Fair Value Measurement- Significant Unobservable Inputs (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Fair value measurements for assets using significant unobservable inputs
Beginning balance			$ 209				$ 271
Transfers out of Level 3			(14)				(19)
Included in earnings (or changes in net assets)			(4)				(5)
Purchases							3
Sales			(10)				(69)
Ending balance			181				181
Change in unrealized gains or (losses) for the period included in earnings (or changes in net assets) for assets held at the end of the reporting period			(2)				(13)
Fair value measurements for liabilities using significant unobservable inputs
Beginning balance	51		117		75		224
Transfers out of Level 3	(2)		(13)		(39)		(17)
Included in earnings (or changes in net liabilities)	(23)		(5)		(13)		(110)
Purchases					3
Settlements			(7)				(5)
Ending balance	26		92		26		92
Change in unrealized (gains) or losses for the period included in earnings (or changes in net assets) for liabilities held at the end of the reporting period	(12)		(1)		1		27
Debt and equity instruments
Fair value measurements for assets using significant unobservable inputs
Change in unrealized gains or (losses) for the period included in earnings (or changes in net assets) for assets held at the end of the reporting period					0
Derivative assets
Fair value measurements for assets using significant unobservable inputs
Change in unrealized gains or (losses) for the period included in earnings (or changes in net assets) for assets held at the end of the reporting period					19	[1]
Other Assets
Fair value measurements for assets using significant unobservable inputs
Beginning balance	98		113		105		120
Transfers out of Level 3	0		0		0		0
Included in earnings (or changes in net assets)	(10)	[2]	(2)	[2]	(5)	[2]	(2)	[2]
Purchases					14		3
Sales	(9)		(10)		(35)		(20)
Settlements	0				0
Ending balance	79		101		79		101
Change in unrealized gains or (losses) for the period included in earnings (or changes in net assets) for assets held at the end of the reporting period	0		0		0		0
Total Assets
Fair value measurements for assets using significant unobservable inputs
Beginning balance	132				139
Transfers out of Level 3	(10)				(12)
Included in earnings (or changes in net assets)	3				10
Purchases					14
Sales	(9)				(35)
Settlements	(2)				(2)
Ending balance	114				114
Change in unrealized gains or (losses) for the period included in earnings (or changes in net assets) for assets held at the end of the reporting period	16				19
Securities available-for-sale | State and political subdivisions
Fair value measurements for assets using significant unobservable inputs
Beginning balance	11		52		11		45
Transfers out of Level 3	0		0		0		0
Included in earnings (or changes in net assets)	0	[3]	(1)	[3]	0	[3]	6	[3]
Purchases					0
Sales	0		0		0
Settlements	0				0
Ending balance	11		51		11		51
Trading Assets | Debt and equity instruments
Fair value measurements for assets using significant unobservable inputs
Beginning balance	1		2		1		48
Transfers out of Level 3	0		0		0		0
Included in earnings (or changes in net assets)	0	[4]	1	[4]	0	[4]	4	[4]
Purchases					0		0
Sales	0		0		0		(49)
Settlements	(1)				(1)
Ending balance	0		3		0		3
Change in unrealized gains or (losses) for the period included in earnings (or changes in net assets) for assets held at the end of the reporting period	0		0				0
Trading Assets | Derivative assets
Fair value measurements for assets using significant unobservable inputs
Beginning balance	22	[1]	42	[1]	22	[1]	58	[1]
Transfers out of Level 3	(10)	[1]	(14)	[1]	(12)	[1]	(19)	[1]
Included in earnings (or changes in net assets)	13	[1],[4]	(2)	[1],[4]	15	[1],[4]	(13)	[1],[4]
Purchases					0	[1]	0	[1]
Sales	0	[1]	0	[1]	0	[1]	0	[1]
Settlements	(1)	[1]			(1)	[1]
Ending balance	24	[1]	26	[1]	24	[1]	26	[1]
Change in unrealized gains or (losses) for the period included in earnings (or changes in net assets) for assets held at the end of the reporting period	16	[1]	(2)	[1]			(13)	[1]
Trading Liabilities | Derivative liabilities
Fair value measurements for liabilities using significant unobservable inputs
Beginning balance	51	[5]	117	[5]	75	[5]	224	[5]
Transfers out of Level 3	(2)		(13)	[5]	(39)	[5]	(17)	[5]
Included in earnings (or changes in net liabilities)	(23)	[4],[5]	(5)	[4],[5]	(13)	[4],[5]	(110)	[4],[5]
Purchases					3	[5]
Settlements			(7)				(5)	[5]
Ending balance	26	[5]	92	[5]	26	[5]	92	[5]
Change in unrealized (gains) or losses for the period included in earnings (or changes in net assets) for liabilities held at the end of the reporting period	(12)	[5]	(1)	[5]	1	[5]	27	[5]
Investment Management funds
Fair value measurements for assets using significant unobservable inputs
Beginning balance			44				44
Transfers out of Level 3			0				0
Included in earnings (or changes in net assets)			2	[6]			2	[6]
Purchases							0
Sales			(46)				(46)
Ending balance			0				0
Change in unrealized gains or (losses) for the period included in earnings (or changes in net assets) for assets held at the end of the reporting period			$ 0				$ 0

[1] Derivative assets are reported on a gross basis.

[2] Reported in investment and other income.

[3] Realized gains (losses) are reported in securities gains (losses). Unrealized gains (losses) are reported in accumulated other comprehensive income (loss) except for the credit portion of OTTI losses which are recorded in securities gains (losses).

[4] Reported in foreign exchange and other trading revenue.

[5] Derivative liabilities are reported on a gross basis.

[6] Reported in income from consolidated investment management funds.