Fair Value Measurements - Changes in Fair Value of Level 3 Assets and Liabilities (Detail) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2016		Sep. 30, 2015		Sep. 30, 2016		Sep. 30, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		$ 3,358		$ 3,423		$ 3,328		$ 3,504
Fair Value Assets, Purchases		4		7		14		22
Fair Value Assets, Issuances		0		0		0		0
Fair Value Assets, Settlements		(13)		(34)		(32)		(125)
Fair Value Assets, Transfers Into Level 3		(1)		0		0		0
Fair Value Assets, Transfers Out of Level 3		(92)		2		(92)		2
Fair Value Assets, Ending Balance		3,288		3,301		3,288		3,301
Fair Value Assets, Current Period Unrealized Gains (Losses)		(4)		(108)		31		(167)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(2,250)		(2,479)		(2,613)		(2,615)
Fair Value Liability, Purchases		0		0		0		0
Fair Value Liability, Issuances		(128)		(272)		(422)		(693)
Fair Value Liability, Settlements		410		143		858		510
Fair Value Liability, Transfers Into Level 3		(39)		(45)		(54)		(67)
Fair Value Liability, Transfers Out of Level 3		124		72		411		283
Fair Value Liability, Ending Balance		(1,917)		(2,499)		(1,917)		(2,499)
Fair Value Liability, Current Period Unrealized Gains (Losses)		(68)		86		(69)		102
Interest rate contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	1		1		1		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]	1		0		1		0
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	0		(1)		0		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, 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]	(15)		(10)		(83)		42
Fair Value Assets, Purchases	[1]	0		0		0		0
Fair Value Assets, Issuances	[1]	0		0		0		0
Fair Value Assets, Settlements	[1]	(2)		(17)		10		(65)
Fair Value Assets, Transfers Into Level 3	[1]	(1)		0		0		0
Fair Value Assets, Transfers Out of Level 3	[1]	3		2		3		2
Fair Value Assets, Ending Balance	[1]	5		(95)		5		(95)
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	0		(79)		50		(101)
Credit contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	188		179		179		210
Fair Value Assets, Purchases	[1]	0		0		0		0
Fair Value Assets, Issuances	[1]	0		0		0		0
Fair Value Assets, Settlements	[1]	8		0		1		(9)
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]	207		171		207		171
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	(3)		(7)		18		(60)
Collateralized debt obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		201		240		221		253
Fair Value Assets, Purchases		0		0		0		0
Fair Value Assets, Issuances		0		0		0		0
Fair Value Assets, Settlements		(14)		(10)		(26)		(35)
Fair Value Assets, Transfers Into Level 3		0		0		0		0
Fair Value Assets, Transfers Out of Level 3		0		0		0		0
Fair Value Assets, Ending Balance		191		233		191		233
Fair Value Assets, Current Period Unrealized Gains (Losses)		2		0		(9)		7
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		2,879		2,855		2,870		2,840
Fair Value Assets, Purchases		4		7		14		22
Fair Value Assets, Issuances		0		0		0		0
Fair Value Assets, Settlements		0		0		0		0
Fair Value Assets, Transfers Into Level 3		0		0		0		0
Fair Value Assets, Transfers Out of Level 3		0		0		0		0
Fair Value Assets, Ending Balance		2,884		2,862		2,884		2,862
Fair Value Assets, Current Period Unrealized Gains (Losses)		1		0		0		0
Mortgage servicing rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[2]	104		158		140		159
Fair Value Assets, Purchases	[2]	0		0		0		0
Fair Value Assets, Issuances	[2]	0		0		0		0
Fair Value Assets, Settlements	[2]	(5)		(7)		(17)		(16)
Fair Value Assets, Transfers Into Level 3	[2]	0		0		0		0
Fair Value Assets, Transfers Out of Level 3	[2]	(95)		0		(95)		0
Fair Value Assets, Ending Balance	[2]	0		130		0		130
Fair Value Assets, Current Period Unrealized Gains (Losses)	[2]	(4)		(21)		(28)		(13)
Domestic Deposits [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(1,677)		(1,817)	[3]	(1,867)		(1,968)	[3]
Fair Value Liability, Purchases		0		0	[3]	0		0	[3]
Fair Value Liability, Issuances		(42)		(86)	[3]	(206)		(270)	[3]
Fair Value Liability, Settlements		300		130	[3]	599		313	[3]
Fair Value Liability, Transfers Into Level 3	[3]	(39)		(44)		(54)		(66)
