Shareholders' Equity - Summary of Activity Related to Common Shares Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Equity [Abstract]
Common stock shares outstanding, Beginning balance	18,611,289	18,271,249
Issuance of common stock on exercise of stock options	19,606	73,680
Restricted stock awards, net of cancellations	202,748	189,578
Director share awards	60,998	79,918
Equity awards under Short-Term Incentive Plan	189,121	0
Issuance of common stock from purchase of Employee Stock Purchase Plan shares	157,706	180,859
Cancellation of stock for withholding tax for vested shares	(148,499)	(183,995)
Common stock Repurchases	(663,619)	0
Common stock shares outstanding, End of Year	18,429,350	18,611,289