Contracts Accounted for as Insurance - Gross Premium Receivable Net of Commissions on Assumed Business Roll Forward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Gross Premium Receivable Net of Ceding Commissions [Roll Forward]
Beginning of year	$ 1,551	$ 1,468
Less: Specialty insurance premium receivable	1	1
Financial guaranty insurance premiums receivable	1,550	1,467
New business and supplemental premiums, net of commissions	39	63
Gross premiums received, net of commissions	(58)	(75)
Adjustments:
Changes in the expected term and debt service assumptions	(5)	(3)
Accretion of discount, net of commissions on assumed business	8	7
Foreign exchange gain (loss) on remeasurement	33	(10)
Financial guaranty insurance premiums receivable	1,567	1,449
Specialty insurance premium receivable	1	1
Ending balance	$ 1,568	$ 1,450