Summary of Stock Option Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock Option Shares
Outstanding Beginning of year	2,522,522	2,417,659	1,415,009
Granted	2,283,719	1,269,470	1,595,375
Exercised	(241,056)	(371,353)	(25,291)
Canceled or expired	(374,818)	(793,254)	(567,434)
Outstanding at end of year	4,190,367	2,522,522	2,417,659
Exercisable at year end	1,051,329	615,394	742,211
Vested and expected to vest	3,467,069
Weighted Average Exercise Price
Outstanding at Beginning of year	$ 11.76	$ 11.18	$ 12.84
Granted	$ 34.18	$ 12.92	$ 9.18
Exercised	$ 11.31	$ 10.18	$ 6.54
Canceled or expired	$ 16.83	$ 12.59	$ 9.90
Outstanding at end of year	$ 23.46	$ 11.76	$ 11.18
Exercisable at year end	$ 11.91	$ 12.71	$ 15.60
Vested and expected to vest	$ 21.50
Aggregate Intrinsic Value
Outstanding at end of year	$ 18,544,313
Exercisable at end of year	9,856,124
Vested and expected to vest	$ 18,069,138
Weighted Average Remaining Contractual Life (Years)
Outstanding at end of year	8 years 6 months 29 days
Exercisable at end of year	7 years 15 days
Vested and expected to vest	8 years 4 months 28 days