Investments - Gross unrealized losses by unrealized loss position and credit quality (Details) - USD ($)	Jun. 30, 2023	Dec. 31, 2022
Investment grade fixed income securities
Investments [Line Items]
Fixed income securities with unrealized loss position less than 20% of amortized cost, net	$ (1,884,000,000)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(182,000,000)
Total unrealized losses	2,066,000,000	$ 2,418,000,000
Below investment grade fixed income securities
Investments [Line Items]
Fixed income securities with unrealized loss position less than 20% of amortized cost, net	(300,000,000)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(91,000,000)
Total unrealized losses	391,000,000	559,000,000
Unrealized losses having loss of less than twenty percent	19,000,000
Unrealized losses	90,000,000
Fixed income securities
Investments [Line Items]
Fixed income securities with unrealized loss position less than 20% of amortized cost, net	(2,184,000,000)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(273,000,000)
Total unrealized losses	$ 2,457,000,000	$ 2,977,000,000