Derivative Financial Instruments - Impact on Derivatives and Hedged Items on Consolidated Statement of Income (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	$ (17)	$ 38	$ (484)
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	17	(38)	484
Net unrealized losses on AFS investment securities designated in fair value hedges recognized in OCI	93	122
Total available-for-sale investment securities \| Net interest income \| Interest rate contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	(55)	(164)	676
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	55	164	(676)
Long-term debt \| Net interest income \| Interest rate contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	17	202	(1,160)
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	(17)	(202)	1,160
Available-for-sale securities \| Other fee revenue \| Interest rate contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	21	0	0
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	$ (21)	$ 0	$ 0

Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 815
-SubTopic 25
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480238/815-25-50-1

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Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

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Amount of gain (loss) on derivative instrument designated and qualifying as fair value hedge included in assessment of hedge effectiveness, recognized in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480627/815-20-45-1A

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