Fair Value Measurements - Changes in Fair Value of Level 3 Assets and Liabilities (Detail) - Level 3 [Member] - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2017		Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		$ 2,172		$ 3,358		$ 3,356		$ 3,328
Fair Value Assets, Gains (Losses) Included In Earnings		43		32		95		70
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income		0		0		0		0
Fair Value Assets, Purchases		0		4		0		14
Fair Value Assets, Issuances		0		0		(35)		0
Fair Value Assets, Settlements		(35)		(13)		(1,239)		(32)
Fair Value Assets, Transfers Into Level 3		0		(1)		0		0
Fair Value Assets, Transfers Out of Level 3		(2)		(92)		1		(92)
Fair Value Assets, Ending Balance		2,178		3,288		2,178		3,288
Fair Value Assets, Current Period Unrealized Gains (Losses)		42		(4)		59		31
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(1,683)		(2,250)		(1,906)		(2,613)
Fair Value Liability, Gains (Losses) Included In Earnings		(41)		(34)		(95)		(97)
Fair Value, Liability, Gains (Losses) Included in Other Comprehensive Income		(4)		0		2		0
Fair Value Liability, Purchases		0		0		0		0
Fair Value Liability, Issuances		(94)		(128)		(307)		(422)
Fair Value Liability, Settlements		219		410		574		858
Fair Value Liability, Transfers Into Level 3		(4)		(39)		(27)		(54)
Fair Value Liability, Transfers Out of Level 3		109		124		261		411
Fair Value Liability, Ending Balance		(1,498)		(1,917)		(1,498)		(1,917)
Fair Value Liability, Current Period Unrealized Gains (Losses)		(38)		(68)		(74)		(69)
Interest rate contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	0		1		1		1
Fair Value Assets, Gains (Losses) Included In Earnings	[1]	0		0		(1)		0
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[1]	0		0		0		0
Fair Value Assets, Purchases	[1]	0		0		0		0
Fair Value Assets, Issuances	[1]	0		0		0		0
Fair Value Assets, Settlements	[1]	0		0		0		0
Fair Value Assets, Transfers Into Level 3	[1]	0		0		0		0
Fair Value Assets, Transfers Out of Level 3	[1]	0		0		0		0
Fair Value Assets, Ending Balance	[1]	0		1		0		1
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	0		0		(1)		0
Foreign exchange contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	0		0		0		0
Fair Value Assets, Gains (Losses) Included In Earnings	[1]	0		0		0		0
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[1]	0		0		0		0
Fair Value Assets, Purchases	[1]	0		0		0		0
Fair Value Assets, Issuances	[1]	0		0		0		0
Fair Value Assets, Settlements	[1]	0		0		0		0
Fair Value Assets, Transfers Into Level 3	[1]	0		0		0		0
Fair Value Assets, Transfers Out of Level 3	[1]	0		0		0		0
Fair Value Assets, Ending Balance	[1]	0		0		0		0
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	0		0		0		0
Equity contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	32		(15)		(2)		(83)
Fair Value Assets, Gains (Losses) Included In Earnings	[1]	33		20		72		75
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[1]	0		0		0		0
Fair Value Assets, Purchases	[1]	0		0		0		0
Fair Value Assets, Issuances	[1]	0		0		0		0
Fair Value Assets, Settlements	[1]	(7)		(2)		(15)		10
Fair Value Assets, Transfers Into Level 3	[1]	0		(1)		0		0
Fair Value Assets, Transfers Out of Level 3	[1]	(2)		3		1		3
Fair Value Assets, Ending Balance	[1]	56		5		56		5
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	26		0		52		50
Credit contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	143		188		193		179
Fair Value Assets, Gains (Losses) Included In Earnings	[1]	(5)		11		(9)		27
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[1]	0		0		0		0
