Stock-Based Compensation - Schedule of Stock Option Activity under Equity Incentive Plans (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at the beginning, Shares	3,375,473
Granted, Shares	852,405
Exercised, Shares
Cancelled, Shares	(372,625)
Outstanding at the ending, Shares	3,855,253
Exercisable, Shares	2,881,588
Outstanding at the beginning, Weighted Average Exercise Price	$ 4.17
Granted, Weighted Average Exercise Price	$ 1.58
Exercised, Weighted Average Exercise Price
Canceled, Weighted Average Exercise Price	$ 3.52
Outstanding at the ending, Weighted Average Exercise Price	$ 3.66
Exercisable, Weighted Average Exercise Price	$ 4.27
Outstanding at the ending, Aggregate Intrinsic Value	$ 356
Exercisable, Aggregate Intrinsic Value	$ 131