Fair Value Option - Components of Gain (Loss) on Instruments at Fair Value and Related Derivatives (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Mark-to-market on related derivatives		$ 2,082	$ (1,131)	$ 1,136
Gain (loss) on instruments designated at fair value and related derivatives		(13)	19	43
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	[1]	(2,186)	1,135	(1,144)
Credit risk component, total	[2]	3	(4)	(2)
Total mark-to-market on financial instruments designated at fair value		(2,183)	1,131	(1,146)
Mark-to-market on related derivatives		2,131	(1,157)	1,132
Net realized gain on related long-term debt derivatives		39	45	57
Gain (loss) on instruments designated at fair value and related derivatives		(13)	19	43
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Loans [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	[1]	0	0	0
Credit risk component, assets	[2]	3	(4)	(2)
Total mark-to-market on financial instruments designated at fair value		3	(4)	(2)
Mark-to-market on related derivatives		0	0	0
Net realized gain on related long-term debt derivatives		0	0	0
Gain (loss) on instruments designated at fair value and related derivatives		3	(4)	(2)
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Securities purchased under resale agreements to Resell [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	[1]	0	0	(1)
Credit risk component, assets	[2]	0	0	0
Total mark-to-market on financial instruments designated at fair value		0	0	(1)
Mark-to-market on related derivatives		0	0	0
Net realized gain on related long-term debt derivatives		0	0	0
Gain (loss) on instruments designated at fair value and related derivatives		0	0	(1)
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Securities sold under repurchase agreements [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	[1]	0	1	2
Credit risk component, liabilities	[2]	0	0	0
Total mark-to-market on financial instruments designated at fair value		0	1	2
Mark-to-market on related derivatives		0	0	0
Net realized gain on related long-term debt derivatives		0	0	0
Gain (loss) on instruments designated at fair value and related derivatives		0	1	2
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Long-term debt [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	[1]	(200)	99	6
Credit risk component, liabilities	[2]	0	0	0
Total mark-to-market on financial instruments designated at fair value		(200)	99	6
Mark-to-market on related derivatives		148	(95)	(31)
Net realized gain on related long-term debt derivatives		39	45	57
Gain (loss) on instruments designated at fair value and related derivatives		(13)	49	32
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Hybrid Instrument [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	[1]	(1,986)	1,035	(1,151)
Credit risk component, liabilities	[2]	0	0	0
Total mark-to-market on financial instruments designated at fair value		(1,986)	1,035	(1,151)
Mark-to-market on related derivatives		1,983	(1,062)	1,163
Net realized gain on related long-term debt derivatives		0	0	0
Gain (loss) on instruments designated at fair value and related derivatives		$ (3)	$ (27)	$ 12

[1] As it relates to hybrid instruments, interest rate and other components primarily includes interest rate, foreign exchange and equity contract risks.

[2] The fair value movement on fair value option liabilities attributable to our own credit spread is recorded in other comprehensive income.