Amount, after recoveries, of loans and leases that have been written-off.

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Amount of expense (reversal of expense) for expected credit loss on investment in debt security measured at amortized cost (held-to-maturity).

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Amount, after allowance for credit loss, of accrued interest on financial asset measured at amortized cost.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Number of financing receivables that have been modified by troubled debt restructurings.

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Amount, after troubled debt restructuring, of modified financing receivable.

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Amount, before troubled debt restructuring, of financing receivable to be modified.

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Amount of financing receivable modified as troubled debt restructuring.

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Amount of financing receivable on nonaccrual status with no allowance for credit loss.

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Amount of allowance for credit losses related to recorded investment.

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Amount of expense related to estimated loss from loan and lease transactions.

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Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

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Financing Receivables, Modifications, Weighted Average Extension Term

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Financing Receivables, Modifications, Weighted Average Interest Only Term

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Loan Forgiveness

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Other Real Estate, Foreclosed Assets, and Repossessed Assets, In Process

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Weighted average decrease stated interest rate - basis points

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Allowance for Credit Losses (Narrative) (Details)	3 Months Ended		12 Months Ended
Allowance for Credit Losses (Narrative) (Details)	Mar. 31, 2022 USD ($) contract	Mar. 31, 2021 USD ($) contract	Mar. 31, 2022 USD ($) contract	Mar. 31, 2021 USD ($) contract	Dec. 31, 2021 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Accrued interest related to financial assets held at amortized cost	$ 124,400,000	$ 128,800,000	$ 124,400,000	$ 128,800,000	$ 117,400,000
Nonaccrual loans with no related allowance for credit losses	27,600,000		$ 27,600,000
Loans reasonably expected to be modified into TDRs	218,000
Provision for (reversal of) credit losses	4,025,000	$ (45,386,000)
Loan net charge-offs	2,500,000
Provision for credit losses	$ 159,000
TDRs, count \| contract	13	20	57	106
Foreclosed residential real estate properties	$ 1,100,000		$ 1,100,000
TDRs, balance	$ 3,097,000	$ 2,126,000	14,839,000	$ 24,201,000
Weighted average extension term	71 months	110 months
Weighted average decrease in stated interest rate	0.79%	1.27%
Interest-only payment terms	4 months	6 months
Loan forgiveness	$ 0	$ 0
Financing Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans modified in TDRs	$ 44,900,000		44,900,000
TDRs, count \| contract	227
Allowance for loan losses related to impaired loans	$ 2,600,000		2,600,000
Residential Real Estate \| Financing Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Recorded investment, foreclosure proceedings in process	$ 7,700,000	$ 13,800,000	$ 7,700,000	$ 13,800,000