Securities (Narrative) (Details)	Mar. 31, 2023 USD ($) Security	Dec. 31, 2022 USD ($) Security	Mar. 31, 2022 USD ($)
Debt and Equity Securities, FV-NI [Line Items]
Securities with an aggregate fair value	$ 5,415,262,000	$ 5,483,762,000
Securities available for sale, amortized cost	6,238,835,000	6,310,214,000
Securities classified as trading	0	$ 0
Allowance for credit loss	$ 0
Securities that met the criteria of a credit loss event \| Security	0
Number of securities with market values below their cost basis \| Security	709	757
Asset Pledged as Collateral without Right [Member]
Debt and Equity Securities, FV-NI [Line Items]
Securities pledged as collateral	$ 6,100,000,000	$ 4,900,000,000
Available for Sale and Held to Maturity [Member]
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost of securities excluding accrued interest		$ 29,100,000	$ 28,300,000

Available for sale securities amortized cost excluding accrued interest.

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Number of securities met criteria of credit loss event.

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Number of securities with market values below cost basis.

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Amount of allowance for credit loss of accounts and financing receivables. Includes, but is not limited to, notes and loan receivable.

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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