Loans and Allowance for Credit Losses - Additional Information (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2022 USD ($) alternative Loan_modified	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) Loan_modified	Dec. 31, 2020 USD ($)	Jan. 01, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest on loans	$ 15,200,000		$ 14,700,000
Minimum value of loans individually measured for impairment	$ 250,000
Number of alternatives for measuring impaired loans receivable | alternative	3
Allowance for credit losses	$ 58,474,000	$ 55,418,000	54,655,000	$ 41,910,000
Interest lost on nonaccrual loans	95,000	154,000
Troubled debt restructurings balance	5,450,000		5,792,000
Loans receivable, modifications, allowance	$ 581,000		$ 765,000,000,000
Troubled debt restructurings balance | Loan_modified	3		1
Real estate acquired through foreclosure	$ 4,794,000		$ 4,984,000
Mortgage loans secured by real estate In foreclosure	$ 410,000		411,000
Accounting Standards Update 2016-13 | Financial Asset Acquired with Credit Deterioration | Restatement Adjustment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses					$ 833,000
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortization period of loans	25 years
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	20 years
Commercial Real Estate | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum loan-to-value ratio (in hundredths)	80.00%
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	$ 208,800,000
Non-residential Buildings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	874,100,000
Residential Buildings and Dwellings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	537,700,000
Real Estate Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings balance	$ 4,704,000		4,953,000
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	$ 402,700,000		430,800,000
Increase (decrease) in accounts and notes receivable	$ (28,100,000)
Maximum loan-to-value ratio (in hundredths)	65.00%
Amortization period of loans	25 years
Loans receivable, time period	1 year
Agricultural | Corn and Other Grain Farming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 283,600,000		297,400,000
Increase (decrease) in accounts and notes receivable	(13,800,000)
Agricultural | Real Estate Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses	$ 1,971,000	1,628,000	1,257,000	1,084,000
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	7 years
Loans receivable, time period	1 year
Allowance for credit losses	$ 17,348,000	$ 18,954,000	19,241,000	$ 13,485,000
Troubled debt restructurings balance	$ 459,000		$ 479,000
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	25 years