Preferred Stock, Common Stock and Stockholders' Equity - Summary of Stock Option Activity (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Outstanding beginning balance	1,275,624
Options, Outstanding ending balance	2,131,624	1,275,624
2007 Plan and 2013 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Outstanding beginning balance	1,275,624
Options, Granted	856,000
Options, Outstanding ending balance	2,131,624	1,275,624
Options, Vested and expected to vest at December 31, 2017	2,131,624
Options, Exercisable at December 31, 2017	1,111,270
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Outstanding beginning balance	$ 4.04
Weighted Average Exercise Price, Granted	2.45
Weighted Average Exercise Price, Outstanding ending balance	3.40	$ 4.04
Weighted Average Exercise Price, Vested and expected to vest at December 31, 2017	3.40
Weighted Average Exercise Price, Exercisable at December 31, 2017	$ 4.08
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 21 days	8 years 4 months 2 days
Weighted Average Remaining Contractual Term (Years), Granted	9 years 1 month 17 days
Weighted Average Remaining Contractual Term (Years), Vested and expected to vest at December 31, 2017	8 years 21 days
Weighted Average Remaining Contractual Term (Years), Exercisable at December 31, 2017	7 years 4 months 17 days
Share Based Compensation Arrangement by Share Based Payment Award Options Outstanding, Aggregate Intrinsic Value [Abstract]
Aggregate Intrinsic Value, Outstanding beginning balance	$ 191,160
Aggregate Intrinsic Value, Outstanding ending balance	219,480	$ 191,160
Aggregate Intrinsic Value, Vested and expected to vest at December 31, 2017	219,480
Aggregate Intrinsic Value, Exercisable at December 31, 2017	$ 219,480