Information about Impaired Loans (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Dec. 31, 2011		Mar. 31, 2011
Financing Receivable, Impaired [Line Items]
Average recorded investment	$ 144		$ 117		$ 137
Interest income recognized	1		1
Recorded investment	159	[1]	128	[1]
Unpaid Principal balance	183	[1]	153	[1]
Related allowance	38	[1],[2]	32	[1],[2]
Impaired Financing Receivables with Related Allowance
Financing Receivable, Impaired [Line Items]
Average recorded investment	135		105		115
Interest income recognized	1		1
Recorded investment	150		119
Unpaid Principal balance	168		138
Related allowance	38	[2]	32	[2]
Impaired Financing Receivables with Related Allowance | Commercial
Financing Receivable, Impaired [Line Items]
Average recorded investment	46		26		28
Interest income recognized	1		1
Recorded investment	66	[2]	26	[2]
Unpaid Principal balance	70	[2]	31	[2]
Related allowance	17	[2]	9	[2]
Impaired Financing Receivables with Related Allowance | Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Average recorded investment	35		25		24
Recorded investment	35		35
Unpaid Principal balance	41		41
Related allowance	6	[2]	7	[2]
Impaired Financing Receivables with Related Allowance | Financial Institutions
Financing Receivable, Impaired [Line Items]
Average recorded investment	16		17		4
Recorded investment	11		21
Unpaid Principal balance	11		21
Related allowance	5	[2]	7	[2]
Impaired Financing Receivables with Related Allowance | Wealth Management Loans and Mortgages
Financing Receivable, Impaired [Line Items]
Average recorded investment	28		26		52
Recorded investment	28		27
Unpaid Principal balance	28		27
Related allowance	7	[2]	5	[2]
Impaired Financing Receivables with Related Allowance | Foreign
Financing Receivable, Impaired [Line Items]
Average recorded investment	10		11		7
Recorded investment	10		10
Unpaid Principal balance	18		18
Related allowance	3	[2]	4	[2]
Impaired Financing Receivables with No Related Allowance
Financing Receivable, Impaired [Line Items]
Average recorded investment	9	[3]	12	[3]	22	[3]
Recorded investment	9	[3]	9	[3]
Unpaid Principal balance	15	[3]	15	[3]
Impaired Financing Receivables with No Related Allowance | Commercial
Financing Receivable, Impaired [Line Items]
Average recorded investment					4
Impaired Financing Receivables with No Related Allowance | Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Average recorded investment	3		8		17
Recorded investment	3		3
Unpaid Principal balance	3		3
Impaired Financing Receivables with No Related Allowance | Financial Institutions
Financing Receivable, Impaired [Line Items]
Average recorded investment	3		1
Recorded investment	3		3
Unpaid Principal balance	9		9
Impaired Financing Receivables with No Related Allowance | Wealth Management Loans and Mortgages
Financing Receivable, Impaired [Line Items]
Average recorded investment	3		3		1
Recorded investment	3		3
Unpaid Principal balance	$ 3		$ 3

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

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

[3] 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.