Net Income (Loss) per Share of Common Stock (Details) - 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
Numerator
Net income (loss) (in thousands)	$ 40,606	$ 2,147	$ 1,178	$ (2,129)	$ 1,317	$ 4,782	$ 2,769	$ (7,337)	$ 41,802	$ 1,531	$ (19,305)
Denominator
Weighted average shares of common stock outstanding used in computing net income (loss) per share, basic (shares)	39,093,825	38,881,183	38,649,873	38,383,022	37,958,395	37,630,222	37,440,537	37,215,697	38,754,643	37,563,590	36,209,051
Dilutive effect of incremental shares and share equivalents									2,041,003	3,433,382	0
Weighted average shares of common stock outstanding used in computing net income (loss) per share, diluted	40,966,744	40,860,593	41,641,660	38,383,022	41,434,178	40,926,034	40,597,275	37,215,697	40,795,646	40,996,972	36,209,051
Net income (loss) per share:
Net income (loss) per share, basic (dollars per share)	$ 1.04	$ 0.06	$ 0.03	$ (0.06)	$ 0.03	$ 0.13	$ 0.07	$ (0.20)	$ 1.08	$ 0.04	$ (0.53)
Net income (loss) per share, diluted (dollars per share)	$ 0.99	$ 0.05	$ 0.03	$ (0.06)	$ 0.03	$ 0.12	$ 0.07	$ (0.20)	$ 1.02	$ 0.04	$ (0.53)