Selected Quarterly Financial Data (Unaudited) - Schedule of Quarterly Results of Operations (Unaudited) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Product sales	$ 14,128		$ 13,662		$ 4,416		$ 3,900		$ 4,851		$ 5,235		$ 4,820		$ 4,488		$ 36,106	$ 19,394	$ 12,816
License fees and consulting revenue	349		60		98		598		150		76		71		95		1,105	392	314
Grant revenue	396		272		81		83		112		305		302		46		832	765	814
Total revenue	14,873		13,994		4,595		4,581		5,113		5,616		5,193		4,629		38,043	20,551	13,944
Costs and operating expenses:
Cost of sales	10,064		8,082		4,137		2,839		5,326		5,416		4,834		4,142		25,122	19,718	13,153
Research and development expenses	20,848		11,944		17,597		26,408		27,181		18,052		8,645		6,746		76,797	60,624	24,463
Selling, general, and administrative expenses	12,317		10,364		13,632		9,799		10,262		6,790		4,567		4,337		46,112	25,956	27,036
Total costs and operating expenses	43,229		30,390		35,366		39,046		42,769		30,258		18,046		15,225		148,031	106,298	64,652
Operating loss	(28,356)		(16,396)		(30,771)		(34,465)		(37,656)		(24,642)		(12,853)		(10,596)		(109,988)	(85,747)	(50,708)
Net loss	(28,395)	[1]	(23,308)	[1]	(38,668)	[1]	(41,025)	[1]	(40,101)	[1]	(24,656)	[1]	(12,499)	[1]	(10,650)	[1]	(131,396)	(87,906)	(50,655)
Less: net loss attributable to non-controlling interests	(112)		(34)		(43)		(37)		(47)		(34)		(78)		(32)		(226)	(191)	(55)
Net loss attributable to Athenex, Inc.	$ (28,283)		$ (23,274)		$ (38,625)		$ (40,988)		$ (40,054)		$ (24,622)		$ (12,421)		$ (10,618)		$ (131,170)	$ (87,715)	$ (50,600)
Net loss per share attributable to Athenex, Inc. common stockholders, basic and diluted	$ (0.49)		$ (0.41)		$ (0.88)		$ (1.01)		$ (0.98)		$ (0.61)		$ (0.31)		$ (0.27)		$ (2.63)	$ (2.19)	$ (1.50)

[1] Results for the quarters ended September 30 and December 31, 2016 and March 31, June 30, and September 30, 2017 include interest expense and losses on derivative liabilities related to convertible notes.