Income Taxes - Reconciliation between applicable income taxes and statutory federal tax rate (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Tax amount
Taxes at statutory federal income tax rate	$ 14,506	$ 12,289	$ 8,168
Tax exempt income	(556)	(527)	(442)
State income taxes, net of federal benefits	2,973	2,522	1,618
Nondeductible items and other	(527)	(441)	12
Applicable income taxes	$ 16,396	$ 13,843	$ 9,356
Percentage of pretax income
Taxes at statutory federal income tax rate (as percentage)	21.00%	21.00%	21.00%
Tax exempt income (as percentage)	(0.80%)	(0.90%)	(1.10%)
State income taxes, net of federal benefits (as percentage)	4.30%	4.30%	4.20%
Nondeductible items and other (as percentage)	(0.80%)	(0.80%)
Applicable income taxes (as percentage)	23.70%	23.60%	24.10%

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other nondeductible expenses.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other nondeductible expenses.

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