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
Earnings Per Share, Basic and Diluted [Abstract]
Net loss	$ (8,990)	$ (5,857)	$ (12,655)	$ (29,256)
Shares used in computing basic and diluted net loss per share	62,730	61,327	62,407	59,224
Basic and diluted net loss per share (usd per share)	$ (0.14)	$ (0.10)	$ (0.20)	$ (0.49)
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	3,017	4,390	3,024	4,585
Common stock options
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,390	3,484	2,411	3,679
Restricted stock awards
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	398	487	394	487
Restricted stock units
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	229	419	219	419