| Document and Entity Information Document | Oct. 30, 2019 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Oct. 30, 2019 |
| Entity Registrant Name | ManTech International Corp |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 000-49604 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0000892537 |
