Mortgage Servicing Rights ("MSRs") and Related Liabilities - UPB related to owned MSRs (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Owned Service Loans [Line Items]
Fair Value	$ 3,485
Mortgage servicing rights
Owned Service Loans [Line Items]
UPB	274,486
Fair Value	3,485
Credit sensitive | Mortgage servicing rights
Owned Service Loans [Line Items]
UPB	144,697
Fair Value	1,652
Interest sensitive | Mortgage servicing rights
Owned Service Loans [Line Items]
UPB	129,789
Fair Value	$ 1,833
Predecessor
Owned Service Loans [Line Items]
Fair Value		$ 2,937
Predecessor | Mortgage servicing rights
Owned Service Loans [Line Items]
UPB		281,380
Fair Value		2,937
Predecessor | Credit sensitive | Mortgage servicing rights
Owned Service Loans [Line Items]
UPB		167,605
Fair Value		1,572
Predecessor | Interest sensitive | Mortgage servicing rights
Owned Service Loans [Line Items]
UPB		113,775
Fair Value		$ 1,365