Loans and Allowance for Credit Losses - Additional Information (Details)	3 Months Ended	6 Months Ended
	Mar. 31, 2022 USD ($)	Jun. 30, 2023 USD ($) Loan_modified Alternative	Dec. 31, 2022 USD ($)	Jun. 30, 2022 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest on loans		$ 23,800,000	$ 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	$ 94,000	$ 122,000
Modified loans balance			5,064,000	$ 0
Troubled debt restructurings balance | Loan_modified		0
Real estate acquired through foreclosure		$ 3,978,000	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		$ 215,200,000
Non-residential Buildings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans		991,100,000
Residential Buildings and Dwellings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans		$ 473,700,000
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		$ 540,500,000	577,200,000
Increase (decrease) in accounts and notes receivable		$ (36,600,000)
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		$ 417,600,000	$ 445,200,000
Increase (decrease) in accounts and notes receivable		$ (27,700,000)
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