Investments - Carrying value for limited partnership interests (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	$ 8,018	$ 4,563
EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	6,487	3,501
Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	1,531	1,062
Private equity
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	6,339	3,655
Private equity | EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	4,905	2,667
Private equity | Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	1,434	988
Real estate
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	920	697
Real estate | EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	823	623
Real estate | Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	97	74
Other investments
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	759	211
Other investments | EMA
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	759	211
Other investments | Fair Value
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	$ 0	$ 0