Options Activity Under Option Plan (Detail) (USD $)	6 Months Ended
	Jun. 30, 2013
Share Based Compensation Arrangements By Share Based Payment Award Options [Line Items]
Balances, at December 31, 2012, Stock Options Issued and Outstanding	10,255,222
Options Granted, Stock Options Issued and Outstanding	1,566,750
Options Exercised, Stock Options Issued and Outstanding	(1,323,933)
Options Forfeited/Expired, Stock Options Issued and Outstanding	(60,002)
Balance, June 30, 2013, Stock Options Issued and Outstanding	10,438,037
Balances, at December 31, 2012, Weighted Average Exercise Price	$ 1.19
Options Granted, Weighted Average Exercise Price	$ 5.81
Options Exercised, Weighted Average Exercise Price	$ 0.43
Options Forfeited/Expired, Weighted Average Exercise Price	$ 1.70
Balances, June 30, 2013, Weighted Average Exercise Price	$ 1.98