Quarterly report pursuant to Section 13 or 15(d)

MORTGAGE LOAN SALES AND SERVICING RIGHTS MORTGAGE LOAN SALES AND SERVICING RIGHTS - Residential Mortgage Portfolio, MSRs Fair Value Method Key Assumptions (Details)

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MORTGAGE LOAN SALES AND SERVICING RIGHTS MORTGAGE LOAN SALES AND SERVICING RIGHTS - Residential Mortgage Portfolio, MSRs Fair Value Method Key Assumptions (Details) - Fair value method - Residential Mortgage - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2020
Dec. 31, 2019
Dec. 31, 2017
Servicing Assets at Fair Value [Line Items]      
Constant prepayment rate (annualized), actual 17.83% 8.21%  
Constant prepayment rate (annualized), 10% adverse change $ (9) $ 0  
Constant prepayment rate (annualized), 20% adverse change (17) 0  
Spread over forward interest rate swap rates, 10% adverse change (4) $ 0  
Spread over forward interest rate swap rates, 20% adverse change $ (8)   $ 0