Investments - Carrying value for limited partnership interests (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	$ 7,907	$ 8,018
EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	6,589	6,487
Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	1,318	1,531
Private equity
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	6,567	6,339
Private equity | EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	5,287	4,905
Private equity | Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	1,280	1,434
Real estate
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	919	920
Real estate | EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	881	823
Real estate | Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	38	97
Other
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	421	759
Other | EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	421	759
Other | Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	$ 0	$ 0