Goodwill and Intangible Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Goodwill [Line Items]
Goodwill	$ 141	$ 141	$ 120
Addition from acquisitions(1)		21
Impairment of goodwill		0	0
Amortization expense		7	6
Impairment of technology and intangible assets		0	0
Rushmore
Goodwill [Line Items]
Payments to Acquire Intangible Assets		23
Roosevelt [Member]
Goodwill [Line Items]
Addition from acquisitions(1)	21
Payments to Acquire Intangible Assets		4
Servicing
Goodwill [Line Items]
Goodwill	85	85	80
Addition from acquisitions(1)		5
Servicing | Roosevelt [Member]
Goodwill [Line Items]
Addition from acquisitions(1)		5
Originations
Goodwill [Line Items]
Goodwill	28	28	28
Addition from acquisitions(1)		0
Corporate/Other(2)
Goodwill [Line Items]
Goodwill	$ 28	28	$ 12
Addition from acquisitions(1)		16
Corporate/Other(2) | Roosevelt [Member]
Goodwill [Line Items]
Addition from acquisitions(1)		$ 16