Loans and Allowance for Credit Losses - Troubled debt restructurings (TDRs) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts	64
Financing Receivable, Troubled Debt Restructuring	$ 3,851	$ 3,321
Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts	1
Financing Receivable, Troubled Debt Restructuring	$ 15	20
One- to four-family residential construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts	22
Financing Receivable, Troubled Debt Restructuring	$ 1,638	1,899
Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts	2
Financing Receivable, Troubled Debt Restructuring	$ 1,811	646
Commercial business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring		127
Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts	39
Financing Receivable, Troubled Debt Restructuring	$ 387	629
Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts	38
Financing Receivable, Troubled Debt Restructuring	$ 1,002
Financing Receivable, Troubled Debt Restructuring, Accruing Interest		2,350
Accruing | Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts	1
Financing Receivable, Troubled Debt Restructuring	$ 15
Financing Receivable, Troubled Debt Restructuring, Accruing Interest		20
Accruing | One- to four-family residential construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts	10
Financing Receivable, Troubled Debt Restructuring	$ 579
Financing Receivable, Troubled Debt Restructuring, Accruing Interest		1,121
Accruing | Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts	1
Financing Receivable, Troubled Debt Restructuring	$ 85
Financing Receivable, Troubled Debt Restructuring, Accruing Interest		646
Accruing | Commercial business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Accruing Interest		52
Accruing | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts	26
Financing Receivable, Troubled Debt Restructuring	$ 323
Financing Receivable, Troubled Debt Restructuring, Accruing Interest		511
Non-accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts	26
Financing Receivable, Troubled Debt Restructuring	$ 2,849	971
Non-accruing | One- to four-family residential construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts	12
Financing Receivable, Troubled Debt Restructuring	$ 1,059	778
Non-accruing | Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts	1
Financing Receivable, Troubled Debt Restructuring	$ 1,726
Non-accruing | Commercial business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring		75
Non-accruing | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts	13
Financing Receivable, Troubled Debt Restructuring	$ 64	$ 118