Loans (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Jan. 01, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Summary of classes of loans (abstract)
Loans and receivable	$ 2,653,861	$ 2,767,125			$ 2,710,144
Net unamortized fees and costs	927				938
Total	2,654,788				2,711,082
Less allowance for credit losses and loan losses	35,590	37,060	$ 35,940	$ 37,070	37,070	$ 37,620	$ 33,760
Loans and receivable, net	2,619,198				2,674,012
Loans and Leases Receivable, Allowance	35,590				37,070
financing receivable, allowance for credit loss, change due to economic factors	1,140
Financing Receivable, Allowance for Credit Losses, change due to loan volume	750
Financing Receivable, Allowance for Credit Losses, change in prepayment and curtailment rates	1,030
Financing Receivable, Allowance for Credit Losses, change due to historical loss rates	1,590
Impact of ASC 326 Adoption
Summary of classes of loans (abstract)
Less allowance for credit losses and loan losses				$ 2,746	2,746
Agricultural [Member]
Summary of classes of loans (abstract)
Loans and receivable	94,210	96,321			94,842
Total	94,210
Less allowance for credit losses and loan losses	2,118	2,595	2,055		2,508	2,547	2,400
Agricultural [Member] | Impact of ASC 326 Adoption
Summary of classes of loans (abstract)
Less allowance for credit losses and loan losses					(328)
Commercial and Financial [Member]
Summary of classes of loans (abstract)
Loans and receivable	228,181	335,463			286,242
Total	228,181
Less allowance for credit losses and loan losses	4,348	5,345	4,802		4,885	5,777	4,988
Commercial and Financial [Member] | Impact of ASC 326 Adoption
Summary of classes of loans (abstract)
Less allowance for credit losses and loan losses					298
Commercial and Financial [Member] | Small Business Administration SBA, CARES Act, Paycheck Protection Program
Summary of classes of loans (abstract)
Loans and Leases Receivable, Before Unamortized Fees and Costs	24,550				86,500
Loans and Leases Receivable, Deferred Loan Fees included with Loans	330				2,120
Interest and fee income, Loans and Leases, PPP Loan fees recognized in income	5,480	1,260
Payment for (Proceeds from) Loans and Leases, Payment of PPP loans forgiven	160,480	0
Real Estate Construction One to Four Family Residential [Member]
Summary of classes of loans (abstract)
Loans and receivable	73,167				71,117
Total	73,167
Real Estate: Construction, land development and commercial [Member]
Summary of classes of loans (abstract)
Loans and receivable	118,623				111,913
Total	118,623
Real Estate: Mortgage, farmland [Member]
Summary of classes of loans (abstract)
Loans and receivable	241,650	243,689			247,142
Total	241,650
Less allowance for credit losses and loan losses	4,663	$ 4,048	$ 4,904		4,173	$ 4,089	$ 3,950
Real Estate: Mortgage, farmland [Member] | Impact of ASC 326 Adoption
Summary of classes of loans (abstract)
Less allowance for credit losses and loan losses					763
Real Estate: Mortgage, 1 to 4 family first liens [Member]
Summary of classes of loans (abstract)
Loans and receivable	898,333				892,089
Total	898,333
Real Estate: Mortgage, 1 to 4 family junior liens [Member]
Summary of classes of loans (abstract)
Loans and receivable	115,308				127,833
Total	115,308
Real Estate: Mortgage, multi-family [Member]
Summary of classes of loans (abstract)
Loans and receivable	389,805				374,014
Total	389,805
Real Estate: Mortgage, commercial [Member]
Summary of classes of loans (abstract)
Loans and receivable	410,050				417,139
Total	410,050
Loans to individuals [Member]
Summary of classes of loans (abstract)
Loans and receivable	32,235				31,325
Total	32,235
Obligations of state and political subdivisions [Member]
Summary of classes of loans (abstract)
Loans and receivable	52,299				$ 56,488
Total	$ 52,299