Derivative Financial Instruments - Mark-to-Market Impact of Derivatives on Statements of Income (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Mark-to-market gains (losses) recognized	$ 98	$ 36
Interest Expense and Derivative Instruments Hedging Activities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Mark-to-market gains (losses) recognized	139	81
Designated as Hedging Instrument [Member] \| Fair Value [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Mark-to-market gains (losses) recognized	41	45
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	(288)	(197)
Gains (losses) recognized in net income on hedged items	313	212
Net fair value hedge ineffectiveness gains (losses)	25	15
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	(36)	70
Gains (losses) recognized in net income on hedged items	52	(40)
Net fair value hedge ineffectiveness gains (losses)	16	30
Trading [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Mark-to-market gains (losses) recognized	98	36
Trading [Member] \| Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Mark-to-market gains (losses) recognized	62	22
Trading [Member] \| Floor Income Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Mark-to-market gains (losses) recognized	$ 36	$ 14

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.

+ References

No definition available.

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (d)
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Amount of gain (loss) from the ineffectiveness of the hedge.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

+ References

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-Publisher FASB
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