Separate accounts (Liabilities) (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022
Separate Account, Liability, Surrender and Withdrawal [Abstract]
Separate Account, Liability, Beginning Balance		$ 5,190	$ 5,560
Acquisition of Cigna		0	301
Separate Account, Liability, Premium and Deposit		724	1,147
Separate Account, Liability, Policy Charge		(103)	(93)
Separate Account, Liability, Surrender and Withdrawal		(407)	(304)
Separate Account, Liability, Benefit Payment		(291)	(289)
Separate Account, Liability, Increase (Decrease) from Invested Performance		382	(978)
Separate Account, Liability, Increase (Decrease) from Other Change		(189)	(453)
Separate Account, Liability, Ending Balance		5,306	4,891
Separate Account, Liability, Cash Surrender Value, Amount	[1]	$ 5,285	$ 4,771

[1] Cash surrender value represents the amount of the contract holder's account balances distributable at the balance sheet date less certain surrender charges.