Fair Value Measurements - Changes in Fair Value of Level 3 Assets and Liabilities (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended					9 Months Ended
	Sep. 30, 2014		Jun. 30, 2014	Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	$ 3,581			$ 2,615		$ 3,150		$ 3,690
Fair Value Assets, Purchases	10			15		574		282
Fair Value Assets, Issuances	0			0		0		11
Fair Value Assets, Settlements	(45)			(106)		(118)		(1,393)
Fair Value Assets, Transfers Into Level 3	(1)			5		7		(42)
Fair Value Assets, Transfers Out of Level 3	(1)			(4)		(101)		(25)
Fair Value Assets, Ending Balance	3,515			2,575		3,515		2,575
Fair Value Assets, Current Period Unrealized Gains (Losses)	(47)			47		(119)		(17)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance	(2,995)			(3,120)		(3,234)		(3,064)
Fair Value Liability, Purchases	0			0		0		0
Fair Value Liability, Issuances	(193)			(229)		(505)		(983)
Fair Value Liability, Settlements	211			168		630		492
Fair Value Liability, Transfers Into Level 3	(61)			(109)		(110)		(266)
Fair Value Liability, Transfers Out of Level 3	476			103		772		527
Fair Value Liability, Ending Balance	(2,537)			(3,229)		(2,537)		(3,229)
Fair Value Liability, Current Period Unrealized Gains (Losses)	35			(36)		(25)		(95)
Interest rate contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	0	[1]		(1)	[1]	1	[1]	7	[1]
Fair Value Assets, Purchases	0	[1]		0	[1]	0	[1]	0	[1]
Fair Value Assets, Issuances	0	[1]		0	[1]	0	[1]	0	[1]
Fair Value Assets, Settlements	0	[1]		0	[1]	0	[1]	0	[1]
Fair Value Assets, Transfers Into Level 3	0	[1]		0	[1]	0	[1]	0	[1]
Fair Value Assets, Transfers Out of Level 3	0	[1]		0	[1]	0	[1]	0	[1]
Fair Value Assets, Ending Balance	4	[1]		1	[1]	4	[1]	1	[1]
Fair Value Assets, Current Period Unrealized Gains (Losses)	3	[1]		2	[1]	3	[1]	(7)	[1]
Foreign exchange contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		[1]		104	[1]	95	[1]	5	[1]
Fair Value Assets, Purchases	0	[1]		0	[1]	0	[1]	0	[1]
Fair Value Assets, Issuances	0	[1]		0	[1]	0	[1]	0	[1]
Fair Value Assets, Settlements	0	[1]		(6)	[1]	(12)	[1]	110	[1]
Fair Value Assets, Transfers Into Level 3	0	[1]		1	[1]	0	[1]	(12)	[1]
Fair Value Assets, Transfers Out of Level 3	0	[1]		0	[1]	(93)	[1]	0	[1]
Fair Value Assets, Ending Balance	(3)	[1]		105	[1]	(3)	[1]	105	[1]
Fair Value Assets, Current Period Unrealized Gains (Losses)	(3)	[1]		0	[1]	(1)	[1]	107	[1]
Equity contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	59	[1]		(83)	[1]	3	[1]	(7)	[1]
Fair Value Assets, Purchases	0	[1]		0	[1]	0	[1]	0	[1]
Fair Value Assets, Issuances	0	[1]		0	[1]	0	[1]	0	[1]
Fair Value Assets, Settlements	(23)	[1]		(5)	[1]	(59)	[1]	(52)	[1]
Fair Value Assets, Transfers Into Level 3	(1)	[1]		4	[1]	7	[1]	16	[1]
Fair Value Assets, Transfers Out of Level 3	(1)	[1]		(4)	[1]	(3)	[1]	(25)	[1]
Fair Value Assets, Ending Balance	13	[1]		(38)	[1]	13	[1]	(38)	[1]
Fair Value Assets, Current Period Unrealized Gains (Losses)	(32)	[1]		47	[1]	8	[1]	(28)	[1]
Precious metals contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	0	[1]		0		(2)	[1]	0	[1]
Fair Value Assets, Purchases	0	[1]		0		0	[1]	0	[1]
Fair Value Assets, Issuances	0	[1]		0		0	[1]	0	[1]
Fair Value Assets, Settlements	0	[1]		0		0	[1]	0	[1]
Fair Value Assets, Transfers Into Level 3	0	[1]		0		0	[1]	0	[1]
Fair Value Assets, Transfers Out of Level 3	0	[1]		0		0	[1]	0	[1]
Fair Value Assets, Ending Balance	0	[1]		(1)	[1]	0	[1]	(1)	[1]
Fair Value Assets, Current Period Unrealized Gains (Losses)	0	[1]		(1)		0	[1]	(1)	[1]
Credit contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	257	[1]		225	[1]	191	[1]	571	[1]
Fair Value Assets, Purchases	0	[1]		0	[1]	0	[1]	0	[1]
Fair Value Assets, Issuances	0	[1]		0	[1]	0	[1]	0	[1]
Fair Value Assets, Settlements	(5)	[1]		14	[1]	2	[1]	(126)	[1]
Fair Value Assets, Transfers Into Level 3	0	[1]		0	[1]	0	[1]	(46)	[1]
Fair Value Assets, Transfers Out of Level 3	0	[1]		0	[1]	114	[1]	0	[1]
