Loans and Allowance for Credit Losses - Additional Information (Details)	9 Months Ended
	Sep. 30, 2023 USD ($) Loan_modified Alternative	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest on loans	$ 29,700,000		$ 23,000,000
Minimum value of loans individually measured for impairment	$ 250,000,000
Number of alternatives for measuring impaired loans receivable | Alternative	3
Interest lost on nonaccrual loans	$ 173,000	$ 168,000
Modified loans balance		$ 0	5,064,000
Troubled debt restructurings balance | Loan_modified	0
Real estate acquired through foreclosure	$ 2,296,000		4,261,000
Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Debt coverage ratio	1.20x
Commercial Real Estate | Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum loan-to-value ratio (in hundredths)	65.00%
Amortization period of loans	twenty
Commercial Real Estate | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum loan-to-value ratio (in hundredths)	80.00%
Amortization period of loans	twenty five years
1-4 Family Residential Properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period when loans charged-down	180 days
Motels and Hotels Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 227,200,000
Non-residential Buildings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	1,077,500,000
Residential Buildings and Dwellings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 532,800,000
Unsecured Open-end Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period when loans charged-down	180 days
Other Secured Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period when loans charged-down	120 days
Agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 580,500,000		577,200,000
Increase (decrease) in accounts and notes receivable	$ 3,300,000
Maximum loan-to-value ratio (in hundredths)	65.00%
Amortization period of loans	twenty-five years
Loans receivable, time period	1 year
Agricultural | Corn and Other Grain Farming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 452,900,000		$ 445,200,000
Increase (decrease) in accounts and notes receivable	$ 7,600,000
Commercial and Industrial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum loan-to-value ratio (in hundredths)	80.00%
Amortization period of loans	seven years
Loans receivable, time period	1 year
Residential Properties | Real Estate Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum loan-to-value ratio (in hundredths)	80.00%
Amortization period of loans	twenty-five years