Fair Value Option - Components of Gain (Loss) on Instruments at Fair Value and Related Derivatives (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020		Jun. 30, 2019
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Mark-to-market on related derivatives	$ 1,056	$ 497	$ (298)		$ 1,549
Gain (loss) on instruments designated at fair value and related derivatives	22	(17)	0		(26)
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	(1,087)	(522)	358	[1]	(1,603)	[1]
Credit risk component, total	5	0	(49)	[2],[3]	3	[3]
Total mark-to-market on financial instruments designated at fair value	(1,082)	(522)	309		(1,600)
Mark-to-market on related derivatives	1,096	496	(323)		1,555
Net realized gain on related long-term debt derivatives	8	9	14		19
Gain (loss) on instruments designated at fair value and related derivatives	22	(17)	0		(26)
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	0	0	0	[1]	0	[1]
Credit risk component, assets	5	0	(49)	[2],[3]	3	[3]
Total mark-to-market on financial instruments designated at fair value	5	0	(49)		3
Mark-to-market on related derivatives	0	0	37		0
Net realized gain on related long-term debt derivatives	0	0	0		0
Gain (loss) on instruments designated at fair value and related derivatives	5	0	(12)		3
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	2	(100)	(132)	[1]	(169)	[1]
Credit risk component, liabilities	0	0	0	[2],[3]	0	[3]
Total mark-to-market on financial instruments designated at fair value	2	(100)	(132)		(169)
Mark-to-market on related derivatives	0	83	150		136
Net realized gain on related long-term debt derivatives	8	9	14		19
Gain (loss) on instruments designated at fair value and related derivatives	10	(8)	32		(14)
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	(1,089)	(422)	490	[1]	(1,434)	[1]
Credit risk component, liabilities	0	0	0	[2],[3]	0	[3]
Total mark-to-market on financial instruments designated at fair value	(1,089)	(422)	490		(1,434)
Mark-to-market on related derivatives	1,096	413	(510)		1,419
Net realized gain on related long-term debt derivatives	0	0	0		0
Gain (loss) on instruments designated at fair value and related derivatives	$ 7	$ (9)	$ (20)		$ (15)

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

[2] During six months ended June 30, 2020, the loss in the credit risk component for loans and loans held for sale was attributable to the widening of credit spreads associated with certain commercial loans held for sale which were impacted by the COVID-19 pandemic.

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