Stock Compensation Plans - Summary of Stock Option Activity under the Company's Plan (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of options, Outstanding at beginning of year	5,191,666
Number of options, Granted	5,822,500	0
Number of options, Exercised or released	(186,665)
Number of options, Forfeited or cancelled	(270,001)
Number of options, Expired	(25,000)
Number of options, Outstanding at end of year	10,532,500	5,191,666
Number of options, Exercisable at end of year	4,349,996
Weighted average exercise price, Outstanding at beginning of year	$ 1.96
Weighted average exercise price, Granted	3.04
Weighted average exercise price, Exercised or released	1.59
Weighted average exercise price, Forfeited or cancelled	2.94
Weighted average exercise price, Expired	0.47
Weighted average exercise price, Outstanding at end of year	2.54	$ 1.96
Weighted average exercise price, Exercisable at end of year	$ 2.16
Weighted Average Remaining Contractual Term (Years), Outstanding at end of year	5 years 4 months 20 days
Weighted Average Remaining Contractual Term (Years), Exercisable at end of year	4 years
Aggregate Intrinsic value, Outstanding at end of year	$ 2,239,500
Aggregate Intrinsic value, Exercisable at end of year	$ 1,679,297