| Cover | Jun. 15, 2021 | May 13, 2021 |
| Cover [Abstract] | ||
| Document Type | 8-K | |
| Document Period End Date | Jun. 15, 2021 | |
| Entity Registrant Name | MACROGENICS, INC. | |
| Entity Incorporation, State or Country Code | DE | |
| Entity File Number | 001-36112 | |
| Entity Tax Identification Number | 06-1591613 | |
| Entity Address, Address Line One | 9704 Medical Center Drive | |
| Entity Address, City or Town | Rockville, | |
| Entity Address, State or Province | MD | |
| Entity Address, Postal Zip Code | 20850 | |
| City Area Code | 301 | |
| Local Phone Number | 251-5172 | |
| Title of 12(b) Security | Common Stock, par value $0.01 per share | |
| Trading Symbol | MGNX | |
| 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 | |
| Entity Central Index Key | 0001125345 | |
| Amendment Flag | false |
