Derivative Financial Instruments - Gains and Losses on Hedged Items in Fair Value Hedges (Detail) - Net interest income - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	$ (251)	$ 637	$ 57	$ 732
Gain (Loss) on Hedged Items	290	(615)	(20)	(634)
Asset-backed securities available-for-sale \| Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	(405)	735	67	927
Gain (Loss) on Hedged Items	617	(550)	504	(384)
Deposits \| Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	40	(15)	9	(42)
Gain (Loss) on Hedged Items	(53)	(20)	(92)	(58)
Long-term debt \| Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	114	(83)	(19)	(153)
Gain (Loss) on Hedged Items	$ (274)	$ (45)	$ (432)	$ (192)

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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- Definition

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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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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4E

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