Equity Incentive Plans - Summary of Stock Option Activity (Detail) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share Based Compensation Arrangement By Share Based Payment Award Options Activity [Abstract]
Number of Shares Outstanding, Beginning Balance	8,207	7,205	7,856
Number of Shares Granted, Shares	2,815	2,592	260
Number of Shares Exercised, Shares	(1,683)	(50)	(25)
Number of Shares Forfeited or cancelled, Shares	(1,622)	(1,540)	(886)
Number of Shares Outstanding, Ending Balance	7,717	8,207	7,205
Weighted-Average Exercise Price, Beginning Balance	$ 4.55	$ 6.68	$ 7.12
Number of Share Exercisable	3,611
Weighted-Average Exercise Price, Granted	$ 2.18	$ 1.64	$ 2.03
Number of Shares Expected to vest	4,106
Weighted-Average Exercise Price, Exercised	$ 1.67	$ 0.46	$ 1.73
Weighted-Average Exercise Price, Forfeited or cancelled	$ 5.70	$ 9.72	$ 9.39
Weighted-Average Exercise Price, Ending Balance	$ 4.05	$ 4.55	$ 6.68
Weighted-Average Exercise Price Exercisable	$ 6.38
Weighted-Average Exercise Price Expected to Vest	$ 2.01
Weighted-Average Remaining Contractual Life (Years)	6 years 29 days
Weighted-Average Remaining Contractual Life (Years), Exercisable	2 years 11 months 16 days
Weighted-Average Remaining Contractual Life (Years), Expected to Vest	8 years 10 months 10 days
Aggregate Intrinsic Value, Exercised	$ 4,965	$ 45	$ 14
Aggregate Intrinsic Value	22,023
Aggregate Intrinsic Value, Exercisable	5,346
Aggregate Intrinsic Value Expected to Vest	$ 16,744