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	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential dilutive common shares	9,928,066	10,573,173	11,763,905
Stock Options and Other Common Stock Equivalents
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential dilutive common shares	9,534,658	9,624,689	10,601,684
Unvested Restricted Common Shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential dilutive common shares	393,408	948,484	1,162,221