Investments - Gross unrealized losses by unrealized loss position and credit quality (Details) - USD ($)	Mar. 31, 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	$ (1,669,000,000)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(153,000,000)
Total unrealized losses	1,822,000,000	$ 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	(296,000,000)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(110,000,000)
Total unrealized losses	406,000,000	559,000,000
Unrealized losses having loss of less than twenty percent	(41,000,000)
Unrealized losses	104,000,000
Fixed income securities
Investments [Line Items]
Fixed income securities with unrealized loss position less than 20% of amortized cost, net	(1,965,000,000)
Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net	(263,000,000)
Total unrealized losses	$ 2,228,000,000	$ 2,977,000,000