Investments - Schedule of Gross Unrealized Losses by Unrealized Loss Position and Credit Quality (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Investment grade fixed income securities
Investments [Line Items]
Fixed income securities with unrealized loss position less than 20% of amortized cost, net	$ (1,226)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(68)
Total unrealized losses	(1,294)	$ (1,234)
Below investment grade fixed income securities
Investments [Line Items]
Fixed income securities with unrealized loss position less than 20% of amortized cost, net	(150)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(24)
Total unrealized losses	(174)	(200)
Fixed income securities
Investments [Line Items]
Fixed income securities with unrealized loss position less than 20% of amortized cost, net	(1,376)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(92)
Total unrealized losses	$ (1,468)	$ (1,434)