Mortgage Servicing Rights and Related Liabilities - Revenues for Services Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Transfers and Servicing [Abstract]
Contractually specified servicing fees	$ 1,141	$ 1,194
Other service-related income	290	182
Incentive and modification income	39	40
Late fees	83	110
Reverse servicing fees	24	31
Mark-to-market adjustments	(679)	(505)
Counterparty revenue share	(371)	(284)
Amortization, net of accretion	(420)	(236)
Total revenues - Servicing	107	532
Losses for inactive and liquidated loans that are no longer part of the MSR portfolio	28	62
Accretion expense	$ 338	$ 243