Information about Impaired Loans (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended						6 Months Ended
	Jun. 30, 2012		Mar. 31, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011		Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance, average recorded investment	$ 139		$ 135		$ 99		$ 132		$ 105
Impaired loans without an allowance, average recorded investment	8	[1]	9	[1]	18	[1]	8	[1]	19	[1]
Total impaired loans, average recorded investment	147		144		117		140		124
Impaired loans with an allowance, interest income recognized	1		1		1		2		1
Impaired loans without an allowance, interest income recognized		[1]		[1]		[1]		[1]		[1]
Total impaired loans, interest income recognized	1		1		1		2		1
Impaired loans with an allowance, recorded investment	127						127				119
Impaired loans without an allowance, recorded investment	7	[1]					7	[1]			9	[1]
Total impaired loans, recorded investment	134	[2]					134	[2]			128	[2]
Impaired loans with an allowance, unpaid Principal balance	140						140				138
Impaired loans without an allowance, unpaid Principal balance	14	[1]					14	[1]			15	[1]
Total impaired loans, unpaid Principal balance	154	[2]					154	[2]			153	[2]
Impaired loans with an allowance, related allowance	34	[2],[3]					34	[2],[3]			32	[2],[3]
Commercial
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance, average recorded investment	64		46		28		51		28
Impaired loans without an allowance, average recorded investment					2				2
Impaired loans with an allowance, interest income recognized	1		1				2
Impaired loans without an allowance, interest income recognized
Impaired loans with an allowance, recorded investment	62	[3]					62	[3]			26	[3]
Impaired loans with an allowance, unpaid Principal balance	66	[3]					66	[3]			31	[3]
Impaired loans with an allowance, related allowance	16	[3]					16	[3]			9	[3]
Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance, average recorded investment	31		35		18		32		21
Impaired loans without an allowance, average recorded investment	3		3		14		3		16
Impaired loans without an allowance, interest income recognized
Impaired loans with an allowance, recorded investment	27						27				35
Impaired loans without an allowance, recorded investment	2						2				3
Impaired loans with an allowance, unpaid Principal balance	28						28				41
Impaired loans without an allowance, unpaid Principal balance	2						2				3
Impaired loans with an allowance, related allowance	6	[3]					6	[3]			7	[3]
Financial Institutions
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance, average recorded investment	6		16		4		11		4
Impaired loans without an allowance, average recorded investment	2		3				2
Impaired loans without an allowance, interest income recognized
Impaired loans with an allowance, recorded investment	1						1				21
Impaired loans without an allowance, recorded investment	2						2				3
Impaired loans with an allowance, unpaid Principal balance	1						1				21
Impaired loans without an allowance, unpaid Principal balance	9						9				9
Impaired loans with an allowance, related allowance											7	[3]
Wealth Management Loans and Mortgages
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance, average recorded investment	28		28		39		28		43
Impaired loans without an allowance, average recorded investment	3		3		2		3		1
Impaired loans with an allowance, interest income recognized					1				1
Impaired loans without an allowance, interest income recognized
Impaired loans with an allowance, recorded investment	28						28				27
Impaired loans without an allowance, recorded investment	3						3				3
Impaired loans with an allowance, unpaid Principal balance	28						28				27
Impaired loans without an allowance, unpaid Principal balance	3						3				3
Impaired loans with an allowance, related allowance	7	[3]					7	[3]			5	[3]
Foreign
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance, average recorded investment	10		10		10		10		9
Impaired loans with an allowance, recorded investment	9						9				10
Impaired loans with an allowance, unpaid Principal balance	17						17				18
Impaired loans with an allowance, related allowance	$ 5	[3]					$ 5	[3]			$ 4	[3]

[1] When the discounted cash flows, collateral value or market price equals or exceeds the carrying value of the loan, then the loan does not require an allowance under the accounting standard related to impaired loans.

[2] Excludes an aggregate of $2 million of impaired loans in amounts individually less than $1 million at both June 30, 2012 and Dec. 31, 2011. The allowance for loan loss associated with these loans totaled less than $1 million at both June 30, 2012 and Dec. 31, 2011.

[3] The allowance for impaired loans is included in the allowance for loan losses.