Stock-Based Compensation - Option Activity under the Company's Stock Option Plans (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Number of Shares
Outstanding beginning of period (in shares)	31,706
Expired (in shares)	(28,942)
Outstanding at end of period (in shares)	2,764	31,706
Options exercisable at year-end (in shares)	2,764
Weighted Average Exercise Price
Outstanding beginning of period (in usd per share)	$ 7.76
Exercised (in usd per share)	7.83
Outstanding end of period (in usd per share)	6.94	$ 7.76
Options exercisable at year-end (in usd per share)	$ 6.94
Weighted Average Remaining Contractual Term (in Years)
Weighted average remaining contractual term (in years)	1 year 25 days	6 months 29 days
Options exercisable at year-end	1 year 25 days
Aggregate Intrinsic Value
Aggregate intrinsic value	$ 15,934	$ 305,120
Options exercisable at year-end	$ 15,934