Segment Information - Financial Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Revenues:
Service related, net	$ 402	$ 460	$ 663	$ 1,215
Net gain on mortgage loans held for sale	84	139	153	436
Total revenues	486	599	816	1,651
Total expenses	278	328	539	666
Other income (expenses)
Interest income	117	50	202	86
Interest expense	(122)	(111)	(232)	(217)
Other expense, net	(5)	(5)	(14)	217
Total other income (expenses), net	(10)	(66)	(44)	86
Income before income tax expense	198	205	233	1,071
Depreciation and amortization for property and equipment and intangible assets	9	9	18	20
Total assets	13,144	12,895	13,144	12,895	$ 12,776
Operating Segments | Servicing
Revenues:
Service related, net	365	414	596	1,115
Net gain on mortgage loans held for sale	3	(19)	3	(4)
Total revenues	368	395	599	1,111
Total expenses	159	143	312	265
Other income (expenses)
Interest income	107	35	186	54
Interest expense	(73)	(61)	(136)	(115)
Other expense, net	0	0	0	0
Total other income (expenses), net	34	(26)	50	(61)
Income before income tax expense	243	226	337	785
Depreciation and amortization for property and equipment and intangible assets	3	5	5	10
Total assets	10,231	9,645	10,231	9,645
Operating Segments | Originations
Revenues:
Service related, net	16	24	27	66
Net gain on mortgage loans held for sale	81	158	150	440
Total revenues	97	182	177	506
Total expenses	59	125	115	299
Other income (expenses)
Interest income	10	15	16	32
Interest expense	(10)	(10)	(17)	(22)
Other expense, net	0	0	0	0
Total other income (expenses), net	0	5	(1)	10
Income before income tax expense	38	62	61	217
Depreciation and amortization for property and equipment and intangible assets	2	5	4	9
Total assets	1,086	1,381	1,086	1,381
Corporate/Other
Revenues:
Service related, net	21	22	40	34
Net gain on mortgage loans held for sale	0	0	0	0
Total revenues	21	22	40	34
Total expenses	60	60	112	102
Other income (expenses)
Interest income	0	0	0	0
Interest expense	(39)	(40)	(79)	(80)
Other expense, net	(5)	(5)	(14)	217
Total other income (expenses), net	(44)	(45)	(93)	137
Income before income tax expense	(83)	(83)	(165)	69
Depreciation and amortization for property and equipment and intangible assets	4	(1)	9	1
Total assets	$ 1,827	$ 1,869	$ 1,827	$ 1,869