Fair Value Measurements Using Significant Unobservable Inputs (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended					3 Months Ended							3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012 Available-for-sale State And Political Subdivisions	Mar. 31, 2011 Available-for-sale State And Political Subdivisions	Dec. 31, 2010 Available-for-sale State And Political Subdivisions	Mar. 31, 2012 Available-for-sale Other Debt Securities		Mar. 31, 2011 Available-for-sale Other Debt Securities	Mar. 31, 2012 Trading Assets Debt and equity instruments		Mar. 31, 2011 Trading Assets Debt and equity instruments	Dec. 31, 2010 Trading Assets Debt and equity instruments	Mar. 31, 2012 Trading Assets Derivative assets		Mar. 31, 2011 Trading Assets Derivative assets		Mar. 31, 2011 Loans	Mar. 31, 2012 Other Assets		Mar. 31, 2011 Other Assets		Mar. 31, 2011 Trading Liabilities Debt and equity instruments	Mar. 31, 2012 Trading Liabilities Derivative liabilities		Mar. 31, 2011 Trading Liabilities Derivative liabilities		Mar. 31, 2011 Other Liabilities	Dec. 31, 2010 Other Liabilities
Fair value measurements for assets using significant unobservable inputs
Beginning Balance	$ 365	$ 338	$ 45	$ 10	$ 10	$ 3		$ 58	$ 63		$ 32	$ 32	$ 97		$ 119		$ 6	$ 157		$ 113
Transfers into Level 3		7						6							1
Transfers out of Level 3		16													14		2
Total gains or (losses) for the period included in earnings (or changes in net assets)	(28)	31				(3)	[1]		(3)	[2]			(25)	[2]	25	[2]		3	[3]	6	[3]
Purchases	3	1																3		1
Sales	(6)								(2)									(4)
Settlements	(10)		(2)															(8)
Ending Balance	324	361	43	10	10			64	58		32	32	72		131		4	151		120
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	(28)	38							(3)				(25)		38
Fair value measurements for liabilities using significant unobservable inputs
Beginning Balance	314	179																				6	314		171		2	2
Total (gains) or losses for the period included in earnings (or changes in net assets)	(68)	(49)																					(68)	[2]	(49)	[2]
Settlements		(2)																				(6)			4
Ending Balance	246	128																					246		126		2	2
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	$ (51)	$ (19)																					$ (51)		$ (19)

[1] 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).

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

[3] Reported in investment income.