Fair Value Liability, Transfers Out of Level 3		57		54	[3]	198		233	[3]
Fair Value Liability, Ending Balance		(1,404)		(1,754)	[3]	(1,404)		(1,754)	[3]
Fair Value Liability, Current Period Unrealized Gains (Losses)		(26)		15	[3]	(46)		21	[3]
Long-term debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(573)		(662)	[3]	(746)		(647)	[3]
Fair Value Liability, Purchases		0		0	[3]	0		0	[3]
Fair Value Liability, Issuances		(86)		(186)	[3]	(216)		(423)	[3]
Fair Value Liability, Settlements		110		13	[3]	259		197	[3]
Fair Value Liability, Transfers Into Level 3		0		(1)	[3]	0		(1)	[3]
Fair Value Liability, Transfers Out of Level 3		67		18	[3]	213		50	[3]
Fair Value Liability, Ending Balance		(513)		(745)	[3]	(513)		(745)	[3]
Fair Value Liability, Current Period Unrealized Gains (Losses)		(42)		71	[3]	(23)		81	[3]
Trading Gain (Loss) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[4]	36		(75)		98		(89)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Gains (Losses) Included In Revenue	[4]	0		0		0		0
Trading Gain (Loss) [Member] | Interest rate contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[1],[4]	0		0		0		0
Trading Gain (Loss) [Member] | Foreign exchange contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[1],[4]	0		0		0		0
Trading Gain (Loss) [Member] | Equity contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[1],[4]	20		(70)		75		(74)
Trading Gain (Loss) [Member] | Credit contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[1],[4]	11		(8)		27		(30)
Trading Gain (Loss) [Member] | Collateralized debt obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[4]	4		3		(4)		15
Trading Gain (Loss) [Member] | Corporate and other domestic debt securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[4]	1		0		0		0
Trading Gain (Loss) [Member] | Mortgage servicing rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[2],[4]	0		0		0		0
Trading Gain (Loss) [Member] | Domestic Deposits [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Gains (Losses) Included In Revenue	[4]	0	[5]	0	[3]	0	[5]	0	[3]
Trading Gain (Loss) [Member] | Long-term debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Gains (Losses) Included In Revenue	[4]	0	[5]	0	[3]	0	[5]	0	[3]
Other Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[4]	(4)		(22)		(28)		(13)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Gains (Losses) Included In Revenue	[4]	(34)		82		(97)		83
Other Income [Member] | Interest rate contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[1],[4]	0		(1)		0		0
Other Income [Member] | Foreign exchange contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[1],[4]	0		0		0		0
Other Income [Member] | Equity contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[1],[4]	0		0		0		0
Other Income [Member] | Credit contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[1],[4]	0		0		0		0
Other Income [Member] | Collateralized debt obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[4]	0		0		0		0
Other Income [Member] | Corporate and other domestic debt securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[4]	0		0		0		0
Other Income [Member] | Mortgage servicing rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	[2],[4]	(4)		(21)		(28)		(13)
Other Income [Member] | Domestic Deposits [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Gains (Losses) Included In Revenue	[4]	(3)	[5]	9	[3]	(74)	[5]	4	[3]
Other Income [Member] | Long-term debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Gains (Losses) Included In Revenue	[4]	$ (31)	[5]	$ 73	[3]	$ (23)	[5]	$ 79	[3]

[1] Level 3 net derivatives included derivative assets of $335 million and derivative liabilities of $122 million at September 30, 2016 and derivative assets of $304 million and derivative liabilities of $228 million at September 30, 2015.

[2] See Note 7, "Intangible Assets," and Note 9, "Other Assets Held for Sale," for additional information.

[3] See Note 11, "Fair Value Option," for additional information.

[4] Includes realized and unrealized gains and losses.

[5] See Note 7, "Intangible Assets," and Note 9, "Other Assets Held for Sale," for additional information.