Investments (Securities Gains and Losses Recognized in Income) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Investments [Abstract]
Available-for-sale, gross gains	$ 0	$ 1
Available-for-sale, gross losses	0	1
Trading, gross gains	10	3
Trading, gross losses	9	3
Other noninterest-bearing investments, Nonmarketable equity securities, Gross gains	6	4
Other noninterest-bearing investments, Nonmarketable equity securities, Gross losses	9	3
Gross gains	16	8
Gross losses	18	7
Securities gains (losses), net	$ (2)	$ 1

Amount of unrealized and realized gain (loss) on investment in debt and equity securities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(7)(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(9)(a))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

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- Definition

Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-9

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Amount of realized loss on 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 realized gain on investment in debt security measured at fair value with change in fair value recognized in net income (trading).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-14

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Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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Debt and Equity Securities, Realized Gross Gain

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Debt and Equity Securities, Realized Gross Loss

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Other noninterest-bearing investments nonmarketable equity securities, gross gains.

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Other noninterest-bearing investments nonmarketable equity securities, gross losses.

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