Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Balances at Dec. 31, 2011	$ 1,321	$ 714	$ 250,885	$ 13	$ (250,291)
Balance, Shares at Dec. 31, 2011		71,463,676
Common stock issued under equity incentive and employee stock purchase plans, net of shares withheld for employee taxes, Amount	20,438	34	20,404
Common stock issued under equity incentive and employee stock purchase plans, net of shares withheld for employee taxes, Shares		3,311,263
Stock-based compensation expense	23,678		23,678
Equity component of Convertible Notes, net of issuance costs	69,335		69,335
Stock appreciation rights-reclassification from current liabilities to stockholders' equity	110		110
Change in comprehensive income	20			20
Net income (loss)	(41,257)				(41,257)
Balances at Dec. 31, 2012	73,645	748	364,412	33	(291,548)
Balance, Shares at Dec. 31, 2012		74,774,939
Common stock issued under equity incentive and employee stock purchase plans, net of shares withheld for employee taxes, Amount	8,870	10	8,860
Common stock issued under equity incentive and employee stock purchase plans, net of shares withheld for employee taxes, Shares		1,002,609
Common stock issued for warrant exercises, net of shares withheld for exercise price	0	0	0	0	0
Common stock issued for warrant exercises, net of shares withheld for exercise price, Shares		25,472
Stock-based compensation expense	37,078		37,078
Change in comprehensive income	(33)			(33)
Net income (loss)	(42,613)				(42,613)
Balances at Dec. 31, 2013	76,947	758	410,350		(334,161)
Balance, Shares at Dec. 31, 2013	75,803,020	75,803,020
Common stock issued under equity incentive and employee stock purchase plans, net of shares withheld for employee taxes, Amount	33,882	23	33,859
Common stock issued under equity incentive and employee stock purchase plans, net of shares withheld for employee taxes, Shares		2,314,207
Stock-based compensation expense	45,134		45,134
Excess tax benefits from stock-based compensation	16,965		16,965
Tax shortfalls from stock-based compensation	(77)		(77)
Repayment of Convertible Notes	(4)		(4)
Net income (loss)	276,452				276,452
Balances at Dec. 31, 2014	$ 449,299	$ 781	$ 506,227		$ (57,709)
Balance, Shares at Dec. 31, 2014	78,117,227	78,117,227