Investments - Summary of Fair Value, Including Financial Guarantee, and Weighted-Average Underlying Rating, Excluding Financial Guarantee, of Insured Securities (Details) - Standard & Poor's, B- Rating [Member] - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	$ 421	$ 482
Municipal Bonds [Member]
Schedule of Investments [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	$ 8	$ 9