Fair Value Measurements - Changes in Fair Value of Level 3 Assets and Liabilities (Detail) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		$ 3,497		$ 3,690		$ 3,504		$ 3,150
Fair Value Assets, Purchases		7		11		15		564
Fair Value Assets, Issuances		0		0		0		0
Fair Value Assets, Settlements		(48)		(45)		(91)		(73)
Fair Value Assets, Transfers Into Level 3		0		2		0		6
Fair Value Assets, Transfers Out of Level 3		1		(107)		0		(98)
Fair Value Assets, Ending Balance		3,423		3,581		3,423		3,581
Fair Value Assets, Current Period Unrealized Gains (Losses)		(25)		(2)		(60)		(61)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(2,568)		(2,976)		(2,615)		(3,234)
Fair Value Liability, Purchases		0		0		0		0
Fair Value Liability, Issuances		(245)		(245)		(421)		(313)
Fair Value Liability, Settlements		239		203		367		418
Fair Value Liability, Transfers Into Level 3		(22)		(27)		(22)		(95)
Fair Value Liability, Transfers Out of Level 3		90		131		211		342
Fair Value Liability, Ending Balance		(2,479)		(2,995)		(2,479)		(2,995)
Fair Value Liability, Current Period Unrealized Gains (Losses)		33		(56)		16		(74)
Interest rate contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	20		1		0		1
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]	1		0		1		(1)
Foreign exchange contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	0		96		0		95
Fair Value Assets, Purchases	[1]	0		0		0		0
Fair Value Assets, Issuances	[1]	0		0		0		0
Fair Value Assets, Settlements	[1]	0		(6)		0		(12)
Fair Value Assets, Transfers Into Level 3	[1]	0		0		0		0
Fair Value Assets, Transfers Out of Level 3	[1]	0		(98)		0		(93)
Fair Value Assets, Ending Balance	[1]	0		0		0		0
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	0		4		0		5
Equity contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	43		24		42		3
Fair Value Assets, Purchases	[1]	0		0		0		0
Fair Value Assets, Issuances	[1]	0		0		0		0
Fair Value Assets, Settlements	[1]	(27)		(29)		(48)		(36)
Fair Value Assets, Transfers Into Level 3	[1]	0		2		0		6
Fair Value Assets, Transfers Out of Level 3	[1]	1		(4)		0		0
Fair Value Assets, Ending Balance	[1]	(10)		59		(10)		59
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	(34)		41		(22)		49
Precious metals contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]			0				(2)
Fair Value Assets, Purchases	[1]			0				0
Fair Value Assets, Issuances	[1]			0				0
Fair Value Assets, Settlements	[1]			0				0
Fair Value Assets, Transfers Into Level 3	[1]			0				0
Fair Value Assets, Transfers Out of Level 3	[1]			0				0
Fair Value Assets, Ending Balance	[1]			0				0
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]			0				0
Credit contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	192		181		210		191
Fair Value Assets, Purchases	[1]	0		0		0		0
Fair Value Assets, Issuances	[1]	0		0		0		0
Fair Value Assets, Settlements	[1]	(3)		3		(9)		7
Fair Value Assets, Transfers Into Level 3	[1]	0		0		0		0
Fair Value Assets, Transfers Out of Level 3	[1]	0		114		0		114
Fair Value Assets, Ending Balance	[1]	179		257		179		257
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	(13)		(42)		(53)		(98)
Collateralized debt obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		254		258		253		254
Fair Value Assets, Purchases		0		0		0		0
Fair Value Assets, Issuances		0		0		0		0
Fair Value Assets, Settlements		(17)		(5)		(25)		(8)
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		240		260		240		260
Fair Value Assets, Current Period Unrealized Gains (Losses)		0		7		7		14
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		2,848		2,808		2,840		2,260
Fair Value Assets, Purchases		7		11		15		564
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		2,855		2,819		2,855		2,819
Fair Value Assets, Current Period Unrealized Gains (Losses)		0		0		0		(6)
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				117				121
Fair Value Assets, Purchases				0				0
Fair Value Assets, Issuances				0				0
Fair Value Assets, Settlements				(1)				(7)
Fair Value Assets, Transfers Into Level 3				0				0
Fair Value Assets, Transfers Out of Level 3				(119)				(119)
Fair Value Assets, Ending Balance				0				0
Fair Value Assets, Current Period Unrealized Gains (Losses)				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]	140		205		159		227
Fair Value Assets, Purchases	[2]	0		0		0		0
Fair Value Assets, Issuances	[2]	0		0		0		0
Fair Value Assets, Settlements	[2]	(1)		(7)		(9)		(17)
Fair Value Assets, Transfers Into Level 3	[2]	0		0		0		0
Fair Value Assets, Transfers Out of Level 3	[2]	0		0		0		0
Fair Value Assets, Ending Balance	[2]	158		186		158		186
Fair Value Assets, Current Period Unrealized Gains (Losses)	[2]	21		(12)		7		(24)
Deposits in domestic offices [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(1,926)		(2,244)	[3]	(1,968)		(2,334)	[3]
Fair Value Liability, Purchases		0		0	[3]	0		0	[3]
Fair Value Liability, Issuances		(95)		(135)	[3]	(184)		(160)	[3]
Fair Value Liability, Settlements		134		130	[3]	183		298	[3]
Fair Value Liability, Transfers Into Level 3		(22)		(27)	[3]	(22)	[3]	(95)	[3]
Fair Value Liability, Transfers Out of Level 3		78		104	[3]	179		244	[3]
Fair Value Liability, Ending Balance		(1,817)		(2,257)	[3]	(1,817)		(2,257)	[3]
Fair Value Liability, Current Period Unrealized Gains (Losses)		19		(34)	[3]	6		(51)	[3]
Long-term debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(642)		(732)	[3]	(647)		(900)	[3]
Fair Value Liability, Purchases		0		0	[3]	0		0	[3]
Fair Value Liability, Issuances		(150)		(110)	[3]	(237)		(153)	[3]
Fair Value Liability, Settlements		105		73	[3]	184		120	[3]
Fair Value Liability, Transfers Into Level 3		0		0	[3]	0		0	[3]
Fair Value Liability, Transfers Out of Level 3		12		27	[3]	32		98	[3]
Fair Value Liability, Ending Balance		(662)		(738)	[3]	(662)		(738)	[3]
Fair Value Liability, Current Period Unrealized Gains (Losses)		14		(22)	[3]	10		(23)	[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]	(54)		43		(14)		57
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]	(20)		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		8		0		10
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]	(27)		66		(4)		86
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	[1],[4]			0				2
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]	(10)		(41)		(22)		(55)
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]	3		7		12		14
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]	0		0		0		(5)
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	[4]			3				5
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] | Deposits in domestic offices [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]	20		(13)		9		(25)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Gains (Losses) Included In Revenue	[4]	27		(81)		1		(113)
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]	1		(1)		1		(1)
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] | 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	[1],[4]			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] | 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	[4]			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]	19		(12)		8		(24)
Other Income [Member] | Deposits in domestic offices [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Gains (Losses) Included In Revenue	[4]	14	[5]	(85)	[3]	(5)	[5]	(210)	[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]	$ 13	[5]	$ 4	[3]	$ 6	[5]	$ 97	[3]

[1] Level 3 net derivatives included derivative assets of $387 million and derivative liabilities of $217 million as of June 30, 2015 and derivative assets of $538 million and derivative liabilities of $222 million as of June 30, 2014.

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

[3] See Note 10, "Fair Value Option," for additional information.

[4] Includes realized and unrealized gains and losses.

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