Fair Value Measurement- Significant Unobservable Inputs (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2010 Derivative assets		Mar. 31, 2013 Available-for-sale State and political subdivisions		Mar. 31, 2012 Available-for-sale State and political subdivisions		Mar. 31, 2013 Available-for-sale Other debt securities	Mar. 31, 2012 Available-for-sale Other debt securities		Mar. 31, 2013 Trading Assets Debt and equity instruments		Mar. 31, 2012 Trading Assets Debt and equity instruments		Mar. 31, 2013 Trading Assets Derivative assets		Mar. 31, 2012 Trading Assets Derivative assets		Mar. 31, 2013 Other Assets		Mar. 31, 2012 Other Assets	Mar. 31, 2012 Other Assets Derivative assets		Mar. 31, 2013 Investment Management Funds	Mar. 31, 2013 Trading Liabilities Derivative liabilities		Mar. 31, 2012 Trading Liabilities Derivative liabilities		Mar. 31, 2012 Trading Liabilities Liabilities, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	$ 5															$ 5	[1]
Fair value measurements for assets using significant unobservable inputs
Beginning Balance	271	365	42	[1]	45		45			3		48		63		58	[1]	97	[1]	120		157			44
Total gains or (losses) for the period included in earnings (or changes in net assets)	(14)	28			(1)	[2]		[2]		3	[2]	3	[3]	3	[3]	(11)	[1],[3]	25	[1],[3]	(5)	[4]	(3)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	3																[1]			3
Sales	(46)	(6)										(40)		(2)					[1]	(6)		(4)
Settlements	10				2												[1]			8
Ending Balance	209	324	42	[1]	44		43			0		11		58				72	[1]	112		151			44
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	(28)												(3)		0	[1]			0			(25)	[1]
Fair value measurements for liabilities using significant unobservable inputs
Beginning Balance	224																									224	[5]	314	[3]	314
Included in earnings (or changes in net liabilities)	(56)																									(56)	[3],[5]	(68)	[3],[6]	(68)
Settlements	(2)																									(2)	[5]
Ending Balance	170																									170	[5]	246	[3]	246
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	$ (27)																									$ (27)	[5]	$ (51)	[3]	$ (51)

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

[2] 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).

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

[4] Reported in investment and other income.

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

[6] (b)Reported in foreign exchange and other trading revenue.