Stockholders' Equity - Option and Restricted Stock Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Options Outstanding, Number of Shares
Shares and Units Available for Grant, Beginning balance	5,755
Additional shares reserved under the 2012 equity incentive plan	3,279
Shares and Units Available for Grant, Granted	(4,602)
Shares and Units Available for Grant, Options exercised/ Restricted stock released	0
Shares and Units Available for Grant, Canceled/Forfeited	3,739
Shares and Units Available for Grant, Ending balance	8,171
Employee Stock Option
Options Outstanding, Number of Shares
Options Outstanding, Number of Shares, Beginning Balance	8,908
Additional shares reserved under the 2012 equity incentive plan	0
Options Outstanding, Number of Shares, Granted	1,757
Options Outstanding, Number of Shares, Options exercised/ Restricted stock released	(514)
Options Outstanding, Number of Shares, Canceled /Forfeited	(1,842)
Options Outstanding, Number of Shares, Ending Balance	8,309
Options Outstanding, Options, Weighted Average Exercise Price
Options Outstanding, Weighted Average Exercise Price, Beginning Balance	$ 5.89
Options Outstanding, Weighted Average Exercise Price, Grants in Period	$ 5.13
Options Outstanding, Weighted Average Exercise Price, Options exercised/ Restricted stock released in Period	$ 5.17
Options Outstanding, Weighted Average Exercise Price, Forfeitures in Period	$ 6.46
Options Outstanding, Weighted Average Exercise Price, Ending Balance
Restricted Stock Outstanding
Options Outstanding, Number of Shares
Restricted Stock Outstanding Number of Share, Beginning balance	5,431
Additional shares reserved under the 2012 equity incentive plan	2,845
Restricted Stock Outstanding Number of Share, Granted	(927)
Restricted Stock Outstanding Number of Share, Options exercised/ Restricted stock released	0
Restricted Stock Outstanding Number of Share, Canceled /Forfeited	(1,892)
Restricted Stock Outstanding Number of Share, Ending balance	5,457