Loans (Details 4) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Summary of troubled debt restructurings loans and the related credit loss reserves for troubled debt restructurings loans
TDR Loans	$ 1,168	$ 1,102
Allowance for credit losses for TDR Loans
Allowance for credit losses on TDR Loans	132	121
Commercial loans [Member]
Summary of troubled debt restructurings loans and the related credit loss reserves for troubled debt restructurings loans
TDR Loans	473	473
Allowance for credit losses for TDR Loans
Allowance for credit losses on TDR Loans	29	20
Commercial loans [Member] | Construction and other real estate [Member]
Summary of troubled debt restructurings loans and the related credit loss reserves for troubled debt restructurings loans
TDR Loans	353	342
Allowance for credit losses for TDR Loans
Allowance for credit losses on TDR Loans	26	17
Commercial loans [Member] | Business banking and middle markets enterprises [Member]
Summary of troubled debt restructurings loans and the related credit loss reserves for troubled debt restructurings loans
TDR Loans	86	94
Allowance for credit losses for TDR Loans
Allowance for credit losses on TDR Loans	3	3
Commercial loans [Member] | Global banking [Member]
Summary of troubled debt restructurings loans and the related credit loss reserves for troubled debt restructurings loans
TDR Loans
Allowance for credit losses for TDR Loans
Allowance for credit losses on TDR Loans
Commercial loans [Member] | Other commercial [Member]
Summary of troubled debt restructurings loans and the related credit loss reserves for troubled debt restructurings loans
TDR Loans	34	37
Allowance for credit losses for TDR Loans
Allowance for credit losses on TDR Loans
Consumer loans [Member]
Summary of troubled debt restructurings loans and the related credit loss reserves for troubled debt restructurings loans
TDR Loans	695	629
Allowance for credit losses for TDR Loans
Allowance for credit losses on TDR Loans	103	101
Consumer loans [Member] | Residential mortgages [Member]
Summary of troubled debt restructurings loans and the related credit loss reserves for troubled debt restructurings loans
TDR Loans	677	608
Allowance for credit losses for TDR Loans
Allowance for credit losses on TDR Loans	97	94
Consumer loans [Member] | Credit cards [Member]
Summary of troubled debt restructurings loans and the related credit loss reserves for troubled debt restructurings loans
TDR Loans	18	21
Allowance for credit losses for TDR Loans
Allowance for credit losses on TDR Loans	$ 6	$ 7