Fair Value Assets, Purchases	[1]	0		0		0		0
Fair Value Assets, Issuances	[1]	0		0		0		0
Fair Value Assets, Settlements	[1]	(23)		8		(69)		1
Fair Value Assets, Transfers Into Level 3	[1]	0		0		0		0
Fair Value Assets, Transfers Out of Level 3	[1]	0		0		0		0
Fair Value Assets, Ending Balance	[1]	115		207		115		207
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	(2)		(3)		(18)		18
Other Contract [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1],[2]	(44)				(9)
Fair Value Assets, Gains (Losses) Included In Earnings	[1],[2]	(5)				(7)
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[1],[2]	0				0
Fair Value Assets, Purchases	[1],[2]	0				0
Fair Value Assets, Issuances	[1],[2]	0				(35)
Fair Value Assets, Settlements	[1],[2]	3				5
Fair Value Assets, Transfers Into Level 3	[1],[2]	0				0
Fair Value Assets, Transfers Out of Level 3	[1],[2]	0				0
Fair Value Assets, Ending Balance	[1],[2]	(46)				(46)
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1],[2]	0				0
Collateralized debt obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		131	[3]	201	[3]	184	[3]	221	[4]
Fair Value Assets, Gains (Losses) Included In Earnings	[3]	2		4		20		(4)
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income		0	[3]	0	[3]	0	[3]	0	[4]
Fair Value Assets, Purchases		0	[3]	0	[3]	0	[3]	0	[4]
Fair Value Assets, Issuances		0	[3]	0	[3]	0	[3]	0	[4]
Fair Value Assets, Settlements		(8)	[3]	(14)	[3]	(79)	[3]	(26)	[4]
Fair Value Assets, Transfers Into Level 3		0	[3]	0	[3]	0	[3]	0	[4]
Fair Value Assets, Transfers Out of Level 3		0	[3]	0	[3]	0	[3]	0	[4]
Fair Value Assets, Ending Balance	[3]	125		191	[4]	125		191	[4]
Fair Value Assets, Current Period Unrealized Gains (Losses)		1	[3]	2	[3]	6	[3]	(9)	[4]
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		1,803	[3]	2,879	[3]	2,884	[3]	2,870	[4]
Fair Value Assets, Gains (Losses) Included In Earnings	[3]	0		1		0		0
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income		0	[3]	0	[3]	0	[3]	0	[4]
Fair Value Assets, Purchases		0	[3]	4	[3]	0	[3]	14	[4]
Fair Value Assets, Issuances		0	[3]	0	[3]	0	[3]	0	[4]
Fair Value Assets, Settlements		0	[3]	0	[3]	(1,081)	[3]	0	[4]
Fair Value Assets, Transfers Into Level 3		0	[3]	0	[3]	0	[3]	0	[4]
Fair Value Assets, Transfers Out of Level 3		0	[3]	0	[3]	0	[3]	0	[4]
Fair Value Assets, Ending Balance	[3]	1,803		2,884	[4]	1,803		2,884	[4]
Fair Value Assets, Current Period Unrealized Gains (Losses)		0	[3]	1	[3]	0	[3]	0	[4]
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	[5]	107				105
Fair Value Assets, Gains (Losses) Included In Earnings	[5]	3				5
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[5]	0				0
Fair Value Assets, Purchases		0	[5]			0	[1]
Fair Value Assets, Issuances		0	[5]			0	[1]
Fair Value Assets, Settlements		0	[5]			0	[1]
Fair Value Assets, Transfers Into Level 3		0	[5]			0	[1]
Fair Value Assets, Transfers Out of Level 3		0	[5]			0	[1]
Fair Value Assets, Ending Balance	[1],[5]	110				110
Fair Value Assets, Current Period Unrealized Gains (Losses)		2	[5]			5	[1]
Mortgage servicing rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[5],[6]			104				140
Fair Value Assets, Gains (Losses) Included In Earnings	[5],[6]			(4)				(28)
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[1],[6]			0				0
Fair Value Assets, Purchases	[5],[6]			0				0
Fair Value Assets, Issuances	[5],[6]			0				0
Fair Value Assets, Settlements	[5],[6]			(5)				(17)
Fair Value Assets, Transfers Into Level 3	[5],[6]			0				0
Fair Value Assets, Transfers Out of Level 3	[5],[6]			(95)				(95)
