Mortgage Servicing Rights and Related Liabilities - Servicing Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Transfers and Servicing [Abstract]
Contractually specified servicing fees	$ 285	$ 307	$ 582	$ 588
Other service-related income	62	32	111	82
Incentive and modification income	8	10	18	17
Late fees	20	27	47	52
Reverse servicing fees	7	8	13	17
Mark-to-market adjustments	(261)	(231)	(644)	(524)
Counterparty revenue share	(88)	(70)	(164)	(118)
Amortization, net of accretion	(102)	(56)	(178)	(79)
Total revenues - Servicing	(69)	27	(215)	35
Cumulative incurred losses related to advances and other receivables associated with inactive and liquidated loans	3	17	13	28
Servicing fee income accretion expense	79	59	147	95
Accretion of MSL	$ 5	$ 11	$ 13	$ 29