QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Net product sales	$ 30,447	$ 28,005	$ 24,068	$ 17,372	$ 14,085	$ 8,348	$ 5,742	$ 28	$ 99,892	$ 28,203	$ 0
Total operating expenses	45,651	48,501	31,012	25,476	32,782	30,215	22,924	22,090	150,640	108,011	24,773
Operating loss	(15,204)	(20,496)	(6,944)	(8,104)	(18,697)	(21,867)	(17,182)	(22,062)	(50,748)	(79,808)	(24,773)
Total other income (expense), net	2,210	164,835	(18,568)	7,738	(10,330)	3,887	26,462	(53,609)	(296)	2,352	370
Income (loss) before provision for income taxes	(12,994)	144,339	(25,512)	(366)	(29,027)	(17,980)	9,280	(75,671)	105,467	(113,398)	(34,549)
Income tax benefit(provision)	10,525	(38,761)	(15)	40,021	0	0	2,525	(65)	11,770	2,460	(76)
Net income (loss)	$ (2,469)	$ 105,578	$ (25,527)	$ 39,655	$ (29,027)	$ (17,980)	$ 11,805	$ (75,736)	$ 117,237	$ (110,938)	$ (34,625)
Per Share Data:
Net loss per common share, basic (in dollars per shares)	$ (0.07)	$ 2.95	$ (0.73)	$ 1.46	$ (1.10)	$ (0.67)	$ 0.46	$ (3.25)	$ 3.49	$ (4.43)	$ (2.44)
Net loss per common share, diluted (in dollars per shares)	$ (0.14)	$ 1.78	$ (0.73)	$ 1.32	$ (1.10)	$ (0.84)	$ (0.77)	$ (3.25)	$ 3.17	$ (4.43)	$ (2.44)