Equity Incentive Plan - Schedule of Stock Option Activity Under 2016 Plan (Detail) - 2016 Plan [Member] - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options outstanding, beginning balance	411,480	410,310
Options granted	67,050	84,270
Options forfeited	(32,860)	(74,255)
Options expired	(8,640)	(8,845)
Options outstanding, ending balance		411,480	410,310
Options cancelled	(437,030)
Weighted average exercise price, beginning balance	$ 100	$ 100
Weighted average exercise price, granted	90	100
Weighted average exercise price, forfeited	99	100
Weighted average exercise price, expired	99	100
Weighted average exercise price, ending balance		$ 100	$ 100
Weighted average exercise price, cancelled	$ 100
Weighted average remaining contractual term, balance		8 years 3 months 18 days	8 years 9 months 18 days