,189,245