Separate accounts (Fair value of assets) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 5,573	$ 5,190	$ 5,560
Separate Account, Cash and Cash Equivalents
Fair Value, Separate Account Investment [Line Items]
Separate account assets	65	141	165
Separate Account, equity securities and mutual funds
Fair Value, Separate Account Investment [Line Items]
Separate account assets	5,417	4,960	5,296
Separate Account, Non-U.S. Government Treasuries
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 91	$ 89	$ 99