SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)
Product sales	$ 123,675	$ 110,303	$ 116,517	$ 104,571	$ 111,059	$ 104,726	$ 94,295	$ 31,670	$ 455,066	$ 341,750	$ 114,219
Total revenues	123,911	110,524	116,682	104,780	111,172	104,856	94,504	32,203	455,897	342,735	390,363
Gross margin on product sales	101,018	90,060	95,552	81,022	90,052	83,812	71,430	28,558
Income (loss) from operations	17,904	1,258	9,661	(4,314)	(26,572)	3,235	(17,214)	(9,849)	24,509	(50,400)	236,814
Net income (loss)	$ (44,368)	$ (12,894)	$ (10,541)	$ (20,917)	$ (30,667)	$ (11,785)	$ (21,653)	$ (11,633)	$ (88,720)	$ (75,738)	$ 131,762
Basic net income (loss) per share (in dollars per share)	$ (0.72)	$ (0.21)	$ (0.17)	$ (0.34)	$ (0.51)	$ (0.20)	$ (0.36)	$ (0.20)	$ (1.45)	$ (1.26)	$ 2.26
Diluted net income (loss) per share (in dollars per share)	$ (0.72)	$ (0.21)	$ (0.17)	$ (0.34)	$ (0.51)	$ (0.20)	$ (0.36)	$ (0.20)	$ (1.45)	$ (1.26)	$ 2.05