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	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]
Net income	$ 21,866	$ 11,856	$ 55,813	$ 28,718
Less: undistributed earnings allocated to participating securities	(681)	(6,018)	(15,257)	(14,844)
Net income attributable to common stockholders, basic	21,185	5,838	40,556	13,874
Add: undistributed earnings allocated to participating securities	70	290	1,353	586
Net income attributable to common stockholders, diluted	$ 21,255	$ 6,128	$ 41,909	$ 14,460
Weighted-average shares used in computing net income per share available to common stockholders, basic (in shares)	62,402	27,557	43,453	26,927
Add weighted-average effect of dilutive securities:
Stock options and RSAs (in shares)	7,161	2,848	5,795	2,308
Incremental Common Shares Attributable to Dilutive Effect of Employee Stock Purchase Plan	174	0	75	0
Stock purchase rights (in shares)	0	7	0	6
Weighted-average shares used in computing net income per share available to common stockholders, diluted (in shares)	69,737	30,412	49,323	29,241
Net income per share attributable to common stockholders:
Basic (usd per share)	$ 0.34	$ 0.21	$ 0.93	$ 0.52
Diluted (usd per share)	$ 0.30	$ 0.20	$ 0.85	$ 0.49