Off-Balance Sheet Credit Risk (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2022	Dec. 31, 2021
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
General settlement period of securities transactions	2 days
Fair value of securities accepted as collateral permitted to sell or repledge	$ 2,200.0	$ 2,300.0
Fair value of collateral securities sold or repledged	257.8	385.5
Outstanding commitments to originate loans	362.1	545.5
Letters of credit outstanding	30.6	22.9
Unfunded Commitment [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Expected credit losses for unfunded credit loss	37.0
Unused Lines Of Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Unused lines of credit to commercial and consumer borrowers	$ 5,900.0	$ 3,100.0
Standby Letters of Credit [Member] \| Maximum [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Letters of credit, expiration period	1 year

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Outstanding commitments to originate loans.

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Unused lines of credit to commercial and consumer borrowers.

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Fair value as of the balance sheet date of customer securities accepted as collateral by the entity that it is permitted by contract or custom to sell or re-pledge to counterparties as collateral.

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Fair value as of the balance sheet date of customer securities accepted as collateral by the entity that it has sold or re-pledged to counterparties as collateral.

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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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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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Period remaining on line of credit facility before it terminates, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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