Fair Value Assets, Ending Balance	[5],[6]			0				0
Fair Value Assets, Current Period Unrealized Gains (Losses)	[5],[6]			(4)				(28)
Domestic Deposits [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance	[7]	(1,142)		(1,677)		(1,407)		(1,867)
Fair Value Liability, Gains (Losses) Included In Earnings	[7]	(19)		(3)		(33)		(74)
Fair Value, Liability, Gains (Losses) Included in Other Comprehensive Income	[7]	(3)		0		9		0
Fair Value Liability, Purchases	[7]	0		0		0		0
Fair Value Liability, Issuances	[7]	(50)		(42)		(141)		(206)
Fair Value Liability, Settlements	[7]	191		300		468		599
Fair Value Liability, Transfers Into Level 3	[7]	(4)		(39)		(25)		(54)
Fair Value Liability, Transfers Out of Level 3	[7]	82		57		184		198
Fair Value Liability, Ending Balance	[7]	(945)		(1,404)		(945)		(1,404)
Fair Value Liability, Current Period Unrealized Gains (Losses)	[7]	(17)		(26)		(18)		(46)
Long-term debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance	[7]	(541)		(573)		(499)		(746)
Fair Value Liability, Gains (Losses) Included In Earnings	[7]	(22)		(31)		(62)		(23)
Fair Value, Liability, Gains (Losses) Included in Other Comprehensive Income	[7]	(1)		0		(7)		0
Fair Value Liability, Purchases	[7]	0		0		0		0
Fair Value Liability, Issuances	[7]	(44)		(86)		(166)		(216)
Fair Value Liability, Settlements	[7]	28		110		106		259
Fair Value Liability, Transfers Into Level 3	[7]	0		0		(2)		0
Fair Value Liability, Transfers Out of Level 3	[7]	27		67		77		213
Fair Value Liability, Ending Balance	[7]	(553)		(513)		(553)		(513)
Fair Value Liability, Current Period Unrealized Gains (Losses)	[7]	(21)		$ (42)		(56)		$ (23)
Other assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[8]	0				0
Fair Value Assets, Gains (Losses) Included In Earnings	[8]	15				15
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[8]	0				0
Fair Value Assets, Purchases	[8]	0				0
Fair Value Assets, Issuances	[8]	0				0
Fair Value Assets, Settlements	[8]	0				0
Fair Value Assets, Transfers Into Level 3	[8]	0				0
Fair Value Assets, Transfers Out of Level 3	[8]	0				0
Fair Value Assets, Ending Balance	[8]	15				15
Fair Value Assets, Current Period Unrealized Gains (Losses)	[8]	$ 15				$ 15

[1] Level 3 net derivatives included derivative assets of $294 million and derivative liabilities of $169 million at September 30, 2017 and derivative assets of $335 million and derivative liabilities of $122 million at September 30, 2016. Gains (losses) on derivatives, net are predominantly included in trading revenue in the consolidated statement of income.

[2] Consists of swap agreements entered into in conjunction with the sales of certain Visa Class B Shares.

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

[4] Represents counterparty and cash collateral netting which allow the offsetting of amounts relating to certain contracts if certain conditions are met.

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

[6] During the fourth quarter of 2016, we sold our remaining residential mortgage servicing rights portfolio to a third party. Gains (losses) on residential mortgage servicing rights were included in residential mortgage banking revenue (expense) in the consolidated statement of income.

[7] See Note 10, "Fair Value Option," for additional information. Beginning January 1, 2017, unrealized gains (losses) on fair value option liabilities attributable to our own credit spread is recorded in other comprehensive income (loss).

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