Fair Value Measurements Using Significant Unobservable Inputs (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended				3 Months Ended	6 Months Ended			3 Months Ended			6 Months Ended		3 Months Ended				6 Months Ended				3 Months Ended	6 Months Ended	3 Months Ended				6 Months Ended					3 Months Ended				6 Months Ended				3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Available-for-sale State And Political Subdivisions	Jun. 30, 2012 Available-for-sale State And Political Subdivisions	Jun. 30, 2011 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	Jun. 30, 2011 Available-for-sale Other Debt Securities	Jun. 30, 2012 Available-for-sale Other Debt Securities		Jun. 30, 2011 Available-for-sale Other Debt Securities	Jun. 30, 2012 Trading Assets Debt and equity instruments		Jun. 30, 2011 Trading Assets Debt and equity instruments	Jun. 30, 2012 Trading Assets Debt and equity instruments	Jun. 30, 2011 Trading Assets Debt and equity instruments	Jun. 30, 2012 Trading Assets Derivative assets		Jun. 30, 2011 Trading Assets Derivative assets		Jun. 30, 2012 Trading Assets Derivative assets		Jun. 30, 2011 Trading Assets Derivative assets		Jun. 30, 2011 Loans	Jun. 30, 2011 Loans	Jun. 30, 2012 Other Assets		Jun. 30, 2011 Other Assets		Jun. 30, 2012 Other Assets		Jun. 30, 2011 Other Assets		Jun. 30, 2011 Trading Liabilities Debt and equity instruments	Jun. 30, 2012 Trading Liabilities Derivative liabilities		Jun. 30, 2011 Trading Liabilities Derivative liabilities		Jun. 30, 2012 Trading Liabilities Derivative liabilities		Jun. 30, 2011 Trading Liabilities Derivative liabilities		Jun. 30, 2011 Other Liabilities	Jun. 30, 2011 Other Liabilities
Fair value measurements for assets using significant unobservable inputs
Beginning Balance	$ 324	$ 361	$ 365	$ 338	$ 43	$ 45	$ 10	$ 10	$ 10	$ 64	$ 3		$ 58	$ 58		$ 32	$ 63	$ 32	$ 72	[1]	$ 131	[1]	$ 97	[1]	$ 119	[1]	$ 4	$ 6	$ 151		$ 120		$ 157		$ 113
Transfers into Level 3		31		38						2			8			27		27			2	[1]			3	[1]
Transfers out of Level 3		(52)		(68)												(23)		(23)			(29)	[1]			(43)	[1]		(2)
Included in earnings (or changes in net assets)	2		(26)	31							(3)	[2]		3	[3]				1	[1],[3]	4	[1],[3]	(24)	[1],[3]	29	[1],[3]			(2)	[4]	(4)	[4]	1	[4]	2	[4]
Purchases	2		5	1																									2				5		1
Issuances		1		1																							1	1
Sales	(14)		(20)											(1)			(3)												(13)				(17)
Settlements	(1)	(1)	(11)	(1)	(1)	(3)															(1)	[1]			(1)	[1]							(8)
Ending Balance	313	340	313	340	42	42	10	10	10	66			66	60		36	60	36	73	[1]	107	[1]	73	[1]	107	[1]	5	5	138		116		138		116
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	6	7	(7)	39										2					4	[1]	7	[1]	(7)	[1]	39	[1]
Fair value measurements for liabilities using significant unobservable inputs
Beginning Balance	246	128	314	179																																	6	246	[5]	126	[5]	314	[5]	171	[5]	2	2
Transfer into Level 3		1		1																																				1	[5]			1	[5]
Total (gains) or losses for the period included in earnings (or changes in net liabilities)	56	35	(12)	(6)																																		56	[3],[5]	37	[3],[5]	(12)	[3],[5]	(4)	[3],[5]	(2)	(2)
Settlements		(9)		(19)																																	(6)			(9)	[5]			(13)	[5]
Ending Balance	302	155	302	155																																		302	[5]	155	[5]	302	[5]	155	[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	$ 66	$ 43	$ (8)	$ 17																																		$ 66	[5]	$ 45	[5]	$ (8)	[5]	$ 19	[5]	$ (2)	$ (2)

[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.