Derivative Financial Instruments - Information about Fair Values of Derivative Instruments in Consolidated Balance Sheet (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	$ 324	$ 435
Liability Derivatives, Fair Value	943	1,355
Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	256	380
Liability Derivatives, Fair Value	898	1,300
Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	18	4
Liability Derivatives, Fair Value	10	9
Fair Value Hedges [Member] | Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	50	51
Liability Derivatives, Fair Value	35	46
Interest Rate Swap Agreements [Member] | Fair Value Hedges [Member] | Derivatives Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	12	1
Liability Derivatives, Fair Value	2	9
Commitments to Sell Real Estate Loans [Member] | Fair Value Hedges [Member] | Derivatives Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	6	3
Liability Derivatives, Fair Value	8
Commitments to Sell Real Estate Loans [Member] | Fair Value Hedges [Member] | Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	35	51
Liability Derivatives, Fair Value	3
Commitments to Originate Real Estate Loans for Sale [Member] | Fair Value Hedges [Member] | Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	15
Liability Derivatives, Fair Value	32	46
Interest Rate Contracts [Member] | Fair Value Hedges [Member] | Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	237	356
Liability Derivatives, Fair Value	879	1,278
Foreign Exchange and Other Option and Futures Contracts [Member] | Fair Value Hedges [Member] | Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	19	24
Liability Derivatives, Fair Value	$ 19	$ 22