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
	Mar. 31, 2024	Mar. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year gross charge-offs	$ 1
Fiscal year before current fiscal year gross charge-offs	1,269	$ 158
Two years before current fiscal year gross charge-offs	486	114
Three years before current fiscal year gross charge-offs	199	53
Four years before current fiscal year gross charge-offs	26	41
Prior gross charge-offs	164	64
Revolving Loans Amortized Cost Basis gross charge-offs	1,546	2
Total current-period gross charge-offs	3,691	432
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
Four years before current fiscal year gross charge-offs	1
Prior gross charge-offs		3
Total current-period gross charge-offs	13	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
Total current-period gross charge-offs		2
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	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	1
Three years before current fiscal year gross charge-offs	1
Prior gross charge-offs	21	2
Total current-period gross charge-offs	23	2
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
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	29	26
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	31
Three years before current fiscal year gross charge-offs		16
Four years before current fiscal year gross charge-offs		13
Prior gross charge-offs		2
Total current-period gross charge-offs	31	35
Commercial Non Real Estate Member
Financing Receivable, Credit Quality Indicator [Line Items]
Fiscal year before current fiscal year gross charge-offs	1,001	67
Two years before current fiscal year gross charge-offs	275	62
Three years before current fiscal year gross charge-offs	132
Four years before current fiscal year gross charge-offs	12
Prior gross charge-offs	126	47
Revolving Loans Amortized Cost Basis gross charge-offs	1,508
Total current-period gross charge-offs	3,054	176
Consumer Non Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Fiscal year before current fiscal year gross charge-offs	244	76
Two years before current fiscal year gross charge-offs	97	32
Three years before current fiscal year gross charge-offs	51	15
Four years before current fiscal year gross charge-offs	13	9
Prior gross charge-offs	15	6
Revolving Loans Amortized Cost Basis gross charge-offs	11	2
Total current-period gross charge-offs	431	$ 140
Oil and Gas [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Fiscal year before current fiscal year gross charge-offs	9
Two years before current fiscal year gross charge-offs	83
Total current-period gross charge-offs	$ 92