Contracts Accounted for as Insurance - Selected Information for Policies Paid In Installments (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Financial Guarantee Insurance Premiums [Line Items]
Premiums receivable, net of commissions payable	$ 1,450	$ 1,468	$ 1,346	$ 1,298
Financial Guarantee Policies Paid in Installments
Financial Guarantee Insurance Premiums [Line Items]
Premiums receivable, net of commissions payable	1,449	1,467
Deferred premium revenue	$ 1,757	$ 1,768
Weighted-average risk-free rate used to discount premiums	2.10%	2.10%
Weighted-average period of premiums receivable (in years)	12 years 4 months 24 days	12 years 6 months