Income Tax Expense - Schedule of Components of Effective Income Tax Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020
Amount
Income before income tax expense									$ 40,060	$ 34,468
U.S. federal income tax expense									8,413	7,238
Nontaxable income									(1,347)	(1,045)
Nondeductible expenses									38	45
Other									4	85
Income tax expense	$ 1,771	$ 1,780	$ 1,869	$ 1,688	$ 1,582	$ 1,589	$ 1,531	$ 1,621	$ 7,108	$ 6,323
Percent
Income before income tax expense (as a percent)									100.00%	100.00%
U.S. federal income tax expense (as a percent)									21.00%	21.00%
Nontaxable income (as a percent)									(3.40%)	(3.00%)
Nondeductible expenses (as a percent)									0.10%	0.10%
Other (as a percent)									0.00%	0.20%
Income tax expense (as a percent)									17.70%	18.30%