Earnings Per Share - Computation of Basic and Diluted Net Income per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net income available to common stockholders	$ 7,409	$ 18,346	$ 35,441	$ 28,228
Denominator:
Weighted average shares used to compute net income per share attributable to common stockholders, basic (in shares)	109,559	105,093	108,510	104,568
Weighted average effect of potentially dilutive shares to purchase common stock (in shares)	7,508	2,254	5,420	2,343
Weighted average shares used to compute net income per share attributable to common stockholders, diluted (in shares)	117,067	107,347	113,930	106,911
Net income per share available to common stockholders
Basic (in dollars per share)	$ 0.07	$ 0.17	$ 0.33	$ 0.27
Diluted (in dollars per share)	$ 0.06	$ 0.17	$ 0.31	$ 0.26