Contracts Accounted for as Insurance - Gross Premium Receivable Net of Commissions on Assumed Business Roll Forward (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Gross Premium Receivable Net of Ceding Commissions [Roll Forward]
Beginning of year	$ 1,468	$ 1,298
Less: Specialty insurance premium receivable	1	1
Financial guaranty insurance premiums receivable	1,467	1,297
Gross written premiums on new business, net of commissions	278	215
Gross premiums received, net of commissions	(267)	(170)
Adjustments:
Changes in the expected term and debt service assumptions	(28)	4
Accretion of discount, net of commissions on assumed business	19	20
Foreign exchange gain (loss) on remeasurement	43	9
Financial guaranty insurance premiums receivable	1,512	1,375
Specialty insurance premium receivable	1	1
Ending balance	$ 1,513	$ 1,376