Loans - Narrative (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2022 USD ($) loan	Mar. 31, 2021 USD ($) loan	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Paycheck Protection Program	$ 136,000,000		$ 276,200,000
Financing Receivable, Paycheck Protection Program, Net of Deferred Fees	134,100,000		272,000,000
Financing Receivable, Paycheck Protection Program, Unearned Fees	1,900,000		4,200,000
Financing Receivable, Purchased with Credit Deterioration, Discount (Premium)	11,500,000		11,900,000
Federal Home Loan Bank, Advances, General Debt Obligations, Maximum Amount Available	2,900,000,000		2,500,000,000
Allowance for credit loss adjustment	41,000,000
Nonperforming loan balances, excluding government guaranteed balances			6,500,000
Other Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable	29,600,000		30,600,000
Enterprise Value Lending Portfolio Niche Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit loss adjustment	7,000,000
Non-Covered Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, allowance for credit loss	139,212,000	$ 131,527,000	145,041,000	$ 136,671,000
Nonperforming loan balances, excluding government guaranteed balances	4,000,000
Interest income on nonaccrual loans	$ 0	$ 0
Number of loans restructured | loan	0	0
Non-Covered Loans | Enterprise Value Lending Portfolio Niche Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, allowance for credit loss	$ 19,100,000
Non-Covered Loans | Agriculture Portfolio Niche Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, allowance for credit loss			$ 18,200,000
Cumulative Effect, Period Of Adoption, Adjustment | Non-Covered Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, allowance for credit loss	$ 14,700,000