Summary of Stock Options Outstanding by Exercise Price Range (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number of Options	9,957,367
Options Outstanding, Weighted Average Exercise Price	$ 8.72
Options Outstanding, Weighted Average Remaining Contractual Term	7 years 8 months 12 days
Options Vested and Exercisable, Number of Options	5,639,981
Options Vested and Exercisable, Weighted Average Exercise Price	$ 7.95
Options Vested and Exercisable, Weighted Average Remaining Contractual Term	7 years 2 months 12 days
$0.001 to 1.01
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	$ 0.001
Range of Exercise Prices, upper limit	$ 1.01
Options Outstanding, Number of Options	763,155
Options Outstanding, Weighted Average Exercise Price	$ 0.65
Options Outstanding, Weighted Average Remaining Contractual Term	4 years 6 months
Options Vested and Exercisable, Number of Options	748,363
Options Vested and Exercisable, Weighted Average Exercise Price	$ 0.64
Options Vested and Exercisable, Weighted Average Remaining Contractual Term	4 years 6 months
$2.35
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices	$ 2.35
Options Outstanding, Number of Options	1,011,650
Options Outstanding, Weighted Average Exercise Price	$ 2.35
Options Outstanding, Weighted Average Remaining Contractual Term	6 years 7 months 6 days
Options Vested and Exercisable, Number of Options	888,997
Options Vested and Exercisable, Weighted Average Exercise Price	$ 2.35
Options Vested and Exercisable, Weighted Average Remaining Contractual Term	6 years 6 months
$6.79 to 8.92
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	$ 6.790
Range of Exercise Prices, upper limit	$ 8.92
Options Outstanding, Number of Options	3,669,357
Options Outstanding, Weighted Average Exercise Price	$ 7.95
Options Outstanding, Weighted Average Remaining Contractual Term	8 years
Options Vested and Exercisable, Number of Options	1,837,104
Options Vested and Exercisable, Weighted Average Exercise Price	$ 7.89
Options Vested and Exercisable, Weighted Average Remaining Contractual Term	7 years 6 months
$9.03 to 11.59
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	$ 9.030
Range of Exercise Prices, upper limit	$ 11.59
Options Outstanding, Number of Options	2,771,210
Options Outstanding, Weighted Average Exercise Price	$ 10.84
Options Outstanding, Weighted Average Remaining Contractual Term	8 years 2 months 12 days
Options Vested and Exercisable, Number of Options	1,190,164
Options Vested and Exercisable, Weighted Average Exercise Price	$ 10.97
Options Vested and Exercisable, Weighted Average Remaining Contractual Term	8 years 2 months 12 days
$11.61 to 27.03
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	$ 11.610
Range of Exercise Prices, upper limit	$ 27.03
Options Outstanding, Number of Options	1,741,995
Options Outstanding, Weighted Average Exercise Price	$ 14.20
Options Outstanding, Weighted Average Remaining Contractual Term	8 years 2 months 12 days
Options Vested and Exercisable, Number of Options	975,353
Options Vested and Exercisable, Weighted Average Exercise Price	$ 15.11
Options Vested and Exercisable, Weighted Average Remaining Contractual Term	7 years 10 months 24 days