Mortgage Servicing Rights ("MSRs") and Related Liabilities - UPB related to owned MSRs (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Owned Service Loans [Line Items]
Fair Value	$ 3,109	$ 3,496
Mortgage servicing rights
Owned Service Loans [Line Items]
UPB	290,634	296,782
Fair Value	3,109	3,496
Credit sensitive | Mortgage servicing rights
Owned Service Loans [Line Items]
UPB	138,726	147,895
Fair Value	1,386	1,613
Interest sensitive | Mortgage servicing rights
Owned Service Loans [Line Items]
UPB	151,908	148,887
Fair Value	1,723	1,883
Agency(1) | Mortgage servicing rights
Owned Service Loans [Line Items]
UPB	238,956	240,688
Fair Value	2,618	2,944
Non-agency(2) | Mortgage servicing rights
Owned Service Loans [Line Items]
UPB	51,678	56,094
Fair Value	$ 491	$ 552