Net Income Per Share Available to Common Stock - Basic and Diluted Net Income Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Net income	$ 86,850	$ 42,460	$ 21,349
Less: undistributed earnings allocated to participating securities	(17,961)	(21,683)	(11,727)
Net income attributable to common stockholders, basic	68,889	20,777	9,622
Add: undistributed earnings allocated to participating securities	1,635	1,003	40
Net income attributable to common stockholders, diluted	$ 70,524	$ 21,780	$ 9,662
Weighted-average shares used in computing net income per share available to common stockholders, basic (in shares)	48,427	27,320	24,711
Add weighted-average effect of dilutive securities:
Stock options and RSAs (in shares)	6,059	2,726	187
Employee stock purchase plan (in shares)	104	0	0
Stock purchase rights (in shares)	0	5	3
Weighted-average shares used in computing net income per share available to common stockholders, diluted (in shares)	54,590	30,051	24,901
Net income per share attributable to common stockholders:
Basic (in dollars per share)	$ 1.42	$ 0.76	$ 0.39
Diluted (in dollars per share)	$ 1.29	$ 0.72	$ 0.39