Annual report pursuant to Section 13 and 15(d)

LOAN SALES AND SECURITIZATIONS - Residential Mortgage Portfolio, MSRs Amortization Method Assumptions (Details)

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LOAN SALES AND SECURITIZATIONS - Residential Mortgage Portfolio, MSRs Amortization Method Assumptions (Details) - Sensitivity Analysis Amortization Carrying Method - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Automobile    
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]    
Spread over forward interest rate swap rates 0.00% 5.00%
Residential Mortgage    
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]    
Constant prepayment rate (annualized) 8.30% 7.80%
Constant prepayment rate (annualized), Decline in fair value due to 10% adverse change $ 0 $ 0
Constant prepayment rate (annualized), Decline in fair value due to 20% adverse change $ 0 $ 0
Spread over forward interest rate swap rates 0.00% 9.00%
Spread over forward interest rate swap rates, Decline in fair value due to 10% adverse change $ 0 $ 0
Spread over forward interest rate swap rates, Decline in fair value due to 20% adverse change $ 0 $ 0