Stock-Based Compensation - SAR Activity (Detail) - Stock Appreciation Rights [Member] - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Stock Appreciation Rights Activity [Line Items]
SARs Outstanding, Beginning Balance	238,476	278,116	275,450
Granted, SARs	24,536	21,260	37,478
Exercised, SARs	(108,764)	(60,900)	(34,812)
Canceled, SARs	(2,229)	0	0
Shares Outstanding, SARs, Ending Balance	152,019	238,476	278,116
Outstanding, Weighted Average Grant Price Per Share, Beginning Balance	$ 19.26	$ 13.45	$ 9.79
Vested, SARs	103,094
Granted, Weighted Average Grant Price Per Share	$ 77.70	56.59	35.38
Exercisable, SARs	103,094
Exercised, Weighted Average Grant Price Per Share	$ 13.89	5.27	8.07
Canceled, Weighted Average Grant Price Per Share	77.70	0	0
Outstanding, Weighted Average Grant Price Per Share, Ending Balance	31.58	$ 19.26	$ 13.45
Vested, Weighted Average Grant Price Per Share	18.14
Exercisable, Weighted Average Grant Price Per Share	$ 18.14
Weighted Average Remaining Contractual Life, Outstanding	5 years 6 months
Weighted Average Remaining Contractual Life, Vested	4 years 1 month 6 days
Weighted Average Remaining Contractual Life, Exercisable	4 years 1 month 6 days
Aggregate Intrinsic Value, Outstanding	$ 8,862,501
Aggregate Intrinsic Value, Vested	7,396,470
Aggregate Intrinsic Value, Exercisable	$ 7,396,470