Mortgage Loans Held for Sale and Investment - Reconciliation to Cash Flow (Details) - USD ($) $ in Millions	5 Months Ended	7 Months Ended	12 Months Ended
	Dec. 31, 2018	Jul. 31, 2018	Dec. 31, 2017
Loans Receivable Held-for-sale, Net, Reconciliation to Cash Flow [Roll Forward]
Balance - beginning of period	$ 1,514
Mortgage loans originated and purchased, net of fees	8,890
Loans sold	(9,304)
Repurchase of loans out of Ginnie Mae securitizations	527
Transfer of mortgage loans held for sale to claims receivable in advances and other receivables	(5)
Net transfer of mortgage loans held for sale (to)/from REO in other assets	5
Changes in fair value	6
Other purchase-related activities	(2)
Balance - end of period	1,631	$ 1,514
Predecessor
Loans Receivable Held-for-sale, Net, Reconciliation to Cash Flow [Roll Forward]
Balance - beginning of period	$ 1,514	1,891	$ 1,788
Mortgage loans originated and purchased, net of fees		12,319	19,140
Loans sold		(13,255)	(20,318)
Repurchase of loans out of Ginnie Mae securitizations		544	1,249
Transfer of mortgage loans held for sale to claims receivable in advances and other receivables		(7)	(19)
Net transfer of mortgage loans held for sale (to)/from REO in other assets		14	23
Changes in fair value		(1)	9
Other purchase-related activities		9	19
Balance - end of period		$ 1,514	$ 1,891