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, 2020		Mar. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		$ 703		$ 2,088
Fair Value Assets, Gains (Losses) Included In Earnings		(45)		39
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income		5		2
Fair Value Assets, Purchases		0		0
Fair Value Assets, Issuances		0		0
Fair Value Assets, Settlements		16		(1,260)
Fair Value Assets, Transfers Into Level 3		0		0
Fair Value Assets, Transfers Out of Level 3		0		1
Fair Value Assets, Ending Balance		679		870
Fair Value Assets, Current Period Unrealized Gains (Losses) Included in Earnings		30		77	[1]
Fair Value Assets, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income , Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	[1]	5		2
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(1,128)		(1,337)
Fair Value Liability, Gains (Losses) Included In Earnings		6		(57)
Fair Value, Liability, Gains (Losses) Included in Other Comprehensive Income		28		(8)
Fair Value Liability, Purchases		0		0
Fair Value Liability, Issuances		(137)		(127)
Fair Value Liability, Settlements		170		58
Fair Value Liability, Transfers Into Level 3		0		0
Fair Value Liability, Transfers Out of Level 3		37		69
Fair Value Liability, Ending Balance		(1,024)		(1,402)
Fair Value Liability, Current Period Unrealized Gains (Losses) Included in Earnings		4		(149)	[2]
Fair Value Liability, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income	[2]	28		(8)
Interest rate contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[3]	10		2
Derivatives, net, Gains (Losses) included in Earnings	[3]	31		5
Derivatives, net, Gains (Losses) included in Other Comprehensive Income	[3]	0		0
Derivatives, net, Purchases	[3]	0		0
Derivatives, net, Issuances	[3]	0		0
Derivatives, net, Settlements	[3]	0		0
Derivatives, net, Transfers into Level 3	[3]	0		0
Derivatives, net, Transfers out of Level 3	[3]	0		0
Derivatives, net, Ending Balance	[3]	41		7
Derivatives, net, Current Period Unrealized Gains (Losses) Included in Earnings	[3]	31		5
Derivatives, net, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income	[3]	0		0
Foreign exchange contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[3]	(1)	[4]	(1)
Derivatives, net, Gains (Losses) included in Earnings	[3]	(2)		0
Derivatives, net, Gains (Losses) included in Other Comprehensive Income	[3]	0		0
Derivatives, net, Purchases	[3]	0		0
Derivatives, net, Issuances	[3]	0		0
Derivatives, net, Settlements	[3]	0		0
Derivatives, net, Transfers into Level 3	[3]	0		0
Derivatives, net, Transfers out of Level 3	[3]	0		0
Derivatives, net, Ending Balance	[3]	(3)	[4]	(1)
Derivatives, net, Current Period Unrealized Gains (Losses) Included in Earnings	[3]	(2)		0
Derivatives, net, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income	[3]	0		0
Equity contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[3]	72	[4]	(52)
Derivatives, net, Gains (Losses) included in Earnings	[3]	(74)		71
Derivatives, net, Gains (Losses) included in Other Comprehensive Income	[3]	0		0
Derivatives, net, Purchases	[3]	0		0
Derivatives, net, Issuances	[3]	0		0
Derivatives, net, Settlements	[3]	6		4
Derivatives, net, Transfers into Level 3	[3]	0		0
Derivatives, net, Transfers out of Level 3	[3]	0		1
Derivatives, net, Ending Balance	[3]	4	[4]	24
Derivatives, net, Current Period Unrealized Gains (Losses) Included in Earnings	[3]	12		75
Derivatives, net, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income	[3]	0		0
Credit contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[3]	59		52
Derivatives, net, Gains (Losses) included in Earnings	[3]	35		(37)
Derivatives, net, Gains (Losses) included in Other Comprehensive Income	[3]	0		0
Derivatives, net, Purchases	[3]	0		0
Derivatives, net, Issuances	[3]	0		0
Derivatives, net, Settlements	[3]	4		38
Derivatives, net, Transfers into Level 3	[3]	0		0
Derivatives, net, Transfers out of Level 3	[3]	0		0
Derivatives, net, Ending Balance	[3]	98		53
Derivatives, net, Current Period Unrealized Gains (Losses) Included in Earnings	[3]	35		0
Derivatives, net, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income	[3]	0		0
Other Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[3]	(75)		(35)
Derivatives, net, Gains (Losses) included in Earnings	[3]	11		(6)
Derivatives, net, Gains (Losses) included in Other Comprehensive Income	[3]	0		0
Derivatives, net, Purchases	[3]	0		0
Derivatives, net, Issuances	[3]	0		0
Derivatives, net, Settlements	[3]	6		4
Derivatives, net, Transfers into Level 3	[3]	0		0
Derivatives, net, Transfers out of Level 3	[3]	0		0
Derivatives, net, Ending Balance	[3]	(58)		(37)
Derivatives, net, Current Period Unrealized Gains (Losses) Included in Earnings	[3]	0		0
Derivatives, net, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income	[3]	0		0
Other assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[5]			4
Fair Value Assets, Gains (Losses) Included In Earnings	[5]			0
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[5]			0
Fair Value Assets, Purchases	[5]			0
Fair Value Assets, Issuances	[5]			0
Fair Value Assets, Settlements	[5]			0
Fair Value Assets, Transfers Into Level 3	[5]			0
Fair Value Assets, Transfers Out of Level 3	[5]			0
Fair Value Assets, Ending Balance	[5]			4
Fair Value Assets, Current Period Unrealized Gains (Losses) Included in Earnings	[1]			0
Fair Value Assets, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income , Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	[1]			0
Collateralized debt obligations [Member] | Trading assets, excluding derivatives [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]			100
Fair Value Assets, Gains (Losses) Included In Earnings	[1]			1
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[1]			0
Fair Value Assets, Purchases	[1]			0
Fair Value Assets, Issuances	[1]			0
Fair Value Assets, Settlements	[1]			(11)
Fair Value Assets, Transfers Into Level 3	[1]			0
