Investment Securities - Schedule of Investment Income (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Taxable interest	$ 244	$ 229	$ 489	$ 446
Taxable dividends	6	4	10	7
Interest and dividends exempt from U.S. federal income tax	5	5	11	11
Interest and dividends on investment securities	$ 255	$ 238	$ 510	$ 464

Amount of operating dividend income on securities subject to state, federal and other income tax.

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-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(2))
-Publisher FASB
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Amount of operating dividend and interest income, including amortization and accretion of premiums and discounts, on securities.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(1))
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-Subparagraph (SX 210.12-14(Column E)(Footnote 4))
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Interest income, including any amortization and accretion (as applicable) of discounts and premiums, derived from debt securities issued by municipal governments, local taxing districts and US state government agencies.

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Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities subject to state, federal and other income tax.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1402
-Paragraph a
-Publisher SEC

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-Subparagraph (SX 210.9-04(2))
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-Name Regulation S-K (SK)
-Number 229
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