CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Net product sales	$ 48,430	$ 44,707	$ 96,199	$ 84,277
Operating expenses:
Cost of goods sold	1,494	979	2,864	1,996
Research and development	30,790	37,934	61,038	71,377
Selling, general and administrative	34,971	38,970	68,110	71,639
Changes in the fair value of contingent consideration	4,286	3,353	2,363	6,522
Write off of L-UDCA IPR&D intangible asset	0	0	0	25,500
Write off of L-UDCA contingent consideration	0	0	0	(18,000)
Total operating expenses	71,541	81,236	134,375	159,034
Operating loss	(23,111)	(36,529)	(38,176)	(74,757)
Other income (expenses), net:
Other income (expense), net	426	125	235	(177)
Interest income	1,316	2,589	3,291	5,408
Interest expense	(4,634)	(4,817)	(9,521)	(9,682)
Total other expense, net	(2,892)	(2,103)	(5,995)	(4,451)
Loss before income taxes	(26,003)	(38,632)	(44,171)	(79,208)
Income tax (expense) benefit	(65)	(69)	18,911	(470)
Net income (loss)	$ (26,068)	$ (38,701)	$ (25,260)	$ (79,678)
Net income (loss) per common share, basic and diluted (in dollars per share)	$ (0.58)	$ (0.92)	$ (0.57)	$ (1.91)
Weighted average common shares outstanding, basic and diluted (in shares)	44,763,843	41,957,860	43,943,370	41,685,599
Comprehensive loss:
Net income (loss)	$ (26,068)	$ (38,701)	$ (25,260)	$ (79,678)
Foreign currency translation	(247)	(91)	(56)	27
Unrealized gain on debt securities	3,146	815	729	2,284
Comprehensive loss	$ (23,169)	$ (37,977)	$ (24,587)	$ (77,367)