Basis of Presentation and Significant Accounting Policies - New Accounting Pronouncements - Recently Adopted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended					6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2015	Jun. 30, 2017	Jun. 30, 2016
Revised Statements of Operations and Comprehensive Loss
Product revenue, net	$ 28,829			$ 1,242		$ 30,968	$ 1,518
License revenue	635			34,568		1,569	34,592
Cost of sales - product	3,620			234		4,064	313
Loss from operations	(148,514)			(55,243)		(281,759)	(142,344)
Net loss	$ (152,059)			$ (59,154)		$ (288,784)	$ (150,134)
Net loss per share applicable to common stockholders - basic and diluted (in dollars per share)	$ (2.82)			$ (1.29)		$ (5.36)	$ (3.46)
Revised Statement of Financial Position
Accounts receivable	$ 23,149	$ 6,195				$ 23,149
Other current assets	23,045	10,515				23,045
Accrued expenses	99,589	68,700				99,589
Deferred revenue, current	95	95				95
Deferred revenue, non-current	258	305				258
Customer deposit		15,000
Accumulated deficit	(1,262,545)	(973,761)				(1,262,545)
Revised Statement of Cash Flow
Net loss	(152,059)			$ (59,154)		(288,784)	$ (150,134)
Adjustments to reconcile net loss to net cash used in operating activities:
Accounts receivable						(16,954)	1,152
Other assets						(10,950)	(2,112)
Accrued expenses						19,746	6,506
Deferred revenues						(46)	417
Cash and cash equivalents at beginning of period			$ 320,204			785,877	230,146
Cash and cash equivalents at end of period	507,941	785,877		320,204		507,941	320,204
Collaborative Arrangement
Revised Statements of Operations and Comprehensive Loss
License revenue			14,800
License Agreement
Revised Statements of Operations and Comprehensive Loss
License revenue					$ 1,900
Zai Lab
Revised Statements of Operations and Comprehensive Loss
License revenue	0					$ 0
Zai Lab | Collaborative Arrangement
Impact of Adoption
Previously recognized revenue	0
Impact of potential future payments on transaction price	$ 0
ASU No. 2014-09
Revised Statements of Operations and Comprehensive Loss
Product revenue, net				1,242			1,518
License revenue				34,568			34,592
Cost of sales - product				234			313
Loss from operations				(55,243)			(142,344)
Net loss				$ (59,154)			$ (150,134)
Net loss per share applicable to common stockholders - basic and diluted (in dollars per share)				$ (1.29)			$ (3.46)
Revised Statement of Financial Position
Accounts receivable		6,195
Other current assets		10,515
Accrued expenses		68,700
Deferred revenue, current		95
Deferred revenue, non-current		305
Accumulated deficit		(973,761)
Revised Statement of Cash Flow
Net loss				$ (59,154)			$ (150,134)
Adjustments to reconcile net loss to net cash used in operating activities:
Accounts receivable							1,152
Other assets							(2,112)
Accrued expenses							6,506
Deferred revenues							417
Cash and cash equivalents at beginning of period			320,204				230,146
Cash and cash equivalents at end of period				320,204			320,204
Effect of change | ASU No. 2014-09
Revised Statements of Operations and Comprehensive Loss
Product revenue, net				(194)			(91)
License revenue				(557)			(667)
Cost of sales - product				(4)			(1)
Loss from operations				(747)			(757)
Net loss				$ (747)			$ (757)
Net loss per share applicable to common stockholders - basic and diluted (in dollars per share)				$ (0.01)			$ (0.02)
Revised Statement of Financial Position
Accounts receivable		852
Other current assets		1,596
Accrued expenses		429
Deferred revenue, current		(193)
Deferred revenue, non-current		305
Customer deposit		(15,000)
Accumulated deficit		16,907
Revised Statement of Cash Flow
Net loss				$ (747)			$ (757)
Adjustments to reconcile net loss to net cash used in operating activities:
Accounts receivable							983
Other assets							184
Accrued expenses							85
Deferred revenues							(495)
As originally reported under Topic 605 | ASU No. 2014-09
Revised Statements of Operations and Comprehensive Loss
Product revenue, net				1,436			1,609
License revenue				35,125			35,259
Cost of sales - product				238			314
Loss from operations				(54,496)			(141,587)
Net loss				$ (58,407)			$ (149,377)
Net loss per share applicable to common stockholders - basic and diluted (in dollars per share)				$ (1.28)			$ (3.44)
Revised Statement of Financial Position
Accounts receivable		5,343
Other current assets		8,919
Accrued expenses		68,271
Deferred revenue, current		288
Customer deposit		15,000
Accumulated deficit		$ (990,668)
Revised Statement of Cash Flow
Net loss				$ (58,407)			$ (149,377)
Adjustments to reconcile net loss to net cash used in operating activities:
Accounts receivable							169
Other assets							(2,296)
Accrued expenses							6,421
Deferred revenues							912
Cash and cash equivalents at beginning of period			$ 320,204				230,146
Cash and cash equivalents at end of period				$ 320,204			$ 320,204