Loans (Details 9) (Commercial loans [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Financing Receivable, Modifications [Line Items]
Impaired commercial loans as TDR	$ 473	$ 473
Construction and other real estate [Member]
Financing Receivable, Modifications [Line Items]
Impaired commercial loans as TDR	353	342
Business banking and middle markets enterprises [Member]
Financing Receivable, Modifications [Line Items]
Impaired commercial loans as TDR	86	94
Global banking [Member]
Financing Receivable, Modifications [Line Items]
Impaired commercial loans as TDR
Other commercial [Member]
Financing Receivable, Modifications [Line Items]
Impaired commercial loans as TDR	$ 34	$ 37