| Document and Entity Information | Jul. 30, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001300699 |
| Document Type | 8-K |
| Document Period End Date | Jul. 30, 2021 |
| Entity Registrant Name | ATHENEX, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-38112 |
| Entity Tax Identification Number | 43-1985966 |
| Entity Address, Address Line One | 1001 Main Street |
| Entity Address, Address Line Two | Suite 600 |
| Entity Address, City or Town | Buffalo |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 14203 |
| City Area Code | (716) |
| Local Phone Number | 427-2950 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $0.001 per share |
| Trading Symbol | ATNX |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
