Consolidated Statements of Operations - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net revenues	$ 138,438,000	$ 13,574,000	$ 0
Cost of product sales	77,220,000	5,971,000	0
Operating expenses:
Selling, general and administrative	96,472,000	29,525,000	16,222,000
Research and development	49,008,000	14,784,000	9,790,000
Restructuring charges	2,536,000	0	0
Termination fee	0	0	(2,667,000)
Total operating expenses	148,016,000	44,309,000	23,345,000
Loss from operations	(86,798,000)	(36,706,000)	(23,345,000)
Interest (expense) income, net	(39,037,000)	(2,960,000)	277,000
Fair value loss on investment	0	(10,740,000)	0
Other (expense) income, net	(292,000)	(1,999,000)	81,000
Loss before provision for income taxes	(126,127,000)	(52,405,000)	(22,987,000)
Provision for income taxes	(583,000)	(465,000)	(22,000)
Net loss	$ (126,710,000)	$ (52,870,000)	$ (23,009,000)
Net loss per common share—basic and diluted (in dollars per share)	$ (6.81)	$ (4.69)	$ (2.20)
Weighted-average shares outstanding—basic and diluted (in shares)	18,616	11,284	10,434