Investments - Carrying value for limited partnership interests (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	$ 7,977	$ 8,018
EMA limited partnerships
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	6,487	6,487
Limited partnership interests
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	1,490	1,531
Private equity
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	6,520	6,339
Private equity | EMA limited partnerships
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	5,127	4,905
Private equity | Limited partnership interests
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	1,393	1,434
Real estate
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	956	920
Real estate | EMA limited partnerships
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	859	823
Real estate | Limited partnership interests
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	97	97
Other investments
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	501	759
Other investments | EMA limited partnerships
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	501	759
Other investments | Limited partnership interests
Debt and Equity Securities, FV-NI [Line Items]
Limited partnership interests	$ 0	$ 0