Policyholders' account balances (Policyholder Account Balance Rollforward) (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2023	Jun. 30, 2022
Policyholder Account Balance [Line Items]
Policyholder Account Balance, Beginning Balance		$ 3,140	$ 2,766
Policyholder Account Balance, Premium Received		228	253
Policyholder Account Balance, Policy Charge	[1]	(94)	(97)
Policyholder Account Balance, Surrender and Withdrawal		(76)	(72)
Policyholder Account Balance, Benefit Payment		(26)	(14)
Policyholder Account Balance, Interest Expense		37	38
Policyholder Account Balance, Increase (Decrease) from Other Change		6	125
Policyholder Account Balance, Ending Balance		3,215	2,749
Universal Life
Policyholder Account Balance [Line Items]
Policyholder Account Balance, Beginning Balance		1,719	1,612
Policyholder Account Balance, Premium Received		175	195
Policyholder Account Balance, Policy Charge	[1]	(89)	(92)
Policyholder Account Balance, Surrender and Withdrawal		(41)	(37)
Policyholder Account Balance, Benefit Payment		(4)	(3)
Policyholder Account Balance, Interest Expense		22	20
Policyholder Account Balance, Increase (Decrease) from Other Change		19	36
Policyholder Account Balance, Ending Balance		$ 1,801	$ 1,659
Policyholder Account Balance, Weighted Average Crediting Rate		3.80%	3.50%
Policyholder Account Balance, Net Amount at Risk	[2]	$ 10,405	$ 10,041
Policyholder Account Balance, Cash Surrender Value		978	876
Insurance, Other
Policyholder Account Balance [Line Items]
Policyholder Account Balance, Beginning Balance		1,421	1,154
Policyholder Account Balance, Premium Received		53	58
Policyholder Account Balance, Policy Charge	[1]	(5)	(5)
Policyholder Account Balance, Surrender and Withdrawal		(35)	(35)
Policyholder Account Balance, Benefit Payment		(22)	(11)
Policyholder Account Balance, Interest Expense		15	18
Policyholder Account Balance, Increase (Decrease) from Other Change		(13)	89
Policyholder Account Balance, Ending Balance		$ 1,414	$ 1,090
Policyholder Account Balance, Weighted Average Crediting Rate		2.20%	3.10%
Policyholder Account Balance, Net Amount at Risk	[2]	$ 1,447	$ 507
Policyholder Account Balance, Cash Surrender Value		$ 1,122	$ 831

[1] Contracts included in the policyholder account balances are generally charged a premium and/or monthly assessments on the basis of the account balance

[2] For those guarantees of benefits that are payable in the event of death, the net amount at risk is defined as the current guaranteed minimum death benefit in excess of the current account balance at the balance sheet date.