Mortgage Loans Held for Sale and Investment - Loans Held For Sale (Details) - USD ($) $ in Millions	Dec. 31, 2018	Jul. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage loans held for sale - UPB	$ 1,568
Mark-to-market adjustment	63
Total mortgage loans held for sale	1,631	$ 1,514
UPB	45
Fair Value	42
Predecessor
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage loans held for sale - UPB			$ 1,837
Mark-to-market adjustment			54
Total mortgage loans held for sale		$ 1,514	1,891	$ 1,788
UPB			66
Fair Value			64
Ginnie Mae Repurchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
UPB	$ 40		$ 64