Stock Option Activity (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014
Number of Shares
Number of Shares, Outstanding at beginning of period	1,162,449
Number of Shares, Granted	1,340,690
Number of Shares, Exercised
Number of Shares, Forfeited and canceled	(45,511)
Number of Shares, Outstanding at end of period	2,457,628
Number of Shares, Exercisable at end of period	762,793
Weighted average exercise price
Weighted average exercise price, Outstanding at beginning of period	$ 4.30
Weighted average exercise price, Granted	$ 1.82
Weighted average exercise price, Exercised
Weighted average exercise price, Forfeited and canceled	$ 3.65
Weighted average exercise price, Outstanding at end of period	$ 2.96
Weighted average exercise price, Exercisable at end of period	$ 5.02
Weighted average remaining contract term
Weighted average remaining contract term, Outstanding at end of period	8 years 8 months 12 days
Weighted average remaining contract term, Exercisable at end of period	6 years 9 months 18 days
Intrinsic Value
Intrinsic Value, Outstanding at end of period	$ 153,522
Intrinsic Value, Exercisable at end of period	$ 68,356