Fair Value Measurements - Changes in Fair Value of Level 3 Assets and Liabilities (Detail) - Level 3 [Member] - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019		Jun. 30, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		$ 867		$ 2,152		$ 2,088		$ 2,207
Fair Value Assets, Gains (Losses) Included In Earnings		43		(24)		82		(58)
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income		4		0		6		(4)
Fair Value Assets, Purchases		0		0		0		0
Fair Value Assets, Issuances		0		0		0		0
Fair Value Assets, Settlements		(9)		(16)		(1,272)		(33)
Fair Value Assets, Transfers Into Level 3		0		(1)		0		(1)
Fair Value Assets, Transfers Out of Level 3		(7)		2		(6)		2
Fair Value Assets, Ending Balance		898		2,113		898		2,113
Fair Value Assets, Current Period Unrealized Gains (Losses)		36		(10)		115		(46)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(1,402)		(1,546)		(1,337)		(1,538)
Fair Value Liability, Gains (Losses) Included In Earnings		(50)		(3)		(107)		29
Fair Value, Liability, Gains (Losses) Included in Other Comprehensive Income		3		6		(5)		8
Fair Value Liability, Purchases		0		0		0		0
Fair Value Liability, Issuances		(82)		(116)		(209)		(322)
Fair Value Liability, Settlements		84		112		142		201
Fair Value Liability, Transfers Into Level 3		(5)		(10)		(5)		(13)
Fair Value Liability, Transfers Out of Level 3		81		124		150		202
Fair Value Liability, Ending Balance		(1,371)		(1,433)		(1,371)		(1,433)
Fair Value Liability, Current Period Unrealized Gains (Losses)		(39)		9		(196)		43
Interest rate contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[1]	7				2
Derivatives, net, Gains (Losses) included in Earnings	[1]	8				13
Derivatives, net, Gains (Losses) included in Other Comprehensive Income	[1]	0				0
Derivatives, net, Purchases	[1]	0				0
Derivatives, net, Issuances	[1]	0				0
Derivatives, net, Settlements	[1]	0				0
Derivatives, net, Transfers into Level 3	[1]	0				0
Derivatives, net, Transfers out of Level 3	[1]	(5)				(5)
Derivatives, net, Ending Balance	[1]	10				10
Derivatives, net, Current Period Unrealized Gains (Losses)	[1]	3				8
Foreign exchange contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[1]	(1)		0		(1)	[2]	0
Derivatives, net, Gains (Losses) included in Earnings	[1]	0		(1)		0		(1)
Derivatives, net, Gains (Losses) included in Other Comprehensive Income	[1]	0		0		0		0
Derivatives, net, Purchases	[1]	0		0		0		0
Derivatives, net, Issuances	[1]	0		0		0		0
Derivatives, net, Settlements	[1]	0		0		0		0
Derivatives, net, Transfers into Level 3	[1]	0		0		0		0
Derivatives, net, Transfers out of Level 3	[1]	0		0		0		0
Derivatives, net, Ending Balance	[1]	(1)	[2]	(1)		(1)	[2]	(1)
Derivatives, net, Current Period Unrealized Gains (Losses)	[1]	0		(1)		0		(1)
Equity contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[1]	24		27		(52)	[2]	81
Derivatives, net, Gains (Losses) included in Earnings	[1]	39		(10)		110		(50)
Derivatives, net, Gains (Losses) included in Other Comprehensive Income	[1]	0		0		0		0
Derivatives, net, Purchases	[1]	0		0		0		0
Derivatives, net, Issuances	[1]	0		0		0		0
Derivatives, net, Settlements	[1]	1		(16)		5		(30)
Derivatives, net, Transfers into Level 3	[1]	0		(1)		0		(1)
Derivatives, net, Transfers out of Level 3	[1]	(2)		2		(1)		2
Derivatives, net, Ending Balance	[1]	62	[2]	2		62	[2]	2
Derivatives, net, Current Period Unrealized Gains (Losses)	[1]	40		(7)		115		(45)
Credit contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[1]	53		113		52		114
Derivatives, net, Gains (Losses) included in Earnings	[1]	(3)		1		(40)		2
Derivatives, net, Gains (Losses) included in Other Comprehensive Income	[1]	0		0		0		0
Derivatives, net, Purchases	[1]	0		0		0		0
Derivatives, net, Issuances	[1]	0		0		0		0
Derivatives, net, Settlements	[1]	(4)		(4)		34		(6)
