Equity Incentive Plans and Stock-Based Compensation (Details 2) (Employee Stock Option [Member], USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Employee Stock Option [Member]
Number of Shares
Outstanding, at the beginning of the period (in shares)			11,377,146
Options granted (in shares)	118,615	136,875	1,916,077	1,756,312
Options exercised (in shares)			(464,254)
Options forfeited (in shares)			(863,102)
Outstanding, at the end of the period (in shares)	11,965,867		11,965,867
Vested or expected to vest at the end of the period (in shares)	11,205,432		11,205,432
Options exercisable at the end of the period (in shares)	5,904,488		5,904,488
Weighted Average Exercise Price
Outstanding at the beginning of the year (in dollars per shares)			$ 11.32
Options granted (in dollars per share)			$ 8.96
Options exercised (in dollars per share)			$ 6.73
Options forfeited (in dollars per share)			$ 16.99
Outstanding at the end of the period (in dollars per shares)	$ 10.71		$ 10.71
Vested or expected to vest at the end of the period (in dollars per share)	$ 10.94		$ 10.94
Options exercisable at the end of the period (in dollars per share)	$ 14.41		$ 14.41
Weighted Average Remaining Contractual Term
Outstanding			6 years 2 months 8 days
Vested or expected to vest			6 years 7 days
Options exercisable			3 years 11 months 19 days
Aggregate Intrinsic Value
Outstanding	$ 65,861		$ 65,861
Vested or expected to vest	60,540		60,540
Options exercisable	$ 21,658		$ 21,658