Fair Value Assets, Transfers Out of Level 3	[1]			0
Fair Value Assets, Ending Balance	[1]			90
Fair Value Assets, Current Period Unrealized Gains (Losses) Included in Earnings	[1]			(6)
Fair Value Assets, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income , Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	[1]			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]
Fair Value Assets, Beginning Balance		17	[1]	16
Fair Value Assets, Gains (Losses) Included In Earnings	[1]	(1)		0
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income		0	[1]	0
Fair Value Assets, Purchases		0	[1]	0
Fair Value Assets, Issuances		0	[1]	0
Fair Value Assets, Settlements		0	[1]	0
Fair Value Assets, Transfers Into Level 3		0		0
Fair Value Assets, Transfers Out of Level 3		0	[1]	0
Fair Value Assets, Ending Balance		16	[1]	16
Fair Value Assets, Current Period Unrealized Gains (Losses) Included in Earnings	[1]	(1)		0
Fair Value Assets, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income , Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	[1]	0		0
Student loan asset-backed securities [Member] | Trading assets, excluding derivatives [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance				92
Fair Value Assets, Gains (Losses) Included In Earnings	[1]			5
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income				0
Fair Value Assets, Purchases				0
Fair Value Assets, Issuances				0
Fair Value Assets, Settlements				(2)
Fair Value Assets, Transfers Into Level 3				0
Fair Value Assets, Transfers Out of Level 3				0
Fair Value Assets, Ending Balance				95
Fair Value Assets, Current Period Unrealized Gains (Losses) Included in Earnings	[1]			3
Fair Value Assets, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income , Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	[1]			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]
Fair Value Assets, Beginning Balance		510		1,803	[1]
Fair Value Assets, Gains (Losses) Included In Earnings	[1]	(45)		0
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income		0		0	[1]
Fair Value Assets, Purchases		0		0	[1]
Fair Value Assets, Issuances		0		0	[1]
Fair Value Assets, Settlements		0		(1,293)	[1]
Fair Value Assets, Transfers Into Level 3		0		0	[1]
Fair Value Assets, Transfers Out of Level 3		0		0	[1]
Fair Value Assets, Ending Balance		465		510	[1]
Fair Value Assets, Current Period Unrealized Gains (Losses) Included in Earnings		(45)		0	[1]
Fair Value Assets, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income , Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	[1]	0		0
Other asset-backed securities available-for-sale [Member] | Available-for-sale securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[6]	111		107
Fair Value Assets, Gains (Losses) Included In Earnings	[6]	0		0
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[6]	5		2
Fair Value Assets, Purchases	[6]	0		0
Fair Value Assets, Issuances	[6]	0		0
Fair Value Assets, Settlements	[6]	0		0
Fair Value Assets, Transfers Into Level 3	[6]	0		0
Fair Value Assets, Transfers Out of Level 3	[6]	0		0
Fair Value Assets, Ending Balance	[6]	116		109
Fair Value Assets, Current Period Unrealized Gains (Losses) Included in Earnings		0	[6]	0	[1]
Fair Value Assets, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income , Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	[1]	5		2
Deposits [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance	[2]	(774)	[4],[7]	(925)
Fair Value Liability, Gains (Losses) Included In Earnings	[2]	1		(29)
Fair Value, Liability, Gains (Losses) Included in Other Comprehensive Income	[2]	18		(5)
Fair Value Liability, Purchases	[2]	0		0
Fair Value Liability, Issuances	[2]	(36)		(96)
Fair Value Liability, Settlements	[2]	105		45
Fair Value Liability, Transfers Into Level 3	[2]	0		0
Fair Value Liability, Transfers Out of Level 3	[2]	33		61
Fair Value Liability, Ending Balance	[2]	(653)	[4],[7]	(949)
Fair Value Liability, Current Period Unrealized Gains (Losses) Included in Earnings	[2]	0		(100)
Fair Value Liability, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income	[2]	18		(5)
Long-term debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance	[2]	(354)	[4],[7]	(412)
Fair Value Liability, Gains (Losses) Included In Earnings	[2]	5		(28)
Fair Value, Liability, Gains (Losses) Included in Other Comprehensive Income	[2]	10		(3)
Fair Value Liability, Purchases	[2]	0		0
Fair Value Liability, Issuances	[2]	(101)		(31)
Fair Value Liability, Settlements	[2]	65		13
Fair Value Liability, Transfers Into Level 3	[2]	0		0
Fair Value Liability, Transfers Out of Level 3	[2]	4		8
Fair Value Liability, Ending Balance	[2]	(371)	[4],[7]	(453)
Fair Value Liability, Current Period Unrealized Gains (Losses) Included in Earnings	[2]	4		(49)
Fair Value Liability, Current Period Unrealized Gains (Losses) Included in Other Comprehensive Income	[2]	$ 10		$ (3)

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

[2] 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 loss on instruments designated at fair value and related derivatives in the consolidated statement of income (loss).

[3] Level 3 net derivatives included derivative assets of $628 million and derivative liabilities of $546 million at March 31, 2020 and derivative assets of $288 million and derivative liabilities of $242 million at March 31, 2019. Gains (losses) on derivatives, net are predominantly included in trading revenue and loss on instruments designated at fair value and related derivatives in the consolidated statement of income (loss).

[4] 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.

[5] Represented contingent consideration receivable associated with the sale of a portion of our PB business, which concluded in 2019. Gains (losses) associated with this transaction were included in other income (loss) 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] 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.