Advances and Other Receivables - Schedule of Accounts Receivable (Details) - USD ($) $ in Millions	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Receivables [Abstract]
Servicing advances, net of $30 and $72 purchase discount, respectively	$ 893		$ 975
Receivables from agencies, investors and prior servicers, net of $13 and $21 purchase discount, respectively	188		173
Reserves	(172)		(208)
Total advances and other receivables, net	909		940
Servicing advances discount	30	$ 31	72	$ 92	$ 117	$ 131
Receivables discount	$ 13	$ 20	$ 21	$ 21	$ 21	$ 21