| Cover Page | Sep. 24, 2019 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Sep. 24, 2019 |
| Entity Registrant Name | ANAPTYSBIO, INC |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-37985 |
| Entity Tax Identification Number | 20-3828755 |
| Entity Address, Address Line One | 10421 Pacific Center Court |
| Entity Address, Address Line Two | Suite 200 |
| Entity Address, City or Town | San Diego |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92121 |
| City Area Code | 858 |
| Local Phone Number | 362-6295 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.001 per share |
| Trading Symbol | ANAB |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001370053 |
| Amendment Flag | false |
