Cover Page Cover Page - shares	6 Months Ended
	Jun. 30, 2021	Aug. 02, 2021
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
Document Transition Report	false
Entity File Number	000-49604
Entity Registrant Name	ManTech International Corporation
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	22-1852179
Entity Address, Address Line One	2251 Corporate Park Drive
Entity Address, City or Town	Herndon
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	20171
City Area Code	703
Local Phone Number	218-6000
Title of 12(b) Security	Class A Common Stock
Trading Symbol	MANT
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Small Reporting Company	false
Emerging Growth Company	false
Entity Shell Company	false
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity Central Index Key	0000892537
Current Fiscal Year End Date	--12-31
Class A common stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		27,509,948
Class B common stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		13,176,695