Loans (Details 10) (Commercial loans [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Unpaid Principal Balance of Impaired Loans
Unpaid principal balance of impaired commercial loans	$ 981	$ 1,194
Construction and other real estate [Member]
Unpaid Principal Balance of Impaired Loans
Unpaid principal balance of impaired commercial loans	613	784
Business banking and middle markets enterprises [Member]
Unpaid Principal Balance of Impaired Loans
Unpaid principal balance of impaired commercial loans	164	180
Global banking [Member]
Unpaid Principal Balance of Impaired Loans
Unpaid principal balance of impaired commercial loans	114	137
Other commercial [Member]
Unpaid Principal Balance of Impaired Loans
Unpaid principal balance of impaired commercial loans	$ 90	$ 93