Preferred Stock, Common Stock and Stockholders' Equity - Summary of Stock Option Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares, Outstanding beginning balance	624,750
Shares, Granted	64,000
Shares, Exercised	(5,250)
Shares, Outstanding ending balance	683,500	624,750
Shares, Vested and expected to vest at December 31, 2014	683,500
Shares, Exercisable at December 31, 2014	259,081
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Outstanding beginning balance	$ 7.61
Weighted Average Exercise Price, Granted	$ 7.65
Weighted Average Exercise Price, Exercised	$ 0.29
Weighted Average Exercise Price, Outstanding ending balance	$ 7.67	$ 7.61
Weighted Average Exercise Price, Vested and expected to vest at December 31, 2014	$ 7.67
Weighted Average Exercise Price, Exercisable at December 31, 2014	$ 5.47
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding, Weighted Average Remaining Contractual Term [Abstract]
Weighted Average Remaining Contractual Term (Years), Outstanding	8 years 5 months 12 days	8 years 4 months 28 days
Weighted Average Remaining Contractual Term (Years), Granted	9 years 4 months 6 days
Weighted Average Remaining Contractual Term (Years), Exercised	2 years 8 months 12 days
Weighted Average Remaining Contractual Term (Years), Vested and expected to vest at December 31, 2014	8 years 5 months 12 days
Weighted Average Remaining Contractual Term (Years), Exercisable at December 31, 2014	7 years 7 months 24 days
Share Based Compensation Arrangement by Share Based Payment Award Options Outstanding, Aggregate Intrinsic Value [Abstract]
Aggregate Intrinsic Value, Outstanding beginning balance	$ 869,490
Aggregate Intrinsic Value, Exercised	33,810
Aggregate Intrinsic Value, Outstanding ending balance	649,000	869,490
Aggregate Intrinsic Value, Vested and expected to vest at December 31, 2014	649,000
Aggregate Intrinsic Value, Exercisable at December 31, 2014	$ 631,231