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Mortgage Servicing - Schedule of Composition of Primary Servicing and Subservicing Portfolios by Type of Property Serviced as Measured by UPB (Footnote) (Details) - USD ($)
$ in Billions
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Schedule of Servicing and Subservicing Portfolio [Line Items]      
Primary servicing unpaid principal balance $ 137.1 $ 160.8 $ 175.1