Derivative Financial Instruments - Information about Fair Values of Derivative Instruments in Consolidated Balance Sheet (Detail) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Derivatives, Fair Value [Line Items]
Asset derivatives, fair value	$ 295	$ 324
Liability derivatives, fair value	1,041	943
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Asset derivatives, fair value	3	18
Liability derivatives, fair value	14	10
Fair value hedges:
Derivatives, Fair Value [Line Items]
Asset derivatives, fair value	245	256
Liability derivatives, fair value	992	898
Fair value hedges: | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Asset derivatives, fair value	47	50
Liability derivatives, fair value	35	35
Interest rate swap agreements | Fair value hedges: | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Asset derivatives, fair value	2	12
Liability derivatives, fair value	12	2
Commitments to sell real estate loans | Fair value hedges: | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Asset derivatives, fair value	1	6
Liability derivatives, fair value	2	8
Commitments to sell real estate loans | Fair value hedges: | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Asset derivatives, fair value	32	35
Liability derivatives, fair value	6	3
Mortgage-related commitments to originate real estate loans for sale | Fair value hedges: | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Asset derivatives, fair value	15	15
Liability derivatives, fair value	29	32
Interest Rate Contracts | Fair value hedges: | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Asset derivatives, fair value	232	237
Liability derivatives, fair value	982	879
Foreign exchange and other option and futures contracts | Fair value hedges: | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Asset derivatives, fair value	13	19
Liability derivatives, fair value	$ 10	$ 19