Stockholders' Equity - Common and Preferred Shares - Summary of the Company's Stock Option Activity under its 2005 Plan (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Options outstanding, Beginning Balance	192
Shares, Granted	438
Shares, Forfeited and expired	(15)
Shares, Options outstanding, Ending Balance	615
Shares, Options exercisable, Ending Balance	207
Shares, Options vested or expected to vest, Ending Balance	513
Weighted Average Exercise Price, Options outstanding, Beginning Balance	$ 12.54
Weighted Average Exercise Price, Granted	$ 2.77
Weighted Average Exercise Price, Forfeited and expired	$ 4.45
Weighted Average Exercise Price, Options outstanding, Ending Balance	$ 5.79
Weighted Average Exercise Price, Options exercisable, Ending Balance	$ 10.51
Weighted Average Exercise Price, Options vested or expected to vest, Ending Balance	$ 6.26
Weighted Average Remaining Contractual Life, Options Outstanding, Beginning Balance	7 years 7 months 10 days
Weighted Average Remaining Contractual Life, Options Outstanding, Ending Balance	8 years 6 months 29 days
Weighted Average Remaining Contractual Life, Options exercisable, Ending Balance	6 years 5 months 27 days
Weighted Average Remaining Contractual Life, Options vested or expected to vest, Ending Balance	8 years 4 months 13 days
Aggregate Intrinsic Value, Options outstanding, Ending Balance
Aggregate Intrinsic Value, Options exercisable outstanding, Ending Balance
Aggregate Intrinsic Value, Options vested or expected to vest, Ending Balance