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, 2019	Dec. 31, 2017
Transfers and Servicing [Abstract]
Contractually specified servicing fees	$ 421	$ 574	$ 1,194	$ 1,003
Other service-related income	44	66	182	168
Incentive and modification income	17	37	40	80
Late fees	34	53	110	89
Reverse servicing fees	16	37	31	58
Mark-to-market adjustments	(164)	196	(505)	(160)
Counterparty revenue share	(68)	(111)	(284)	(230)
Amortization, net of accretion	(64)	(112)	(236)	(242)
Total revenues - Servicing	236	740	532	766
Gain from clean-up call option			21
Losses for inactive and liquidated loans that are no longer part of the MSR portfolio	25	38	62	72
Accretion expense	53	$ 78	243	$ 161
MSL accretion	$ 15		$ 47