Separate accounts (Separate account liabilities rollforward) (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2025	Jun. 30, 2024
Separate Account, Liability [Line Items]
Separate Account, Liability, Beginning Balance		$ 6,231	$ 5,573
Separate Account, Liability, Premium and Deposit		802	576
Separate Account, Liability, Policy Charge		(79)	(80)
Separate Account, Liability, Surrender and Withdrawal		(494)	(426)
Separate Account, Liability, Benefit Payment		(225)	(208)
Separate Account, Liability, Increase (Decrease) from Invested Performance		(265)	502
Separate Account, Liability, Increase (Decrease) from Other Change		511	(103)
Separate Account, Liability, Ending Balance		6,481	5,834
Separate Account, Liability, Cash Surrender Value, Amount	[1]	$ 6,101	$ 5,625

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