Derivatives, net, Transfers into Level 3	[1]	0		0		0		0
Derivatives, net, Transfers out of Level 3	[1]	0		0		0		0
Derivatives, net, Ending Balance	[1]	46		110		46		110
Derivatives, net, Current Period Unrealized Gains (Losses)	[1]	(2)		(3)		(2)		(4)
Other Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivatives, net, Beginning Balance	[1]	(37)		(44)		(35)		(46)
Derivatives, net, Gains (Losses) included in Earnings	[1]	(3)		(12)		(9)		(14)
Derivatives, net, Gains (Losses) included in Other Comprehensive Income	[1]	0		0		0		0
Derivatives, net, Purchases	[1]	0		0		0		0
Derivatives, net, Issuances	[1]	0		0		0		0
Derivatives, net, Settlements	[1]	5		5		9		9
Derivatives, net, Transfers into Level 3	[1]	0		0		0		0
Derivatives, net, Transfers out of Level 3	[1]	0		0		0		0
Derivatives, net, Ending Balance	[1]	(35)		(51)		(35)		(51)
Derivatives, net, Current Period Unrealized Gains (Losses)	[1]	0		0		0		0
Domestic Deposits [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance	[3]	(949)		(916)		(925)	[2],[4]	(897)
Fair Value Liability, Gains (Losses) Included In Earnings	[3]	(35)		2		(64)		23
Fair Value, Liability, Gains (Losses) Included in Other Comprehensive Income	[3]	2		5		(3)		3
Fair Value Liability, Purchases	[3]	0		0		0		0
Fair Value Liability, Issuances	[3]	(49)		(88)		(145)		(179)
Fair Value Liability, Settlements	[3]	64		38		109		60
Fair Value Liability, Transfers Into Level 3	[3]	(5)		(10)		(5)		(13)
Fair Value Liability, Transfers Out of Level 3	[3]	42		93		103		127
Fair Value Liability, Ending Balance	[3]	(930)	[2],[4]	(876)		(930)	[2],[4]	(876)
Fair Value Liability, Current Period Unrealized Gains (Losses)	[3]	(30)		8		(135)		25
Long-term debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance	[3]	(453)		(630)		(412)	[2],[4]	(641)
Fair Value Liability, Gains (Losses) Included In Earnings	[3]	(15)		(5)		(43)		6
Fair Value, Liability, Gains (Losses) Included in Other Comprehensive Income	[3]	1		1		(2)		5
Fair Value Liability, Purchases	[3]	0		0		0		0
Fair Value Liability, Issuances	[3]	(33)		(28)		(64)		(143)
Fair Value Liability, Settlements	[3]	20		74		33		141
Fair Value Liability, Transfers Into Level 3	[3]	0		0		0		0
Fair Value Liability, Transfers Out of Level 3	[3]	39		31		47		75
Fair Value Liability, Ending Balance	[3]	(441)	[2],[4]	(557)		(441)	[2],[4]	(557)
Fair Value Liability, Current Period Unrealized Gains (Losses)	[3]	(9)		1		(61)		18
Trading assets, excluding derivatives [Member] | Collateralized debt obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[5]	90		131		100		129
Fair Value Assets, Gains (Losses) Included In Earnings	[5]	2		1		3		8
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[5]	0		0		0		0
Fair Value Assets, Purchases	[5]	0		0		0		0
Fair Value Assets, Issuances	[5]	0		0		0		0
Fair Value Assets, Settlements	[5]	(6)		(1)		(17)		(6)
Fair Value Assets, Transfers Into Level 3	[5]	0		0		0		0
Fair Value Assets, Transfers Out of Level 3	[5]	0		0		0		0
Fair Value Assets, Ending Balance	[5]	86		131		86		131
Fair Value Assets, Current Period Unrealized Gains (Losses)	[5]	(4)		1		(10)		8
Trading assets, excluding derivatives [Member] | Residential mortgage asset-backed securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		16				16	[5]
Fair Value Assets, Gains (Losses) Included In Earnings		0				0	[5]
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[5]	0				0
Fair Value Assets, Purchases		0				0	[5]
Fair Value Assets, Issuances		0				0	[5]
Fair Value Assets, Settlements		0				0	[5]
Fair Value Assets, Transfers Into Level 3		0				0
Fair Value Assets, Transfers Out of Level 3		0				0	[5]
Fair Value Assets, Ending Balance	[5]	16				16
Fair Value Assets, Current Period Unrealized Gains (Losses)		0				0	[5]
