Quarterly report pursuant to Section 13 or 15(d)

LOAN SALES AND SECURITIZATIONS - Automobile Loans, MSRs Amortization Method (Details)

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LOAN SALES AND SECURITIZATIONS - Automobile Loans, MSRs Amortization Method (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Servicing Asset at Amortized Cost, Balance [Roll Forward]      
Fair value, end of period $ 246   $ 238
Automobile      
Servicing Asset at Amortized Cost, Balance [Roll Forward]      
Carrying value, beginning of period 8 $ 18  
Amortization and other (2) (3)  
Fair value, end of period 7 15  
Carrying value, end of period $ 6 $ 15  
Automobile | Amortization method      
Servicing Asset at Amortized Cost, Balance [Roll Forward]      
Weighted-average life (years) 3 years 5 months 4 years