Loans Held for investment and Allowance for Credit Losses on Loans - Gross charge-offs by year of origination (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year gross charge-offs	$ 29	$ 71	$ 30	$ 71
Fiscal year before current fiscal year gross charge-offs	434	224	1,703	382
Two years before current fiscal year gross charge-offs	199	135	685	249
Three years before current fiscal year gross charge-offs	52	358	251	411
Four years before current fiscal year gross charge-offs	25	29	51	70
Prior gross charge-offs	256	18	420	82
Revolving Loans Amortized Cost Basis gross charge-offs	382	15	1,928	17
Total current-period gross charge-offs	1,377	850	5,068	1,282
Real Estate Portfolio Segment [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Fiscal year before current fiscal year gross charge-offs				7
Two years before current fiscal year gross charge-offs				1
Three years before current fiscal year gross charge-offs			15	22
Four years before current fiscal year gross charge-offs				18
Total current-period gross charge-offs			15	48
Real Estate Portfolio Segment [Member] | Commercial Real Estate Non Owner Occupied [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Fiscal year before current fiscal year gross charge-offs			12
Three years before current fiscal year gross charge-offs	1		1
Four years before current fiscal year gross charge-offs			1
Prior gross charge-offs				3
Total current-period gross charge-offs	1		14	3
Real Estate Portfolio Segment [Member] | Construction And Development Less Than Sixty Months [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Fiscal year before current fiscal year gross charge-offs				2
Three years before current fiscal year gross charge-offs		2		2
Total current-period gross charge-offs		2		4
Real Estate Portfolio Segment [Member] | Construction Residential Real Estate Less Than Sixty Months [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Fiscal year before current fiscal year gross charge-offs			3
Total current-period gross charge-offs	0		3
Real Estate Portfolio Segment [Member] | Residential Real Estate First Lien [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year gross charge-offs	2		3
Fiscal year before current fiscal year gross charge-offs	23		23
Two years before current fiscal year gross charge-offs		19		19
Three years before current fiscal year gross charge-offs	2	21	3	21
Four years before current fiscal year gross charge-offs	4		4
Prior gross charge-offs	36	2	57	4
Total current-period gross charge-offs	67	42	90	44
Real Estate Portfolio Segment [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Fiscal year before current fiscal year gross charge-offs		2		4
Two years before current fiscal year gross charge-offs				19
Four years before current fiscal year gross charge-offs				1
Prior gross charge-offs			2	4
Revolving Loans Amortized Cost Basis gross charge-offs			27
Total current-period gross charge-offs		2	29	28
Real Estate Portfolio Segment [Member] | Agriculture Member
Financing Receivable, Credit Quality Indicator [Line Items]
Fiscal year before current fiscal year gross charge-offs				4
Two years before current fiscal year gross charge-offs	6		37
Three years before current fiscal year gross charge-offs	13	301	13	317
Four years before current fiscal year gross charge-offs		1		14
Prior gross charge-offs				2
Total current-period gross charge-offs	19	302	50	337
Commercial Non Real Estate Member
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year gross charge-offs	6	42	6	42
Fiscal year before current fiscal year gross charge-offs	155	34	1,156	101
Two years before current fiscal year gross charge-offs	43	1	318	63
Three years before current fiscal year gross charge-offs	8	20	140	20
Four years before current fiscal year gross charge-offs			12
Prior gross charge-offs	190	5	316	52
Revolving Loans Amortized Cost Basis gross charge-offs	378		1,886
Total current-period gross charge-offs	780	102	3,834	278
Consumer Non Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year gross charge-offs	21	29	21	29
Fiscal year before current fiscal year gross charge-offs	256	186	500	262
Two years before current fiscal year gross charge-offs	150	115	247	147
Three years before current fiscal year gross charge-offs	28	14	79	29
Four years before current fiscal year gross charge-offs	21	28	34	37
Prior gross charge-offs	30	11	45	17
Revolving Loans Amortized Cost Basis gross charge-offs	4	15	15	17
Total current-period gross charge-offs	$ 510	398	941	538
Oil and Gas [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Fiscal year before current fiscal year gross charge-offs		2	9	2
Two years before current fiscal year gross charge-offs			83
Total current-period gross charge-offs		$ 2	$ 92	$ 2