Loans and asset quality- Details of Loan Distribution and Industry Concentrations of Credit Risk (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 54,036		$ 51,657
Financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	13,576		14,359
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,959		1,647
Wealth management loans and mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	10,004		9,818
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,145		2,010
Other residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,346		1,385
Overdrafts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	5,583		3,715
Margin loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	16,430		15,652
Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	39,246		38,230
Domestic | Financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	4,492		4,511
Domestic | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,754		1,534
Domestic | Wealth management loans and mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	9,922		9,743
Domestic | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,128		2,001
Domestic | Lease financings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,308	[1]	1,322	[1]
Domestic | Other residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,346		1,385
Domestic | Overdrafts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,078		1,314		2,772
Domestic | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	788		768		644
Domestic | Margin loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	16,430		15,652		13,242
Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	14,790		13,427
Foreign | Financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	9,084		9,848
Foreign | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	205		113
Foreign | Wealth management loans and mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	82		75
Foreign | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	17		9
Foreign | Lease financings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	860	[1]	945	[1]
Foreign | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 4,542		$ 2,437

[1] Net of unearned income on domestic and foreign lease financings of $934 million at March 31, 2014 and $1,020 million at Dec. 31, 2013.