Preferred Stock, Common Stock and Stockholders' Equity - Summary of Stock Option Activity (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Outstanding beginning balance	3,017,624
Options, Outstanding ending balance	3,114,371	3,017,624
2007 Plan and 2013 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Outstanding beginning balance	3,017,624
Options, Granted/Exchanged	2,672,246
Options, Expired/Forfeited/Exchanged	(2,575,499)
Options, Outstanding ending balance	3,114,371	3,017,624
Options, Vested and expected to vest at December 31, 2019	3,114,371
Options, Exercisable at December 31, 2019	1,230,605
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Outstanding beginning balance	$ 3.11
Weighted Average Exercise Price, Granted/Exchanged	1.20
Weighted Average Exercise Price, Expired/Forfeited/Exchanged	2.82
Weighted Average Exercise Price, Outstanding ending balance	1.71	$ 3.11
Weighted Average Exercise Price, Vested and expected to vest at December 31, 2019	1.71
Weighted Average Exercise Price, Exercisable at December 31, 2019	$ 3.17
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 3 months 26 days	7 years 8 months 5 days
Weighted Average Remaining Contractual Term (Years), Granted/Exchanged	9 years 4 months 9 days
Weighted Average Remaining Contractual Term (Years), Expired/Forfeited/Exchanged	7 years 5 months 23 days
Weighted Average Remaining Contractual Term (Years), Vested and expected to vest at December 31, 2019	8 years 3 months 26 days
Weighted Average Remaining Contractual Term (Years), Exercisable at December 31, 2019	6 years 8 months 12 days
Share Based Compensation Arrangement by Share Based Payment Award Options Outstanding, Aggregate Intrinsic Value [Abstract]
Aggregate Intrinsic Value, Outstanding beginning balance	$ 382,160
Aggregate Intrinsic Value, Outstanding ending balance	2,143,756	$ 382,160
Aggregate Intrinsic Value, Vested and expected to vest at December 31, 2019	2,143,756
Aggregate Intrinsic Value, Exercisable at December 31, 2019	$ 392,604