Investments - Debt Securities by Maturity (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Net Amortized Cost
Less than one year	$ 1,273
One year through five years	7,413
After five years through ten years	4,279
Greater than ten years	4,106
Net Amortized Cost	22,101	$ 22,063
Fair Value
Less than one year	1,254
One year through five years	6,995
After five years through ten years	3,891
Greater than ten years	3,518
Total	20,401	20,280
Residential mortgage-backed securities
Net Amortized Cost
Debt securities, maturity, without single maturity date	833
Net Amortized Cost	833	845
Fair Value
Debt securities, maturity, without single maturity date	730
Total	730	757
Commercial mortgage-backed securities
Net Amortized Cost
Debt securities, maturity, without single maturity date	1,128
Net Amortized Cost	1,128	1,172
Fair Value
Debt securities, maturity, without single maturity date	977
Total	977	1,018
Other asset-backed securities
Net Amortized Cost
Debt securities, maturity, without single maturity date	3,069
Net Amortized Cost	3,069	2,940
Fair Value
Debt securities, maturity, without single maturity date	3,036
Total	$ 3,036	$ 2,810