Investments - Schedule of Gross Unrealized Losses by Unrealized Loss Position and Credit Quality (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Investment grade fixed income securities
Investments [Line Items]
Fixed income securities with unrealized loss position less than 20% of amortized cost, net	$ (737)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(35)
Total unrealized losses	(772)	$ (1,128)
Below investment grade fixed income securities
Investments [Line Items]
Fixed income securities with unrealized loss position less than 20% of amortized cost, net	(105)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(6)
Total unrealized losses	(111)	(102)
Fixed income securities
Investments [Line Items]
Fixed income securities with unrealized loss position less than 20% of amortized cost, net	(842)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(41)
Total unrealized losses	$ (883)	$ (1,230)