Derivative Financial Instruments - Mark-to-Market Impact of Derivatives on Statements of Income (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Derivative Instruments Gain Loss [Line Items]
Mark-to-market gains (losses) recognized	$ 11	$ 171	$ 64
Interest Expense and Derivative Instruments Hedging Activities [Member]
Derivative Instruments Gain Loss [Line Items]
Mark-to-market gains (losses) recognized	(35)	254	152
Designated as Hedging Instrument [Member] \| Fair Value [Member]
Derivative Instruments Gain Loss [Line Items]
Mark-to-market gains (losses) recognized	(46)	83	88
Designated as Hedging Instrument [Member] \| Fair Value [Member] \| Interest Rate Swaps [Member]
Derivative Instruments Gain Loss [Line Items]
Gains (losses) recognized in net income on derivatives	104	(610)	(310)
Gains (losses) recognized in net income on hedged items	(86)	96	(55)
Net fair value hedge ineffectiveness gains (losses)	(24)	50	39
Designated as Hedging Instrument [Member] \| Fair Value [Member] \| Cross-Currency Interest Rate Swaps [Member]
Derivative Instruments Gain Loss [Line Items]
Gains (losses) recognized in net income on derivatives	64	(63)	104
Gains (losses) recognized in net income on hedged items	(128)	660	349
Net fair value hedge ineffectiveness gains (losses)	(22)	33	49
Designated as Hedging Instrument [Member] \| Cash Flow [Member]
Derivative Instruments Gain Loss [Line Items]
Mark-to-market gains (losses) recognized	0	0	0
Trading [Member]
Derivative Instruments Gain Loss [Line Items]
Mark-to-market gains (losses) recognized	11	171	64
Trading [Member] \| Interest Rate Swaps [Member]
Derivative Instruments Gain Loss [Line Items]
Mark-to-market gains (losses) recognized	11	130	30
Trading [Member] \| Floor Income Contracts [Member]
Derivative Instruments Gain Loss [Line Items]
Mark-to-market gains (losses) recognized	$ 0	$ 41	$ 34

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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The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

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Amount of gain (loss) from the ineffectiveness of the hedge.

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