Fair Value Measurements - Changes in Fair Value of Level 3 Assets and Liabilities (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016		Mar. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		$ 3,328		$ 3,504
Fair Value Assets, Purchases		5		8
Fair Value Assets, Issuances		0		0
Fair Value Assets, Settlements		(13)		(39)
Fair Value Assets, Transfers Into Level 3		1		0
Fair Value Assets, Transfers Out of Level 3		(1)		(1)
Fair Value Assets, Ending Balance		3,323		3,498
Fair Value Assets, Current Period Unrealized Gains (Losses)		(13)		(13)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(2,613)		(2,615)
Fair Value Liability, Purchases		0		0
Fair Value Liability, Issuances		(139)		(176)
Fair Value Liability, Settlements		153		128
Fair Value Liability, Transfers Into Level 3		(8)		0
Fair Value Liability, Transfers Out of Level 3		139		121
Fair Value Liability, Ending Balance		(2,495)		(2,568)
Fair Value Liability, Current Period Unrealized Gains (Losses)		(27)		(19)
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
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]	1		20
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	0		20
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
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
Equity contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	(83)		42
Fair Value Assets, Purchases	[1]	0		0
Fair Value Assets, Issuances	[1]	0		0
Fair Value Assets, Settlements	[1]	4		(21)
Fair Value Assets, Transfers Into Level 3	[1]	1		0
Fair Value Assets, Transfers Out of Level 3	[1]	(1)		(1)
Fair Value Assets, Ending Balance	[1]	(55)		43
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	24		14
Credit contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	179		210
Fair Value Assets, Purchases	[1]	0		0
Fair Value Assets, Issuances	[1]	0		0
Fair Value Assets, Settlements	[1]	(4)		(6)
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]	177		192
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	(13)		(40)
Collateralized debt obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		221		253
Fair Value Assets, Purchases		0		0
Fair Value Assets, Issuances		0		0
Fair Value Assets, Settlements		(6)		(8)
Fair Value Assets, Transfers Into Level 3		0		0
Fair Value Assets, Transfers Out of Level 3		0		0
Fair Value Assets, Ending Balance		210		254
Fair Value Assets, Current Period Unrealized Gains (Losses)		(6)		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		2,870		2,840
Fair Value Assets, Purchases		5		8
Fair Value Assets, Issuances		0		0
Fair Value Assets, Settlements		0		0
Fair Value Assets, Transfers Into Level 3		0		0
Fair Value Assets, Transfers Out of Level 3		0		0
Fair Value Assets, Ending Balance		2,873		2,848
Fair Value Assets, Current Period Unrealized Gains (Losses)		(2)		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		159
Fair Value Assets, Purchases	[2]	0		0
Fair Value Assets, Issuances	[2]	0		0
Fair Value Assets, Settlements	[2]	(7)		(4)
Fair Value Assets, Transfers Into Level 3	[2]	0		0
Fair Value Assets, Transfers Out of Level 3	[2]	0		0
Fair Value Assets, Ending Balance	[2]	117		141
Fair Value Assets, Current Period Unrealized Gains (Losses)	[2]	(16)		(14)
Domestic Deposits [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(1,867)		(1,968)	[3]
Fair Value Liability, Purchases		0		0	[3]
Fair Value Liability, Issuances		(64)		(89)	[3]
Fair Value Liability, Settlements		88		49	[3]
Fair Value Liability, Transfers Into Level 3	[3]	(8)		0
Fair Value Liability, Transfers Out of Level 3		55		101	[3]
Fair Value Liability, Ending Balance		(1,849)		(1,926)	[3]
Fair Value Liability, Current Period Unrealized Gains (Losses)		(50)		(13)	[3]
Long-term debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(746)		(647)	[3]
Fair Value Liability, Purchases		0		0	[3]
Fair Value Liability, Issuances		(75)		(87)	[3]
Fair Value Liability, Settlements		65		79	[3]
Fair Value Liability, Transfers Into Level 3		0		0	[3]
Fair Value Liability, Transfers Out of Level 3		84		20	[3]
Fair Value Liability, Ending Balance		(646)		(642)	[3]
Fair Value Liability, Current Period Unrealized Gains (Losses)		23		(6)	[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]	19		39
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Gains (Losses) Included In Revenue	[4]	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		19
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
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]	24		23
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]	2		(12)
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]	(5)		9
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]	(2)		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
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]
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]
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]	(16)		(13)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Gains (Losses) Included In Revenue	[4]	(27)		(26)
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
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
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
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
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
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
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]	(16)		(14)
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]	(53)	[5]	(19)	[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]	$ 26	[5]	$ (7)	[3]

[1] Level 3 net derivatives included derivative assets of $391 million and derivative liabilities of $268 million as of March 31, 2016 and derivative assets of $463 million and derivative liabilities of $208 million as of March 31, 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.