CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Net product sales	$ 41,337	$ 38,800	$ 79,769	$ 72,420
Operating expenses:
Cost of goods sold	1,178	797	2,791	1,506
Research and development	34,460	19,482	59,096	40,342
Selling, general and administrative	25,100	28,835	51,568	51,950
Change in fair value of contingent consideration	2,159	3,284	5,786	6,628
Total operating expenses	62,897	52,398	119,241	100,426
Operating loss	(21,560)	(13,598)	(39,472)	(28,006)
Other income (expenses), net:
Other income (expense), net	(403)	382	(282)	508
Interest expense, net	(199)	(658)	(557)	(790)
Change in fair value of derivative instruments	0	(1,280)	0	(20)
Total other expense, net	(602)	(1,556)	(839)	(302)
Loss before provision for income taxes	(22,162)	(15,154)	(40,311)	(28,308)
Income tax benefit (expense)	(167)	1,925	(396)	3,989
Net loss	$ (22,329)	$ (13,229)	$ (40,707)	$ (24,319)
Net Income Loss Per Common Share [Abstract]
Basic and Diluted (in dollars/share)	$ (0.56)	$ (0.34)	$ (1.03)	$ (0.63)
Weighted Average Common Shares Outstanding [Abstract]
Basic and Diluted (in shares)	40,061,045	39,041,145	39,641,334	38,545,982
Comprehensive loss:
Net loss	$ (22,329)	$ (13,229)	$ (40,707)	$ (24,319)
Foreign currency translation	2	(183)	24	(259)
Unrealized gain (loss) on marketable securities	375	27	(161)	173
Comprehensive loss	$ (21,952)	$ (13,385)	$ (40,844)	$ (24,405)