Separate accounts (Separate account liabilities rollforward) (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2025	Sep. 30, 2024
Separate Account, Liability [Line Items]
Separate Account, Liability, Beginning Balance		$ 6,231	$ 5,573
Separate Account, Liability, Premium and Deposit		1,081	945
Separate Account, Liability, Policy Charge		(122)	(118)
Separate Account, Liability, Surrender and Withdrawal		(745)	(666)
Separate Account, Liability, Benefit Payment		(345)	(320)
Separate Account, Liability, Increase (Decrease) from Invested Performance		320	625
Separate Account, Liability, Increase (Decrease) from Other Change		390	(43)
Separate Account, Liability, Ending Balance		6,810	5,996
Separate Account, Liability, Cash Surrender Value, Amount	[1]	$ 6,327	$ 5,790

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