Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
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
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 39,338	$ 4,208	$ 27,666	$ 2,780	$ 3,816	$ 3,258	$ 3,685	$ 3,232	$ 73,993	$ 13,991	$ 13,481
Total costs and expenses	64,919	53,131	48,802	43,585	40,622	33,320	33,591	30,872	210,438	138,405	123,464
Income (loss) from operations	(25,581)	(48,923)	(21,136)	(40,805)	(36,806)	(30,062)	(29,906)	(27,640)	(136,445)	(124,414)	(109,983)
Net loss	$ (23,575)	$ (45,369)	$ (17,862)	$ (38,053)	$ (34,734)	$ (28,979)	$ (28,938)	$ (26,219)	$ (124,858)	$ (118,871)	$ (108,454)
Net loss per share applicable to common stockholders-basic and diluted (in dollars per share)	$ (0.44)	$ (0.86)	$ (0.34)	$ (0.74)	$ (0.75)	$ (0.63)	$ (0.63)	$ (0.58)	$ (2.38)	$ (2.59)	$ (2.68)

Total costs of sales and operating expenses for the period.

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