Calculation of Earnings Per Share - Calculation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.71	$ 0.56	$ 3.46	$ 2.97
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share	$ 0	$ 0	$ 0	$ 0.01
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	$ 12,484	$ 9,280	$ 60,771	$ 48,981
Calculation of Basic Earnings Per Share:
Net Income	$ 12,475	$ 9,261	$ 60,754	$ 49,146
Weighted shares outstanding (shares)	17,582,115	16,533,748	17,538,461	16,466,106
Basic Earnings Per Share (in dollars per share)	$ 0.71	$ 0.56	$ 3.46	$ 2.98
Reconciliation of Numerator:
Net Income	$ 12,475	$ 9,261	$ 60,754	$ 49,146
Reconciliation of Denominator:
Weighted shares outstanding - Basic (shares)	17,582,115	16,533,748	17,538,461	16,466,106
Effect of dilutive securities:
Share-based compensation (shares)	77,528	59,094	71,697	57,094
Adjusted denominator-Diluted (shares)	17,659,643	16,592,842	17,610,158	16,523,200
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.71	$ 0.56	$ 3.45	$ 2.96
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share	0	0	0	0.01
Diluted Earnings Per Share (in dollars per share)	$ 0.71	$ 0.56	$ 3.45	$ 2.97
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax	$ (9)	$ (19)	$ (17)	$ 165
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	12,484	9,280	60,771	48,981
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax	(9)	(19)	(17)	165
Net Income	$ 12,475	$ 9,261	$ 60,754	$ 49,146
Basic (shares)	17,582,115	16,533,748	17,538,461	16,466,106
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.71	$ 0.56	$ 3.46	$ 2.97
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share	0	0	0	0.01
Basic (in dollars per share)	$ 0.71	$ 0.56	$ 3.46	$ 2.98
Share-based compensation (shares)	77,528	59,094	71,697	57,094
Diluted (shares)	17,659,643	16,592,842	17,610,158	16,523,200
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.71	$ 0.56	$ 3.45	$ 2.96
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share	0	0	0	0.01
Diluted (in dollars per share)	$ 0.71	$ 0.56	$ 3.45	$ 2.97
Retained Earnings [Member]
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	$ 12,484	$ 9,280	$ 60,771	$ 48,981
Calculation of Basic Earnings Per Share:
Net Income	12,475	9,261	60,754	49,146
Reconciliation of Numerator:
Net Income	12,475	9,261	60,754	49,146
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	12,484	9,280	60,771	48,981
Net Income	$ 12,475	$ 9,261	$ 60,754	$ 49,146