CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Net product sales	$ 51,139	$ 44,373	$ 147,338	$ 128,651
Operating expenses:
Cost of goods sold	1,189	1,513	4,054	3,509
Research and development	32,349	33,220	93,387	104,597
Selling, general and administrative	31,951	29,779	100,061	101,418
Changes in the fair value of contingent consideration	5,085	(702)	7,448	5,820
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)
Impairment of long-term investment	0	15,000	0	15,000
Total operating expenses	70,574	78,810	204,950	237,844
Operating loss	(19,435)	(34,437)	(57,612)	(109,193)
Other income (expenses), net:
Other income (expense), net	553	(496)	788	(673)
Interest income	1,123	2,467	4,414	7,875
Interest expense	(4,767)	(4,547)	(14,287)	(14,230)
Total other expense, net	(3,091)	(2,576)	(9,085)	(7,028)
Loss before income taxes	(22,526)	(37,013)	(66,697)	(116,221)
Income tax (expense) benefit	(23)	523	18,888	53
Net income (loss)	$ (22,549)	$ (36,490)	$ (47,809)	$ (116,168)
Net income (loss) per common share, basic and diluted (in dollars per share)	$ (0.44)	$ (0.85)	$ (1.03)	$ (2.76)
Weighted average common shares outstanding, basic and diluted (in shares)	50,929,575	42,943,828	46,289,103	42,109,618
Comprehensive loss:
Net income (loss)	$ (22,549)	$ (36,490)	$ (47,809)	$ (116,168)
Foreign currency translation	(564)	315	(620)	342
Unrealized gain (loss) on debt securities	(480)	75	250	2,359
Comprehensive loss	$ (23,593)	$ (36,100)	$ (48,179)	$ (113,467)