| Cover | Jan. 05, 2023 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Jan. 05, 2023 |
| Entity Registrant Name | ZAI LAB LIMITED |
| Entity Incorporation, State or Country Code | E9 |
| Entity File Number | 001-38205 |
| Entity Tax Identification Number | 98-1144595 |
| Entity Address, Address Line One | 4560 Jinke Road |
| Entity Address, Address Line Two | Bldg. 1, Fourth Floor, Pudong |
| Entity Address, City or Town | Shanghai |
| Entity Address, Country | CN |
| Entity Address, Postal Zip Code | 201210 |
| City Area Code | 86 21 |
| Local Phone Number | 6163 2588 |
| 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 | 0001704292 |
| ADR | |
| Document Information [Line Items] | |
| Title of 12(b) Security | American Depositary Shares, each representing 10 Ordinary Shares, par value $0.000006 per share |
| Trading Symbol | ZLAB |
| Security Exchange Name | NASDAQ |
| Common Stock | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Ordinary Shares, par value $0.000006 per share* |
| Trading Symbol | 9688 |
