Fair Value Measurements - Changes in Fair Value of Level 3 Assets and Liabilities (Detail) - Level 3 [Member] - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021		Mar. 31, 2020
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total assets, beginning balance		$ 319		$ 707
Assets, Total Realized/Unrealized Gains (Losses) Included in Earnings		(70)		(46)
Assets, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income		1		5
Assets, Purchases		0		0
Assets, Issuances		3		1
Assets, Settlements		(50)		16
Assets, Transfers Into Level 3		0		0
Assets, Transfers Out of Level 3		(1)		0
Total assets, ending balance		202		683
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Earnings		(70)		29	[1]
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income	[1]	1		5
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total liabilities, beginning balance		(1,094)		(1,128)
Total Realized/Unrealized Gains (Losses) Included in Earnings		1		6
Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income		0		28
Purchases		0		0
Issuances		(123)		(137)
Settlements		117		170
Transfers Into Level 3		(2)		0
Transfers Out of Level 3		16		37
Total liabilities, ending balance		(1,085)		(1,024)
Current Period Unrealized Gains (Losses) Still Held Included in Earnings		12		4
Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income		0		28
Interest rate contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[2]	34		10
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Earnings	[2]	(32)		31
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	[2]	0		0
Derivatives, net, Purchases	[2]	0		0
Derivatives, net, Issuances	[2]	0		0
Derivatives, net, Settlements	[2]	0		0
Derivatives, net, Transfers into Level 3	[2]	0		0
Derivatives, net, Transfers out of Level 3	[2]	0		0
Derivatives, net, Ending Balance	[2]	2		41
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	[2]	(17)		31
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income	[2]	0		0
Foreign exchange contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[2]	9	[3]	(1)
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Earnings	[2]	(11)		(2)
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	[2]	0		0
Derivatives, net, Purchases	[2]	0		0
Derivatives, net, Issuances	[2]	0		0
Derivatives, net, Settlements	[2]	0		0
Derivatives, net, Transfers into Level 3	[2]	0		0
Derivatives, net, Transfers out of Level 3	[2]	0		0
Derivatives, net, Ending Balance	[2]	(2)	[3]	(3)
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	[2]	(12)		(2)
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income	[2]	0		0
Equity contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[2]	119	[3]	72
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Earnings	[2]	(22)		(74)
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	[2]	0		0
Derivatives, net, Purchases	[2]	0		0
Derivatives, net, Issuances	[2]	0		0
Derivatives, net, Settlements	[2]	(54)		6
Derivatives, net, Transfers into Level 3	[2]	0		0
Derivatives, net, Transfers out of Level 3	[2]	(1)		0
Derivatives, net, Ending Balance	[2]	42	[3]	4
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	[2]	(32)		12
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income	[2]	0		0
Credit contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[2]	63		59
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Earnings	[2]	(17)		35
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	[2]	0		0
Derivatives, net, Purchases	[2]	0		0
Derivatives, net, Issuances	[2]	0		0
Derivatives, net, Settlements	[2]	(1)		4
Derivatives, net, Transfers into Level 3	[2]	0		0
Derivatives, net, Transfers out of Level 3	[2]	0		0
Derivatives, net, Ending Balance	[2]	45		98
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	[2]	(19)		35
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income	[2]	0		0
Other Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[2]	(59)		(75)	[4]
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Earnings	[2]	2		11	[4]
Derivatives, net, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	[2]	0		0	[4]
Derivatives, net, Purchases	[2]	0		0	[4]
Derivatives, net, Issuances	[2]	0		0	[4]
Derivatives, net, Settlements	[2]	7		6	[4]
Derivatives, net, Transfers into Level 3	[2]	0		0	[4]
Derivatives, net, Transfers out of Level 3	[2]	0		0	[4]
Derivatives, net, Ending Balance	[2]	(50)		(58)	[4]
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	[2]	0		0	[4]
Derivatives, net, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income	[2]	0		0	[4]
Mortgage Servicing Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total assets, beginning balance	[5]	7		4
Assets, Total Realized/Unrealized Gains (Losses) Included in Earnings	[5]	1		(1)
Assets, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	[5]	0		0
Assets, Purchases	[5]	0		0
Assets, Issuances	[5]	3		1
Assets, Settlements	[5]	0		0
Assets, Transfers Into Level 3	[5]	0		0
Assets, Transfers Out of Level 3	[5]	0		0
Total assets, ending balance	[5]	11		4
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	[5]	1		(1)
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income	[5]	0		0
Residential mortgage asset-backed securities [Member] | Trading assets, excluding derivatives [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total assets, beginning balance	[1]	15		17
Assets, Total Realized/Unrealized Gains (Losses) Included in Earnings	[1]	9		(1)
Assets, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	[1]	0		0
Assets, Purchases	[1]	0		0
Assets, Issuances	[1]	0		0
Assets, Settlements	[1]	0		0
Assets, Transfers Into Level 3		0		0	[1]
Assets, Transfers Out of Level 3	[1]	0		0
Total assets, ending balance	[1]	24		16
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	[1]	9		(1)
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income	[1]	0		0
Corporate and other domestic debt securities [Member] | Trading assets, excluding derivatives [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total assets, beginning balance	[1]			510
Assets, Total Realized/Unrealized Gains (Losses) Included in Earnings	[1]			(45)
Assets, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	[1]			0
Assets, Purchases	[1]			0
Assets, Issuances	[1]			0
Assets, Settlements	[1]			0
Assets, Transfers Into Level 3	[1]			0
Assets, Transfers Out of Level 3	[1]			0
Total assets, ending balance	[1]			465
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	[1]			(45)
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income	[1]			0
Other [Member] | Available-for-sale securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total assets, beginning balance	[6]	131		111
Assets, Total Realized/Unrealized Gains (Losses) Included in Earnings	[6]	0		0
Assets, Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	[6]	1		5
Assets, Purchases	[6]	0		0
Assets, Issuances	[6]	0		0
Assets, Settlements	[6]	(2)		0
Assets, Transfers Into Level 3	[6]	0		0
Assets, Transfers Out of Level 3	[6]	0		0
Total assets, ending balance	[6]	130		116
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Earnings	[6]	0		0
Assets, Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income	[6]	1		5
Domestic Deposits [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total liabilities, beginning balance	[7]	(646)	[3],[8]	(774)
Total Realized/Unrealized Gains (Losses) Included in Earnings	[7]	4		1
Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	[7]	0		18
Purchases	[7]	0		0
Issuances	[7]	0		(36)
Settlements	[7]	28		105
Transfers Into Level 3	[7]	0		0
Transfers Out of Level 3	[7]	15		33
Total liabilities, ending balance	[7]	(599)	[3],[8]	(653)
Current Period Unrealized Gains (Losses) Still Held Included in Earnings	[7]	8		0
Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income	[7]	0		18
Long-term debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total liabilities, beginning balance	[7]	(448)	[3],[8]	(354)
Total Realized/Unrealized Gains (Losses) Included in Earnings	[7]	(3)		5
Total Realized/Unrealized Gains (Losses) Included in Other Comprehensive Income	[7]	0		10
Purchases	[7]	0		0
Issuances	[7]	(123)		(101)
Settlements	[7]	89		65
Transfers Into Level 3	[7]	(2)		0
Transfers Out of Level 3	[7]	1		4
Total liabilities, ending balance	[7]	(486)	[3],[8]	(371)
Current Period Unrealized Gains (Losses) Still Held Included in Earnings	[7]	4		4
Current Period Unrealized Gains (Losses) Still Held Included in Other Comprehensive Income	[7]	$ 0		$ 10

