Selected Quarterly Financial Data (Unaudited) (Details) - 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
Selected Quarterly Financial Information [Abstract]
Net revenue	$ 7,663	$ 13,469	$ 980	$ 0
Gross profit	6,889	13,016	875	0
Net loss	(71,017)	(57,843)	(68,438)	(56,939)	$ (52,720)	$ (46,186)	$ (43,435)	$ (40,463)	$ (254,237)	$ (182,804)	$ (101,526)
Net loss applicable to common stock	$ (71,017)	$ (57,843)	$ (68,438)	$ (56,939)	$ (52,720)	$ (46,186)	$ (43,435)	$ (40,463)	$ (254,237)	$ (182,804)	$ (101,526)
Net loss per share—basic and diluted (in dollars per share)	$ (1.59)	$ (1.31)	$ (1.58)	$ (1.32)	$ (1.22)	$ (1.07)	$ (1.01)	$ (0.94)	$ (5.80)	$ (4.24)	$ (2.56)
Weighted-average common shares outstanding—basic and diluted (in shares)	44,602,254	43,999,451	43,410,053	43,185,952	43,122,210	43,092,921	43,042,883	43,012,924	43,804,660	43,067,952	39,643,099