Fair Value Assets, Ending Balance	221			213	[1]	221		213	[1]
Fair Value Assets, Current Period Unrealized Gains (Losses)	(36)	[1]		(18)	[1]	(134)	[1]	(287)	[1]
Collateralized debt obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	260			227		254		466
Fair Value Assets, Purchases	0			0		0		236
Fair Value Assets, Issuances	0			0		0		0
Fair Value Assets, Settlements	(11)			(3)		(19)		(596)
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	269			245		269		245
Fair Value Assets, Current Period Unrealized Gains (Losses)	19			20		31		137
Corporate and other domestic [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	2,819			1,498		2,260		1,861
Fair Value Assets, Purchases	10			15		574		46
Fair Value Assets, Issuances	0			0		0		0
Fair Value Assets, Settlements	0			0		0		(422)
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	2,829			1,513		2,829		1,513
Fair Value Assets, Current Period Unrealized Gains (Losses)	0			0		(4)		28
Corporate debt securities issued by foreign entities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance				285				299
Fair Value Assets, Purchases				0				0
Fair Value Assets, Issuances				0				0
Fair Value Assets, Settlements				(99)				(99)
Fair Value Assets, Transfers Into Level 3				0				0
Fair Value Assets, Transfers Out of Level 3				0				0
Fair Value Assets, Ending Balance				192				192
Fair Value Assets, Current Period Unrealized Gains (Losses)				6				(8)
Government debt securities issued by foreign entities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	0			135		121		311
Fair Value Assets, Purchases	0			0		0		0
Fair Value Assets, Issuances	0			0		0		0
Fair Value Assets, Settlements	0			(7)		(7)		(204)
Fair Value Assets, Transfers Into Level 3	0			0		0		0
Fair Value Assets, Transfers Out of Level 3	0		(119)	0		(119)		0
Fair Value Assets, Ending Balance	0		0	121		0		121
Fair Value Assets, Current Period Unrealized Gains (Losses)	0			(8)		0		2
Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance				0				9
Fair Value Assets, Purchases				0				0
Fair Value Assets, Issuances				0				0
Fair Value Assets, Settlements				0				(4)
Fair Value Assets, Transfers Into Level 3				0				0
Fair Value Assets, Transfers Out of Level 3				0				0
Fair Value Assets, Ending Balance				0				0
Fair Value Assets, Current Period Unrealized Gains (Losses)				0				(5)
Mortgage servicing rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	186	[1],[2]		225	[1],[3]	227	[1],[2]	168	[1],[2]
Fair Value Assets, Purchases	0	[1],[2]		0	[1],[3]	0	[1],[2]	0	[1],[2]
Fair Value Assets, Issuances	0	[1],[2]		0	[1],[3]	0	[1],[2]	11	[1],[2]
Fair Value Assets, Settlements	(6)	[1],[2]		0	[1],[3]	(23)	[1],[2]	0	[1],[2]
Fair Value Assets, Transfers Into Level 3	0	[1],[2]		0	[1],[3]	0	[1],[2]	0	[1],[2]
Fair Value Assets, Transfers Out of Level 3	0	[1],[2]		0	[1],[3]	0	[1],[2]	0	[1],[2]
Fair Value Assets, Ending Balance	182	[1],[2]		224	[1],[2],[3]	182	[1],[2]	224	[1],[2],[3]
Fair Value Assets, Current Period Unrealized Gains (Losses)	2	[1],[2]		(1)	[1],[3]	(22)	[1],[2]	45	[1],[2]
Deposits [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance	(2,257)			(2,448)		(2,334)		(2,635)
Fair Value Liability, Purchases	0			0		0		0
Fair Value Liability, Issuances	(111)			(73)		(271)		(558)
Fair Value Liability, Settlements	129			85		428		304
Fair Value Liability, Transfers Into Level 3	(59)			(84)		(108)		(241)
Fair Value Liability, Transfers Out of Level 3	395			79		591		323
Fair Value Liability, Ending Balance	(1,905)			(2,474)		(1,905)		(2,474)
Fair Value Liability, Current Period Unrealized Gains (Losses)	26			(18)		(10)		133
Long-term debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance	(738)			(672)		(900)		(429)
Fair Value Liability, Purchases	0			0		0		0
Fair Value Liability, Issuances	(82)			(156)		(234)		(425)
Fair Value Liability, Settlements	82			83		202		188
Fair Value Liability, Transfers Into Level 3	(2)			(25)		(2)		(25)
