SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)
Product sales	$ 18,789	$ 16,278	$ 14,106	$ 9,129	$ 12,489	$ 9,684	$ 3,201	$ 2,109	$ 58,302	$ 27,483	$ 41,178
Total revenues	40,608	37,460	29,963	26,174	26,590	33,282	14,110	16,835	134,205	90,816	132,973
Gross margin on product sales	16,621	14,527	12,418	7,645	10,173	7,921	1,759	1,591
Income (loss) from operations	7,480	6,838	532	(5,533)	(3,891)	(1,541)	(15,983)	(8,938)	9,317	(30,353)	70,698
Net income (loss)	$ 41,801	$ 6,514	$ 478	$ (5,480)	$ (3,704)	$ (1,495)	$ (15,780)	$ (8,804)	$ 43,313	$ (29,781)	$ 70,726
Basic net income (loss) per share (in dollars per share)	$ 0.73	$ 0.11	$ 0.01	$ (0.10)	$ (0.07)	$ (0.03)	$ (0.28)	$ (0.16)	$ 0.76	$ (0.53)	$ 1.30
Diluted net income (loss) per share (in dollars per share)	$ 0.72	$ 0.11	$ 0.01	$ (0.10)	$ (0.07)	$ (0.03)	$ (0.28)	$ (0.16)	$ 0.75	$ (0.53)	$ 1.26