Options Activity Under Option Plan (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [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	(2,100,402)
Options Forfeited/Expired, Stock Options Issued and Outstanding	(232,689)
Balance, September 30, 2013, Stock Options Issued and Outstanding	9,488,881
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	$ 0.73
Options Forfeited/Expired, Weighted Average Exercise Price	$ 2.03
Balances, September 30, 2013, Weighted Average Exercise Price	$ 2.03