Investments - Carrying value for limited partnership interests (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	$ 7,943	$ 8,018
EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	6,548	6,487
Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	1,395	1,531
Private equity
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	6,578	6,339
Private equity | EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	5,224	4,905
Private equity | Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	1,354	1,434
Real estate
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	928	920
Real estate | EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	887	823
Real estate | Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	41	97
Other
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	437	759
Other | EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	437	759
Other | Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	$ 0	$ 0