Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating expenses
Selling, general and administrative	$ 19,774	$ 10,627	$ 51,402	$ 29,814
Research and development	12,408	12,688	33,977	38,301
Total operating expenses	32,182	23,315	85,379	68,115
Loss from operations	(32,182)	(23,315)	(85,379)	(68,115)
Other income (expense), net	(141)	(460)	(1,071)	(1,490)
Net loss before income taxes	(32,323)	(23,775)	(86,450)	(69,605)
Income tax expense	49	39	142	132
Net loss	$ (32,372)	$ (23,814)	$ (86,592)	$ (69,737)
Net loss per share attributable to common stockholders—basic and diluted (in dollars per share)	$ (0.89)	$ (0.81)	$ (2.48)	$ (2.52)
Weighted average number of common shares outstanding—basic and diluted (in shares)	36,210,329	29,380,453	34,932,551	27,632,090
Net loss	$ (32,372)	$ (23,814)	$ (86,592)	$ (69,737)
Unrealized (loss) gain on available-for-sale investments	(17)	(3)	(30)	166
Comprehensive loss	$ (32,389)	$ (23,817)	$ (86,622)	$ (69,571)