Computation of Net Loss per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Computation of Net Loss per Share
Net loss attributable to common stockholders	$ (4,750)	$ (8,718)	$ (17,758)	$ (19,216)
Weighted average common shares outstanding used in computing basic and diluted net loss per share	109,074	107,855	108,573	107,521
Net loss per share
Basic and Diluted (in dollars per share)	$ (0.04)	$ (0.08)	$ (0.16)	$ (0.18)
Number of incremental shares excluded from the calculation of net loss per share
Incremental shares excluded from the calculation of net loss per share (in shares)	4,383	1,010	2,620	1,508