Contracts Accounted for as Insurance - Net Earned Premiums (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Insurance [Abstract]
Scheduled net earned premiums	$ 73	$ 73	$ 216	$ 212
Accelerations from refundings and terminations	14	14	56	26
Accretion of discount on net premiums receivable	8	7	23	20
Financial guaranty insurance net earned premiums	95	94	295	258
Specialty net earned premiums	2	1	5	3
Net earned premiums	$ 97	$ 95	$ 300	$ 261