Mortgage Servicing Rights and Related Liabilities - Servicing Fees (Details) - USD ($) $ in Millions	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]
Contractually specified servicing fees	$ 421
Other service-related income	44
Incentive and modification income	17
Late fees	34
Reverse servicing fees	16
Mark-to-market adjustments	(164)
Counterparty revenue share	(68)
Amortization, net of accretion	(64)
Total servicing revenue	236
Losses for inactive and liquidated loans that are no longer part of the MSR portfolio	25	$ 38	$ 72	$ 81
Accretion expense	53	78	161	200
MSL accretion	$ 15
Predecessor
Servicing Assets at Fair Value [Line Items]
Contractually specified servicing fees		574	1,003	1,045
Other service-related income		66	168	245
Incentive and modification income		37	80	113
Late fees		53	89	82
Reverse servicing fees		37	58	57
Mark-to-market adjustments		196	(160)	(177)
Counterparty revenue share		(111)	(230)	(298)
Amortization, net of accretion		(112)	(242)	(314)
Total servicing revenue		$ 740	$ 766	$ 753