Net Loss per Share Attributable to Athenex, Inc. Common Stockholders - Schedule Outstanding Shares of Common Stock Equivalents Excluded from the Calculation of Diluted Net Loss Per Share (Detail) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential dilutive shares	13,921,691	11,452,475
Stock Options and Other Common Stock Equivalents
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential dilutive shares	13,899,191	11,347,475
Unvested Restricted Common Shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential dilutive shares	22,500	105,000