Summary of Information Regarding Option Activity (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Options Outstanding
Options outstanding at January 1, 2014	1,610,988		2,231,590
Granted	181,431
Exercised	(114,942)
Forfeited/Cancelled	(2,400)
Options outstanding at March 31, 2014	1,675,077		2,231,590
Options exercisable at March 31, 2014	834,186
Vested and expected to vest at March 31, 2014	1,577,600	[1]
Weighted-Average Exercise Price Per Share
Options outstanding at January 1, 2014	$ 5.07		$ 4.40
Granted	$ 11.14
Exercised	$ 4.54
Forfeited/Cancelled	$ 5.12
Options outstanding at March 31, 2014	$ 5.78		$ 4.40
Options exercisable at March 31, 2014	$ 4.29
Vested and expected to vest at March 31, 2014	$ 5.67	[1]
Weighted-Average Remaining Contractual Term (in years)
Options outstanding at March 31, 2014	6 years 11 months 23 days
Options exercisable at March 31, 2014	5 years 1 month 17 days
Vested and expected to vest at March 31, 2014	6 years 10 months 17 days	[1]
Aggregate Intrinsic Value
Options outstanding at March 31, 2014	$ 12,256,703
Options exercisable at March 31, 2014	7,146,702
Vested and expected to vest at March 31, 2014	$ 11,700,596	[1]

[1] This represents the number of vested options as of March 31, 2014 plus the number of unvested options expected to vest as of March 31, 2014 based on the unvested outstanding options at March 31, 2014 adjusted for estimated forfeiture rates of 8% for awards granted to non-executive level employees and 3% for awards granted to executive level employees.