Consolidated Statements Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2012		86,561,320
Beginning balance at Dec. 31, 2012	$ 219,966	$ 87	$ 439,883	$ 0	$ (220,004)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option and warrant exercises (in shares)		4,659,232
Stock option and warrant exercises	14,878	$ 5	14,873
Common shares surrendered on net settlement of option and warrant exercises (in shares)		(38,141)
Common shares surrendered on net settlement of option and warrant exercises	(204)	$ (1)	(203)
Shares purchased under ESPP (in shares)		107,074
Shares purchased under ESPP	819		819
Share-based compensation	11,111		11,111
Vesting of restricted stock units and awards (in shares)		136,886
Restricted stock units surrendered in lieu of withholding taxes (in shares)		(29,374)
Restricted stock units and awards surrendered in lieu of withholding taxes	(436)		(436)
Restricted stock issued (in shares)		(44,774)
Other comprehensive loss	(18)			(18)
Net income (loss)	54,455				54,455
Ending balance at Dec. 31, 2013	300,571	$ 91	466,047	(18)	(165,549)
Ending balance (in shares) at Dec. 31, 2013		91,441,771
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option and warrant exercises (in shares)		2,184,126
Stock option and warrant exercises	10,959	$ 2	10,957
Common shares surrendered on net settlement of option and warrant exercises (in shares)		(24,905)
Common shares surrendered on net settlement of option and warrant exercises	(112)		(112)
Shares purchased under ESPP (in shares)		180,572
Shares purchased under ESPP	1,981		1,981
Share-based compensation	18,147		18,147
Vesting of restricted stock units and awards (in shares)		235,354
Vesting of restricted stock units and awards		$ 1	(1)
Restricted stock units surrendered in lieu of withholding taxes (in shares)		(72,176)
Restricted stock units and awards surrendered in lieu of withholding taxes	(1,107)		(1,107)
Restricted stock issued (in shares)		(44,774)
Other comprehensive loss	(98)			(98)
Net income (loss)	2,495				2,495
Ending balance at Dec. 31, 2014	332,836	$ 94	495,912	(116)	(163,054)
Ending balance (in shares) at Dec. 31, 2014		93,899,968
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option and warrant exercises (in shares)		1,358,761
Stock option and warrant exercises	9,325	$ 1	9,324
Common shares surrendered on net settlement of option and warrant exercises (in shares)		(835)
Shares purchased under ESPP (in shares)		169,763
Shares purchased under ESPP	2,194		2,194
Share-based compensation	27,920		27,920
Vesting of restricted stock units and awards (in shares)		629,124
Vesting of restricted stock units and awards		$ 1	(1)
Restricted stock units surrendered in lieu of withholding taxes (in shares)		(224,543)
Restricted stock units and awards surrendered in lieu of withholding taxes	(2,961)		(2,961)
Other comprehensive loss	(245)			(245)
Net income (loss)	(51,003)
Ending balance at Dec. 31, 2015	$ 318,066	$ 96	$ 532,388	$ (361)	$ (214,057)
Ending balance (in shares) at Dec. 31, 2015		95,832,238