Fair Value Liability, Transfers Out of Level 3	81			24		181		204
Fair Value Liability, Ending Balance	(632)			(755)		(632)		(755)
Fair Value Liability, Current Period Unrealized Gains (Losses)	9			(18)		(15)		(228)
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	(31)	[4]		49	[4]	25	[4]	13	[4]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Gains (Losses) Included In Revenue	25	[4]		(42)	[4]	(90)	[4]	65	[4]
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	4	[1],[4]		0	[1],[4]	3	[1],[4]	0	[1],[4]
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	(3)	[1],[4]		6	[1],[4]	7	[1],[4]	2	[1],[4]
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	(21)	[1],[4]		50	[1],[4]	65	[1],[4]	30	[1],[4]
Trading Gain (Loss) [Member] | Precious metals contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	0	[1],[4]		(1)		2	[1],[4]	(1)	[1],[4]
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	(31)	[1],[4]		(26)	[1],[4]	(86)	[1],[4]	(186)	[1],[4]
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	20	[4]		21	[4]	34	[4]	139	[4]
Trading Gain (Loss) [Member] | Corporate and other domestic [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	0	[4]		0	[4]	(5)	[4]	28	[4]
Trading Gain (Loss) [Member] | Corporate debt securities issued by foreign entities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue				6	[4]			(8)	[4]
Trading Gain (Loss) [Member] | Government debt securities issued by foreign entities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	0	[4]		(7)	[4]	5	[4]	14	[4]
Trading Gain (Loss) [Member] | Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue				0	[4]			(5)	[4]
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	0	[1],[2],[4]		0	[1],[4]	0	[1],[2],[4]	0	[1],[2],[4]
Trading Gain (Loss) [Member] | Deposits [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Gains (Losses) Included In Revenue	(2)	[4]		(33)	[4]	(211)	[4]	333	[4]
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	27	[4]		(9)	[4]	121	[4]	(268)	[4]
Other Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	2	[4]		1	[4]	(22)	[4]	39	[4]
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	0	[1],[4]		2	[1],[4]	0	[1],[4]	(6)	[1],[4]
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	0	[1],[4]		0	[1],[4]	0	[1],[4]	0	[1],[4]
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	0	[1],[4]		0	[1],[4]	0	[1],[4]	0	[1],[4]
Other Income [Member] | Precious metals contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	0	[1],[4]		0		0	[1],[4]	0	[1],[4]
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	0	[1],[4]		0	[1],[4]	0	[1],[4]	0	[1],[4]
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	0	[4]		0	[4]	0	[4]	0	[4]
Other Income [Member] | Corporate and other domestic [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	0	[4]		0	[4]	0	[4]	0	[4]
Other Income [Member] | Corporate debt securities issued by foreign entities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue				0	[4]			0	[4]
Other Income [Member] | Government debt securities issued by foreign entities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue	0	[4]		0	[4]	0	[4]	0	[4]
Other Income [Member] | Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Gains (Losses) Included In Revenue				0	[4]			0	[4]
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	[1],[2],[4]		$ (1)	[1],[4]	$ (22)	[1],[2],[4]	$ 45	[1],[2],[4]

[1] Level 3 net derivatives included derivative assets of $466 million and derivative liabilities of $231 million as of September 30, 2014 and derivative assets of $897 million and derivative liabilities of $618 million as of September 30, 2013.

[2] See Note 7, "Intangible Assets," for additional information.

[3] Includes certain commercial loans held for sale which we have elected to apply the fair value option. See Note 6, "Loans Held for Sale," for further information.

[4] Includes realized and unrealized gains and losses.