Income Taxes - Summary of Reconciliation of Statutory Federal Tax and Effective Income Tax Rates (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Income Taxes Summary Of Reconciliation Of Statutory Federal Tax And Effective Income Tax Rates [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%		35.00%
Reconciliation of Effective Income Tax Rates Continuing Operations
Federal income tax expense (1)	[1]	$ 19,778	$ 17,264	$ 16,400
State income taxes, net of federal benefit		5,051	5,093	4,071
ESOP dividend deduction		(218)	(173)	(158)
Other		768	(1,070)	810
Income Tax Expense from Continuing Operations		$ 23,538	$ 21,114	$ 21,123
Effective Income Tax Rate for Continuing Operations		24.99%	25.65%	27.13%

[1] Federal income taxes were calculated at 21 percent for 2020, 2019, and 2018.