Mortgage Loans Held for Sale and Investment - Narrative (Details) - USD ($)	5 Months Ended	7 Months Ended	12 Months Ended
	Dec. 31, 2018	Jul. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Servicing Assets at Fair Value [Line Items]
Mortgage loans held for sale in foreclosure	$ 33,000,000		$ 51,000,000
Sale of mortgage loans held for sale	9,397,000,000	$ 13,382,000,000	20,772,000,000	$ 21,942,000,000
Gain on sale of mortgage loans held for sale	93,000,000	127,000,000	454,000,000	$ 539,000,000
Mortgage loans held for investment in foreclosure	15,000,000		22,000,000
Ginnie Mae HECM
Servicing Assets at Fair Value [Line Items]
Delinquent loans acquired	56,000,000	118,000,000	316,000,000
Delinquent loans securitized or sold	95,000,000	151,000,000	341,000,000
Purchased loans that have re-performed	$ 70,000,000		227,000,000
Mortgage Loans Held for Investment
Servicing Assets at Fair Value [Line Items]
Reclassifications from nonaccretable discount		$ 1,000,000	$ 1,000,000