Fair Value Option - Components of Gain (Loss) on Instruments at Fair Value and Related Derivatives (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Mark-to-market on related derivatives	$ 826	$ (1,493)	$ 1,055
Gain (loss) on instruments designated at fair value and related derivatives	(42)	(50)	35
Gain (loss) on instruments designated at fair value and related derivatives
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	(984)	1,487	(1,045)
Credit risk component, total	11	(85)	2
Total mark-to-market on financial instruments designated at fair value	(973)	1,402	(1,043)
Mark-to-market on related derivatives	932	(1,478)	1,040
Net realized gain (loss) on related long-term debt derivatives	(1)	26	38
Gain (loss) on instruments designated at fair value and related derivatives	(42)	(50)	35
Gain (loss) on instruments designated at fair value and related derivatives | Loans
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	0	0	0
Credit risk component, assets	11	(85)	2
Total mark-to-market on financial instruments designated at fair value	11	(85)	2
Mark-to-market on related derivatives	0	0	0
Net realized gain (loss) on related long-term debt derivatives	0	0	0
Gain (loss) on instruments designated at fair value and related derivatives	11	(85)	2
Gain (loss) on instruments designated at fair value and related derivatives | Long-term debt
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	3	197	74
Credit risk component, liabilities	0	0	0
Total mark-to-market on financial instruments designated at fair value	3	197	74
Mark-to-market on related derivatives	(4)	(221)	(88)
Net realized gain (loss) on related long-term debt derivatives	(1)	26	38
Gain (loss) on instruments designated at fair value and related derivatives	(2)	2	24
Gain (loss) on instruments designated at fair value and related derivatives | Hybrid Instruments
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	(987)	1,290	(1,119)
Credit risk component, liabilities	0	0	0
Total mark-to-market on financial instruments designated at fair value	(987)	1,290	(1,119)
Mark-to-market on related derivatives	936	(1,257)	1,128
Net realized gain (loss) on related long-term debt derivatives	0	0	0
Gain (loss) on instruments designated at fair value and related derivatives	$ (51)	$ 33	$ 9