Investments - Carrying value for limited partnership interests (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	$ 7,971	$ 8,114
EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	6,743	6,868
Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	1,228	1,246
Private equity
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	6,745	6,589
Private equity | EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	5,546	5,372
Private equity | Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	1,199	1,217
Real estate
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	1,048	1,042
Real estate | EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	1,019	1,013
Real estate | Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	29	29
Other
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	178	483
Other | EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	178	483
Other | Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	$ 0	$ 0