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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential dilutive common shares	111,124,335	11,001,494	10,549,948	10,433,589
Stock Options and Other Common Stock Equivalents
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential dilutive common shares	111,119,444	10,736,494	10,397,140	9,989,045
Unvested Restricted Common Shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential dilutive common shares	4,891	265,000	152,808	444,544