Computation of Net Earnings (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Computation of Net Earnings (Loss) per Share
Net income (loss) available to common stockholders	$ 5,883	$ (6,900)	$ 7,751	$ (6,726)
Weighted average common shares outstanding used in computing basic earning (loss) per share	113,784	111,212	113,470	110,932
Incremental options and RSUs	6,828		6,430
Weighted average common shares outstanding used in computing diluted net earnings (loss) per share	120,612	111,212	119,900	110,932
Net earnings (loss) per share
Basic	$ 0.05	$ (0.06)	$ 0.07	$ (0.06)
Diluted	$ 0.05	$ (0.06)	$ 0.06	$ (0.06)
Incremental shares excluded from the calculation of net loss per share (in shares)		4,047		4,625