Revenue Recognition - Adoption of Topic 606 (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
	Jan. 01, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation Of Revenue [Line Items]
Inventory		$ 24,968				$ 39,032				$ 24,968	$ 39,032	$ 10,108
Other accrued liabilities		36,535				32,715				36,535	32,715	17,175
Deferred revenue												2,763
Accumulated deficit		(1,165,470)				(960,721)				(1,165,470)	(960,721)	(783,455)
Net product sales		35,083	$ 42,624	$ 36,659	$ 31,602	28,844	$ 19,786	$ 17,277	$ 11,567	145,968	77,474	30,767
Cost of product sales		15,874	17,195	13,588	14,962	11,572	7,576	5,231	3,133	61,619	27,512	4,588
Loss from operations		(59,362)	(34,853)	(51,779)	(64,700)	(51,314)	(41,780)	(38,853)	(51,990)	(210,694)	(183,937)	(194,558)
Net loss		$ (57,920)	$ (33,595)	$ (50,222)	$ (63,012)	$ (49,559)	$ (38,346)	$ (38,670)	$ (52,265)	$ (204,749)	$ (178,840)	$ (197,484)
Basic and diluted net loss per share		$ (0.65)	$ (0.42)	$ (0.63)	$ (0.80)	$ (0.63)	$ (0.49)	$ (0.54)	$ (0.81)	$ (2.50)	$ (2.44)	$ (3.65)
Adjustments to reconcile net loss to net cash used for operating activities:
Inventory										$ 14,064	$ (29,122)	$ (4,768)
Other accrued liabilities										$ 4,558	14,941	11,482
Deferred revenue												$ 1,664
Accounting Standards Update 2014-09
Disaggregation Of Revenue [Line Items]
Inventory	$ 9,910
Other accrued liabilities	18,166
Accumulated deficit	(781,881)
Cost of product sales	200
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Disaggregation Of Revenue [Line Items]
Inventory	(198)					$ 2,181					2,181
Other accrued liabilities	991					(7,195)					(7,195)
Deferred revenue	(2,763)					14,010					14,010
Accumulated deficit	$ 1,574					(4,634)					(4,634)
Net product sales											(5,043)
Cost of product sales											(1,983)
Loss from operations											(3,060)
Net loss											$ (3,060)
Basic and diluted net loss per share											$ 0.05
Adjustments to reconcile net loss to net cash used for operating activities:
Inventory											$ (1,983)
Other accrued liabilities											(6,204)
Deferred revenue											11,247
Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation Of Revenue [Line Items]
Inventory						41,213					41,213
Other accrued liabilities						25,520					25,520
Deferred revenue						14,010					14,010
Accumulated deficit						$ (965,355)					(965,355)
Net product sales											72,431
Cost of product sales											25,529
Loss from operations											(186,997)
Net loss											$ (181,900)
Basic and diluted net loss per share											$ (2.49)
Adjustments to reconcile net loss to net cash used for operating activities:
Inventory											$ (31,105)
Other accrued liabilities											8,737
Deferred revenue											$ 11,247