Net Income Per Share - Computation of Basic and Diluted Net Income (Loss) Per Share Attributable to Common Stockholders (Detail) - 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
Earnings Per Share [Abstract]
Net income (loss)	$ 22,780	$ (65,145)	$ 520	$ (9,158)	$ 2,838	$ 5,450	$ (1,498)	$ (4,295)	$ (51,003)	$ 2,495	$ 54,455
Denominator (basic):
Weighted average common shares outstanding									94,897,450	92,733,496	88,635,832
Denominator (diluted):
Weighted average common shares outstanding									94,897,450	92,733,496	88,635,832
Dilutive stock options outstanding									0	3,791,148	4,984,569
Dilutive restricted stock units and restricted stock awards									0	252,093	105,572
Dilutive shares purchased under ESPP									0	16,387	2,349
Weighted average common shares from warrants									0	2,308,808	2,318,422
Net weighted average common shares outstanding									94,897,450	99,101,932	96,046,744
Net income (loss) per share:
Basic (USD per share)	$ 0.24	$ (0.68)	$ 0.01	$ (0.10)	$ 0.03	$ 0.06	$ (0.02)	$ (0.05)	$ (0.54)	$ 0.03	$ 0.61
Diluted (USD per share)	$ 0.23	$ (0.68)	$ 0.01	$ (0.10)	$ 0.03	$ 0.06	$ (0.02)	$ (0.05)	$ (0.54)	$ 0.03	$ 0.57