v2.4.0.6
Securitizations and Variable Interest Entities, Key Economic Assumptions - Mortgage Servicing Assets (Details) (Residential Mortgage Servicing [Member], USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Residential Mortgage Servicing [Member]
     
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]      
Prepayment speed (annual CPR) 13.40% 12.80% 13.50%
Discount rate 7.30% 7.70% 5.40%
Cost to service ($ per loan) $ 151 $ 146 $ 151