Trading assets, excluding derivatives [Member] | Student loan asset-backed securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		95				92
Fair Value Assets, Gains (Losses) Included In Earnings		0				5	[5]
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income		0	[5]			0
Fair Value Assets, Purchases		0				0
Fair Value Assets, Issuances		0				0
Fair Value Assets, Settlements		(5)				(7)
Fair Value Assets, Transfers Into Level 3		0				0
Fair Value Assets, Transfers Out of Level 3		0				0
Fair Value Assets, Ending Balance		90				90
Fair Value Assets, Current Period Unrealized Gains (Losses)		(5)				(2)
Trading assets, excluding derivatives [Member] | Corporate and other domestic debt securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		510	[5]	1,803	[5]	1,803		1,803	[5]
Fair Value Assets, Gains (Losses) Included In Earnings	[5]	0		0		0		0
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income		0	[5]	0	[5]	0		0	[5]
Fair Value Assets, Purchases		0	[5]	0	[5]	0		0	[5]
Fair Value Assets, Issuances		0	[5]	0	[5]	0		0	[5]
Fair Value Assets, Settlements		0	[5]	0	[5]	(1,293)		0	[5]
Fair Value Assets, Transfers Into Level 3		0	[5]	0	[5]	0		0	[5]
Fair Value Assets, Transfers Out of Level 3		0	[5]	0	[5]	0		0	[5]
Fair Value Assets, Ending Balance	[5]	510		1,803		510		1,803
Fair Value Assets, Current Period Unrealized Gains (Losses)		0	[5]	0	[5]	0		0	[5]
Available-for-sale securities [Member] | Other asset-backed securities available-for-sale [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[6]	109		107		107		111
Fair Value Assets, Gains (Losses) Included In Earnings	[6]	0		0		0		0
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income		4	[6]	0	[1]	6	[6]	(4)	[6]
Fair Value Assets, Purchases	[6]	0		0		0		0
Fair Value Assets, Issuances	[6]	0		0		0		0
Fair Value Assets, Settlements	[6]	0		0		0		0
Fair Value Assets, Transfers Into Level 3	[6]	0		0		0		0
Fair Value Assets, Transfers Out of Level 3	[6]	0		0		0		0
Fair Value Assets, Ending Balance	[6]	113		107		113		107
Fair Value Assets, Current Period Unrealized Gains (Losses)	[6]	4		0		6		(4)
Other assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[7]	1		15		4		15
Fair Value Assets, Gains (Losses) Included In Earnings	[7]	0		(3)		0		(3)
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[7]	0		0		0		0
Fair Value Assets, Purchases	[7]	0		0		0		0
Fair Value Assets, Issuances	[7]	0		0		0		0
Fair Value Assets, Settlements	[7]	0		0		(3)		0
Fair Value Assets, Transfers Into Level 3	[7]	0		0		0		0
Fair Value Assets, Transfers Out of Level 3	[7]	0		0		0		0
Fair Value Assets, Ending Balance	[7]	1		12		1		12
Fair Value Assets, Current Period Unrealized Gains (Losses)	[7]	$ 0		$ 0		$ 0		$ 0

[1] Level 3 net derivatives included derivative assets of $276 million and derivative liabilities of $194 million at June 30, 2019 and derivative assets of $253 million and derivative liabilities of $193 million at June 30, 2018. 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.

[2] 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.

[3] Excluding unrealized gains (losses) on fair value option liabilities attributable to our own credit spread, which are recorded in other comprehensive income (loss), 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.

[4] Structured deposits and structured notes contain embedded derivative features whose fair value measurements contain significant Level 3 inputs.

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

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

[7] Represents contingent consideration receivable associated with the sale of a portion of our PB business. Gains (losses) associated with this transaction are included in other income (loss) in the consolidated statement of income.