Summary of Stock Options Activity (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013
Options
Options, Outstanding beginning balance	1,030,795
Options, Granted	1,010,326
Options, Exercised	(149,147)
Options, Forfeited	(51,475)
Options, Outstanding ending balance	1,840,499
Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding beginning balance	$ 2.68
Weighted Average Exercise Price, Granted	$ 5.91
Weighted Average Exercise Price, Exercised	$ 1.05
Weighted Average Exercise Price, Forfeited	$ 2.92
Weighted Average Exercise Price, Outstanding ending balance	$ 4.58
Weighted-average fair value of options granted during the period	$ 3.19