Policyholders' account balances (Policyholder Account Balance Rollforward) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Policyholder Account Balance [Line Items]
Policyholder Account Balance, Beginning Balance		$ 3,140	$ 2,766
Policyholder Account Balance, Premium Received		110	123
Policyholder Account Balance, Policy Charge	[1]	(48)	(48)
Policyholder Account Balance, Surrender and Withdrawal		(31)	(31)
Policyholder Account Balance, Benefit Payment		(11)	(7)
Policyholder Account Balance, Interest Expense		16	17
Policyholder Account Balance, Increase (Decrease) from Other Change		2	52
Policyholder Account Balance, Ending Balance		3,178	2,768
Universal Life
Policyholder Account Balance [Line Items]
Policyholder Account Balance, Beginning Balance		1,719	1,612
Policyholder Account Balance, Premium Received		85	95
Policyholder Account Balance, Policy Charge	[1]	(45)	(46)
Policyholder Account Balance, Surrender and Withdrawal		(16)	(14)
Policyholder Account Balance, Benefit Payment		(4)	(2)
Policyholder Account Balance, Interest Expense		11	11
Policyholder Account Balance, Increase (Decrease) from Other Change		(4)	6
Policyholder Account Balance, Ending Balance		$ 1,746	$ 1,650
Policyholder Account Balance, Weighted Average Crediting Rate		3.60%	3.60%
Policyholder Account Balance, Net Amount at Risk	[2]	$ 9,934	$ 10,259
Policyholder Account Balance, Cash Surrender Value		937	869
Insurance, Other
Policyholder Account Balance [Line Items]
Policyholder Account Balance, Beginning Balance		1,421	1,154
Policyholder Account Balance, Premium Received		25	28
Policyholder Account Balance, Policy Charge	[1]	(3)	(2)
Policyholder Account Balance, Surrender and Withdrawal		(15)	(17)
Policyholder Account Balance, Benefit Payment		(7)	(5)
Policyholder Account Balance, Interest Expense		5	6
Policyholder Account Balance, Increase (Decrease) from Other Change		6	46
Policyholder Account Balance, Ending Balance		$ 1,432	$ 1,118
Policyholder Account Balance, Weighted Average Crediting Rate		2.60%	3.40%
Policyholder Account Balance, Net Amount at Risk	[2]	$ 1,450	$ 518
Policyholder Account Balance, Cash Surrender Value		$ 1,137	$ 865

[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.