Stock Based Compensation - Company's Options Outstanding (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 of Shares	3,294,822
Options Exercisable - Number of Shares	1,423,760
Exercise Price Range 0.32 - 1.92 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Minimum	$ 0.32
Exercise Price, Maximum	$ 1.92
Options Outstanding - Number of Shares	787,662
Options Outstanding -Weighted- Average Remaining Contractual Life in Years	7 years 1 month 2 days
Options Exercisable - Number of Shares	570,418
Options Exercisable - Weighted- Average Remaining Contractual Life in Years	7 years 15 days
Exercise Price Range 2.24 - 3.84 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Minimum	$ 2.24
Exercise Price, Maximum	$ 3.84
Options Outstanding - Number of Shares	359,622
Options Outstanding -Weighted- Average Remaining Contractual Life in Years	5 years 4 months 2 days
Options Exercisable - Number of Shares	358,138
Options Exercisable - Weighted- Average Remaining Contractual Life in Years	5 years 4 months 2 days
Exercise Price Range 5.12 - 6.72 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Minimum	$ 5.12
Exercise Price, Maximum	$ 6.72
Options Outstanding - Number of Shares	389,070
Options Outstanding -Weighted- Average Remaining Contractual Life in Years	7 years 10 months 6 days
Options Exercisable - Number of Shares	200,015
Options Exercisable - Weighted- Average Remaining Contractual Life in Years	7 years 9 months 22 days
Exercise Price Range 8.96 - 12.50 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Minimum	$ 8.96
Exercise Price, Maximum	$ 12.50
Options Outstanding - Number of Shares	493,918
Options Outstanding -Weighted- Average Remaining Contractual Life in Years	9 years 29 days
Options Exercisable - Number of Shares	120,841
Options Exercisable - Weighted- Average Remaining Contractual Life in Years	8 years 8 months 16 days
Exercise Price Range 13.93 - 20.65 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Minimum	$ 13.93
Exercise Price, Maximum	$ 20.65
Options Outstanding - Number of Shares	1,264,550
Options Outstanding -Weighted- Average Remaining Contractual Life in Years	9 years 1 month 28 days
Options Exercisable - Number of Shares	174,348
Options Exercisable - Weighted- Average Remaining Contractual Life in Years	9 years 29 days