Derivative Financial Instruments - Impact of Derivatives on Balance Sheet (Detail) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Derivative Assets:
Derivative assets	$ 151	$ 224
Derivative Liabilities:
Derivative liabilities	(239)	(260)
Net total derivatives	(88)	(36)
Designated as Hedging Instrument [Member] | Fair Value [Member]
Derivative Assets:
Derivative assets	150	222
Derivative Liabilities:
Derivative liabilities	(226)	(190)
Net total derivatives	(76)	32
Trading [Member]
Derivative Assets:
Derivative assets	1	2
Derivative Liabilities:
Derivative liabilities	(13)	(70)
Net total derivatives	(12)	(68)
Interest Rate Swaps [Member]
Derivative Assets:
Derivative assets	151	224
Derivative Liabilities:
Derivative liabilities	(4)	(5)
Interest Rate Swaps [Member] | Designated as Hedging Instrument [Member] | Fair Value [Member]
Derivative Assets:
Derivative assets	150	222
Interest Rate Swaps [Member] | Trading [Member]
Derivative Assets:
Derivative assets	1	2
Derivative Liabilities:
Derivative liabilities	(4)	(5)
Cross-Currency Interest Rate Swaps [Member]
Derivative Liabilities:
Derivative liabilities	(226)	(190)
Cross-Currency Interest Rate Swaps [Member] | Designated as Hedging Instrument [Member] | Fair Value [Member]
Derivative Liabilities:
Derivative liabilities	(226)	(190)
Floor Income Contracts [Member]
Derivative Liabilities:
Derivative liabilities	(9)	(65)
Floor Income Contracts [Member] | Trading [Member]
Derivative Liabilities:
Derivative liabilities	$ (9)	$ (65)