Mortgage Servicing Rights and Related Liabilities - Servicing Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Transfers and Servicing [Abstract]
Contractually specified servicing fees(1)	$ 275	$ 285	$ 551	$ 582
Other service-related income(1)	214	62	359	111
Incentive and modification income(1)	14	8	28	18
Late fees(1)	16	20	34	47
Mark-to-market adjustments(2)	(180)	(261)	174	(644)
Counterparty revenue share(3)	(76)	(88)	(159)	(164)
Amortization, net of accretion(4)	(158)	(107)	(314)	(191)
Total revenues - Servicing	105	(81)	673	(241)
Cumulative incurred losses related to advances and other receivables associated with inactive and liquidated loans	8	3	20	13
Servicing fee income accretion expense	$ 70	$ 79	$ 146	$ 147