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Medium- And Long-Term Debt (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Pledged to the FHLB as collateral for potential future borrowings - real estate related loans	$ 17,900
Pledged to the FHLB as collateral for potential future borrowings - investment securities	1,100
Short-term advances	500
Potential future borrowings	9,600
Fixed-to-floating rate subordinated note	500
Unamortized debt issuance cost	$ 9	$ 7
5.332% subordinated notes due 2033 | Subsidiaries
Debt Instrument [Line Items]
Maturity year	2033

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- Definition

Debt Instrument, Maturity Year

+ References

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- Definition

Fixed-to-floating rate subordinated notes

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- Definition

Pledged to the FHLB as collateral for potential future borrowings - investment securities

+ References

No definition available.

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- Definition

Pledged to the FHLB as collateral for potential future borrowings - real estate related loans

+ References

No definition available.

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- Definition

Short-term advances

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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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- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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