[1] Gains (losses) on trading assets, excluding derivatives are included in trading revenue in the consolidated statement of income (loss).

[2] Level 3 net derivatives included derivative assets of $541 million and derivative liabilities of $504 million at March 31, 2021 and derivative assets of $628 million and derivative liabilities of $546 million at March 31, 2020. Gains (losses) on derivatives, net are predominantly included in trading revenue and gain (loss) on instruments designated at fair value and related derivatives in the consolidated statement of income (loss).

[3] We are the client-facing entity and we enter into identical but opposite derivatives to transfer the resultant risks to our affiliates. With the exception of counterparty credit risks, we are market neutral. The corresponding intra-group derivatives are presented as equity derivatives and foreign exchange derivatives in the table.

[4] Consists of swap agreements entered into in conjunction with the sales of Visa Class B Shares. Gains (losses) on these swap agreements are included in other income in the consolidated statement of income (loss).

[5] Gain (losses) on mortgage servicing rights are included in other income in the consolidated statement of income (loss).

[6] Realized gains (losses) on securities available-for-sale are included in other securities gains, net in the consolidated statement of income (loss). Changes in the allowance for credit losses on securities available-for-sale are included in the provision for credit losses in the consolidated statement of income (loss). Unrealized gains (losses) on securities available-for-sale are included in other comprehensive income.

[7] Excluding unrealized gains (losses) on fair value option liabilities attributable to our own credit spread, which are recorded in other comprehensive income, gains (losses) on fair value option liabilities are included in gain (loss) on instruments designated at fair value and related derivatives in the consolidated statement of income (loss).

[8] Structured deposits and structured notes contain embedded derivative features whose fair value measurements contain significant Level 3 inputs. See equity and foreign exchange derivatives below for a discussion of the uncertainty of Level 3 inputs related to structured deposits and structured notes.