Mortgage Servicing Rights and Related Liabilities - Servicing Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Transfers and Servicing [Abstract]
Contractually specified servicing fees(1)	$ 280	$ 282	$ 831	$ 864
Other service-related income(1)	158	60	517	171
Incentive and modification income(1)	10	12	38	30
Late fees(1)	19	18	53	65
Mark-to-market adjustments(2)	151	(16)	376	(618)
Amortization, net of accretion(3)	(202)	(129)	(567)	(362)
Other(4)	(65)	(104)	(224)	(268)
Total revenues - Servicing	351	123	1,024	(118)
Cumulative incurred losses related to advances and other receivables associated with inactive and liquidated loans	8	7	28	20
Servicing fee income accretion expense	$ 59	$ 96	$ 205	$ 243