Stock Based Awards - Stock Options Outstanding and Exercisable under Stock Option Plans (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number	2,723,366
Options Exercisable and Vested, Outstanding Number	648,058
$1.27 - $1.61 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Limit	$ 1.27
Range of Exercise Price, Upper Limit	$ 1.61
Options Outstanding, Number	769,755
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	7 years 6 months
Options Exercisable and Vested, Outstanding Number	471,420
$2.53 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Limit	$ 2.53
Range of Exercise Price, Upper Limit	$ 2.53
Options Outstanding, Number	570,927
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	9 years
Options Exercisable and Vested, Outstanding Number	146,484
Options Exercisable and Vested, Weighted Average Remaining Contractual Life (Years)	9 years
$3.34 - $18.66 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Limit	$ 3.34
Range of Exercise Price, Upper Limit	$ 18.66
Options Outstanding, Number	576,987
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	9 years 2 months 12 days
Options Exercisable and Vested, Outstanding Number	1,087
Options Exercisable and Vested, Weighted Average Remaining Contractual Life (Years)	9 years 2 months 12 days
$18.73 - $31.96 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Limit	$ 18.73
Range of Exercise Price, Upper Limit	$ 31.96
Options Outstanding, Number	795,697
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	9 years 7 months 6 days
Options Exercisable and Vested, Outstanding Number	29,067
Options Exercisable and Vested, Weighted Average Remaining Contractual Life (Years)	9 years 7 months 6 days
$34.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Limit	$ 34.00
Range of Exercise Price, Upper Limit	$ 34.00
Options Outstanding, Number	10,000
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	9 years 6 months
Options Exercisable and Vested, Weighted Average Remaining Contractual Life (Years)	9 years 6 months