Investments - Summary of Fair Value, Including Financial Guarantee, and Weighted-Average Underlying Rating, Excluding Financial Guarantee, of Insured Securities (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Standard & Poor's, B Rating [Member]
Schedule of Investments [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		$ 482
Standard & Poor's, B- Rating [Member]
Schedule of Investments [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	$ 406
Municipal Bonds [Member] | Standard & Poor's, B Rating [Member]
Schedule of Investments [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		$ 9
Municipal Bonds [Member] | Standard & Poor's, B- Rating [Member]
Schedule of Investments [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	$ 9