Investments - Schedule of Gross Unrealized Losses by Unrealized Loss Position and Credit Quality (Details) - USD ($) $ in Millions	Sep. 30, 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	$ (546)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(12)
Total unrealized losses	(558)	$ (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	(64)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(7)
Total unrealized losses	(71)	(200)
Fixed income securities
Investments [Line Items]
Fixed income securities with unrealized loss position less than 20% of amortized cost, net	(610)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(19)
Total unrealized losses	$ (629)	$ (1,434)