Calculation of Earnings Per Share - Calculation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations, Per Basic Share	$ 2.09	$ 1.97
Calculation of Basic Earnings Per Share:
Net Income	$ 36,933	$ 34,466
Weighted shares outstanding (shares)	17,678,060	17,485,866
Basic Earnings Per Share (in dollars per share)	$ 2.09	$ 1.97
Reconciliation of Numerator:
Net Income	$ 36,933	$ 34,466
Reconciliation of Denominator:
Weighted shares outstanding - Basic (shares)	17,678,060	17,485,866
Effect of dilutive securities:
Share-based compensation (shares)	83,059	67,301
Adjusted denominator-Diluted (shares)	17,761,119	17,553,167
Income (Loss) from Continuing Operations, Per Diluted Share	$ 2.08	$ 1.96
Diluted Earnings Per Share (in dollars per share)	$ 2.08	$ 1.96
Net Income	$ 36,933	$ 34,466
Basic (shares)	17,678,060	17,485,866
Income (Loss) from Continuing Operations, Per Basic Share	$ 2.09	$ 1.97
Basic (in dollars per share)	$ 2.09	$ 1.97
Share-based compensation (shares)	83,059	67,301
Diluted (shares)	17,761,119	17,553,167
Income (Loss) from Continuing Operations, Per Diluted Share	$ 2.08	$ 1.96
Diluted (in dollars per share)	$ 2.08	$ 1.96
Retained Earnings [Member]
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	$ 36,933	$ 34,466
Calculation of Basic Earnings Per Share:
Net Income	36,933	34,466
Reconciliation of Numerator:
Net Income	36,933	34,466
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	36,933	34,466
Net Income	$ 36,933	$ 34,466