Computation of Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Computation of Net Income (Loss) per Share
Net income (loss) available to common stockholders	$ 6,101	$ (4,704)	$ 13,852	$ (11,430)
Weighted average common shares outstanding used in computing basic income (loss) per share	114,799	111,701	113,918	111,191
Incremental options and RSUs	7,063		6,702
Weighted average common shares outstanding used in computing diluted net income (loss) per share	121,862	111,701	120,620	111,191
Net income (loss) per share
Basic	$ 0.05	$ (0.04)	$ 0.12	$ (0.10)
Diluted	$ 0.05	$ (0.04)	$ 0.11	$ (0.10)
Incremental shares excluded from the calculation of net loss per share (in shares)		4,296		4,550