Summary of Significant Accounting Policies (Details 2) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Numerator
Net loss	$ (17,169)	$ (19,177)	$ (27,461)	$ (38,161)
Denominator
Weighted average common shares outstanding	65,449	34,022	65,409	34,021
Weighted average shares subject to repurchase	0	(4)	0	(6)
Weighted average shares outstanding, basic and diluted	65,449	34,018	65,409	34,015
Basic and diluted net loss per share	$ (0.26)	$ (0.56)	$ (0.42)	$ (1.12)