Mortgage Servicing Rights and Related Liabilities - Servicing Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Transfers and Servicing [Abstract]
Contractually specified servicing fees	$ 282	$ 305	$ 864	$ 893
Other service-related income	59	51	170	133
Incentive and modification income	12	12	30	29
Late fees	18	30	65	82
Reverse servicing fees	6	7	19	24
Mark-to-market adjustments	(29)	(83)	(673)	(607)
Counterparty revenue share	(104)	(86)	(268)	(204)
Amortization, net of accretion	(112)	(73)	(290)	(152)
Total revenues - Servicing	132	163	(83)	198
Cumulative incurred losses related to advances and other receivables associated with inactive and liquidated loans	7	18	20	46
Servicing fee income accretion expense	96	77	243	172
Accretion of MSL	$ 4	$ 10	$ 17	$ 39