Loans and asset quality- Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				3 Months Ended				3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Jan. 18, 2008	Aug. 31, 2007	Mar. 31, 2014 Other residential mortgages Contract	Dec. 31, 2013 Other residential mortgages	Mar. 31, 2014 Wealth management mortgages	Dec. 31, 2013 Wealth management mortgages	Mar. 31, 2014 Wealth management mortgages New York State	Mar. 31, 2014 Wealth management mortgages California State	Mar. 31, 2014 Wealth management mortgages Massachusetts	Mar. 31, 2014 Wealth management mortgages Florida	Mar. 31, 2014 Wealth management mortgages Other	Mar. 31, 2014 Overdrafts	Dec. 31, 2013 Overdrafts	Mar. 31, 2014 Margin loans	Dec. 31, 2013 Margin loans	Mar. 31, 2014 Domestic	Dec. 31, 2013 Domestic	Mar. 31, 2014 Domestic Other residential mortgages	Dec. 31, 2013 Domestic Other residential mortgages	Mar. 31, 2014 Domestic Overdrafts	Dec. 31, 2013 Domestic Overdrafts	Mar. 31, 2013 Domestic Overdrafts	Mar. 31, 2014 Domestic Margin loans	Dec. 31, 2013 Domestic Margin loans	Mar. 31, 2013 Domestic Margin loans	Mar. 31, 2014 Domestic Margin loans Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Subsequently defaulted number of contracts (contracts)					5
Subsequently defaulted recorded investment					$ 1
Loan to value ratio at origination (percent)							64.00%
Percentage of past due mortgages (percent)							1.00%
Geographic concentrations (percent)									21.00%	21.00%	16.00%	8.00%	34.00%
Purchased mortgages																				394
Purchased residential mortgages, loan to value ratio (percent)																				76.00%
Percentage of purchased residential mortgages that were at least 60 days delinquent (percent)																				18.00%
Loans	54,036	51,657			1,346	1,385	4,928	4,834						5,583	3,715	16,430	15,652	39,246	38,230	1,346	1,385	1,078	1,314	2,772	16,430	15,652	13,242
Number of business days in which overdrafts are generally repaid	2 days													2 days
Required daily collateral margin (percent)																												100.00%
Legal Claim			$ 312	$ 312