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, 2015		Sep. 30, 2014		Jun. 30, 2014		Sep. 30, 2015		Sep. 30, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		$ 3,423		$ 3,581				$ 3,504		$ 3,150
Fair Value Assets, Purchases		7		10				22		574
Fair Value Assets, Issuances		0		0				0		0
Fair Value Assets, Settlements		(34)		(45)				(125)		(118)
Fair Value Assets, Transfers Into Level 3		0		(1)				0		7
Fair Value Assets, Transfers Out of Level 3		2		(1)				2		(101)
Fair Value Assets, Ending Balance		3,301		3,515		$ 3,581		3,301		3,515
Fair Value Assets, Current Period Unrealized Gains (Losses)		(108)		(47)				(167)		(119)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(2,479)		(2,995)				(2,615)		(3,234)
Fair Value Liability, Purchases		0		0				0		0
Fair Value Liability, Issuances		(272)		(193)				(693)		(505)
Fair Value Liability, Settlements		143		211				510		630
Fair Value Liability, Transfers Into Level 3		(45)		(61)				(67)		(110)
Fair Value Liability, Transfers Out of Level 3		72		476				283		772
Fair Value Liability, Ending Balance		(2,499)		(2,537)		(2,995)		(2,499)		(2,537)
Fair Value Liability, Current Period Unrealized Gains (Losses)		86		35				102		(25)
Interest rate contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	1		0				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]	0		4		0		0		4
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	(1)		3				0		3
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		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		0				0		(12)
Fair Value Assets, Transfers Into Level 3	[1]	0		0				0		0
Fair Value Assets, Transfers Out of Level 3	[1]	0		0				0		(93)
Fair Value Assets, Ending Balance	[1]	0		(3)		0		0		(3)
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	0		(3)				0		(1)
Equity contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	(10)		59				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]	(17)		(23)				(65)		(59)
Fair Value Assets, Transfers Into Level 3	[1]	0		(1)				0		7
Fair Value Assets, Transfers Out of Level 3	[1]	2		(1)				2		(3)
Fair Value Assets, Ending Balance	[1]	(95)		13		59		(95)		13
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	(79)		(32)				(101)		8
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				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]	179		257				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]	0		(5)				(9)		2
Fair Value Assets, Transfers Into Level 3	[1]	0		0				0		0
Fair Value Assets, Transfers Out of Level 3	[1]	0		0				0		114
Fair Value Assets, Ending Balance	[1]	171		221		257		171		221
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	(7)		(36)				(60)		(134)
Collateralized debt obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		240		260				253		254
Fair Value Assets, Purchases		0		0				0		0
Fair Value Assets, Issuances		0		0				0		0
Fair Value Assets, Settlements		(10)		(11)				(35)		(19)
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		233		269		260		233		269
Fair Value Assets, Current Period Unrealized Gains (Losses)		0		19				7		31
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		2,855		2,819				2,840		2,260
Fair Value Assets, Purchases		7		10				22		574
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		2,862		2,829		2,819		2,862		2,829
Fair Value Assets, Current Period Unrealized Gains (Losses)		0		0				0		(4)
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						121
Fair Value Assets, Purchases				0						0
Fair Value Assets, Issuances				0						0
Fair Value Assets, Settlements				0						(7)
Fair Value Assets, Transfers Into Level 3				0						0
Fair Value Assets, Transfers Out of Level 3				0		(119)				(119)
Fair Value Assets, Ending Balance				0		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]	158		186				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]	(7)		(6)				(16)		(23)
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]	130		182		186		130		182
Fair Value Assets, Current Period Unrealized Gains (Losses)	[2]	(21)		2				(13)		(22)
Domestic Deposits [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(1,817)		(2,257)	[3]			(1,968)		(2,334)	[3]
Fair Value Liability, Purchases		0		0	[3]			0		0	[3]
Fair Value Liability, Issuances		(86)		(111)	[3]			(270)		(271)	[3]
Fair Value Liability, Settlements		130		129	[3]			313		428	[3]
Fair Value Liability, Transfers Into Level 3	[3]	(44)		(59)				(66)		(108)
Fair Value Liability, Transfers Out of Level 3		54		395	[3]			233		591	[3]
Fair Value Liability, Ending Balance		(1,754)		(1,905)	[3]	(2,257)	[3]	(1,754)		(1,905)	[3]
Fair Value Liability, Current Period Unrealized Gains (Losses)		15		26	[3]			21		(10)	[3]
Long-term debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(662)		(738)	[3]			(647)		(900)	[3]
Fair Value Liability, Purchases		0		0	[3]			0		0	[3]
Fair Value Liability, Issuances		(186)		(82)	[3]			(423)		(234)	[3]
Fair Value Liability, Settlements		13		82	[3]			197		202	[3]
Fair Value Liability, Transfers Into Level 3		(1)		(2)	[3]			(1)		(2)	[3]
Fair Value Liability, Transfers Out of Level 3		18		81	[3]			50		181	[3]
Fair Value Liability, Ending Balance		(745)		(632)	[3]	$ (738)	[3]	(745)		(632)	[3]
Fair Value Liability, Current Period Unrealized Gains (Losses)		71		9	[3]			81		(15)	[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]	(75)		(31)				(89)		25
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		4				0		3
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		(3)				0		7
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]	(70)		(21)				(74)		65
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]	(8)		(31)				(30)		(86)
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		20				15		34
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]			0						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] | 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]	(22)		2				(13)		(22)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Gains (Losses) Included In Revenue	[4]	82		25				83		(90)
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)		0				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] | 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]	(21)		2				(13)		(22)
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]	9	[5]	(2)	[3]			4	[5]	(211)	[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]	$ 73	[5]	$ 27	[3]			$ 79	[5]	$ 121	[3]

[1] Level 3 net derivatives included derivative assets of $304 million and derivative liabilities of $228 million as of September 30, 2015 and derivative assets of $466 million and derivative liabilities of $231 million as of September 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.