Loans and asset quality- Information about Impaired Loans (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance, average recorded investment	$ 32		$ 34		$ 102
Impaired loans without an allowance, average recorded investment	3	[1]	5	[1]	13	[1]
Total impaired loans, average recorded investment	35		39		115
Impaired loans with an allowance, interest income recognized	0		0		1
Impaired loans without an allowance, interest income recognized	0	[1]	0	[1]	0	[1]
Total impaired loans, interest income recognized	0		0		1
Impaired loans with an allowance, recorded investment	31		32
Impaired loans without an allowance, recorded investment	(2)	[1]	(4)	[1]
Total impaired loans, recorded investment	33	[2]	36	[2]
Impaired loans with an allowance, unpaid Principal balance	36		50
Impaired loans without an allowance, unpaid Principal balance	3	[1]	4	[1]
Total impaired loans, unpaid Principal balance	39	[2]	54	[2]
Impaired loans with an allowance, related allowance	8	[2],[3]	7	[2],[3]
Commercial
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance, average recorded investment	14		15		56
Impaired loans without an allowance, average recorded investment	0		0		0
Impaired loans with an allowance, interest income recognized	0		0		1
Impaired loans without an allowance, interest income recognized	0		0		0
Impaired loans with an allowance, recorded investment	13		15
Impaired loans with an allowance, unpaid Principal balance	13		20
Impaired loans with an allowance, related allowance	3	[3]	2	[3]
Commercial real estate
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance, average recorded investment	3		2		9
Impaired loans without an allowance, average recorded investment	1		1		8
Impaired loans with an allowance, interest income recognized	0		0		0
Impaired loans without an allowance, interest income recognized	0		0		0
Impaired loans with an allowance, recorded investment	2		2
Impaired loans without an allowance, recorded investment	(1)		(1)
Impaired loans with an allowance, unpaid Principal balance	3		4
Impaired loans without an allowance, unpaid Principal balance	2		1
Impaired loans with an allowance, related allowance	1	[3]	1	[3]
Financial institutions
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance, average recorded investment	0		0		1
Impaired loans without an allowance, average recorded investment	0		1		1
Impaired loans with an allowance, interest income recognized	0		0		0
Impaired loans without an allowance, interest income recognized	0		0		0
Impaired loans with an allowance, recorded investment	0		0
Impaired loans without an allowance, recorded investment	0		0
Impaired loans with an allowance, unpaid Principal balance	0		0
Impaired loans without an allowance, unpaid Principal balance	0		0
Impaired loans with an allowance, related allowance	0	[3]	0	[3]
Wealth management loans and mortgages
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance, average recorded investment	9		10		27
Impaired loans without an allowance, average recorded investment	2		3		4
Impaired loans with an allowance, interest income recognized	0		0		0
Impaired loans without an allowance, interest income recognized	0		0		0
Impaired loans with an allowance, recorded investment	9		9
Impaired loans without an allowance, recorded investment	(1)		3
Impaired loans with an allowance, unpaid Principal balance	9		9
Impaired loans without an allowance, unpaid Principal balance	1		3
Impaired loans with an allowance, related allowance	2	[3]	3	[3]
Foreign
Financing Receivable, Impaired [Line Items]
Impaired loans with an allowance, average recorded investment	6		7		9
Impaired loans with an allowance, interest income recognized	0		0		0
Impaired loans with an allowance, recorded investment	7		6
Impaired loans with an allowance, unpaid Principal balance	11		17
Impaired loans with an allowance, related allowance	$ 2	[3]	$ 1	[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 less than $1 million of impaired loans in amounts individually less than $1 million at both March 31, 2014 and Dec. 31, 2013. The allowance for loan loss associated with these loans totaled less than $1 million at both March 31, 2014 and Dec. 31, 2013.

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