Policyholders' account balances (Policyholder Account Balance Rollforward) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Policyholder Account Balance [Line Items]
Balance – beginning of period		$ 6,880	$ 2,593	$ 6,789	$ 2,573
Policyholder Account Balance, Premium Received		334	68
Policyholder Account Balance, Policy Charge	[1]	(36)	(34)
Policyholder Account Balance, Surrender and Withdrawal		(119)	(23)
Policyholder Account Balance, Benefit Payment	[2]	(116)	(10)
Policyholder Account Balance, Interest Expense		43	16
Policyholder Account Balance, Increase (Decrease) from Other Change		(15)	(3)
Balance - end of period		6,880	2,593	6,789	2,573
Balance – beginning of period		680	585	673	567
Policyholder Account Balance, Ending Balance		7,560	3,178
Universal Life
Policyholder Account Balance [Line Items]
Balance – beginning of period		1,840	1,208	1,876	1,199
Policyholder Account Balance, Premium Received		72	50
Policyholder Account Balance, Policy Charge	[1]	(34)	(30)
Policyholder Account Balance, Surrender and Withdrawal		(32)	(15)
Policyholder Account Balance, Benefit Payment	[2]	(54)	(4)
Policyholder Account Balance, Interest Expense		13	8
Policyholder Account Balance, Increase (Decrease) from Other Change		(1)	0
Balance - end of period		1,840	1,208	1,876	1,199
Policyholder Account Balance, Ending Balance		$ 1,840	$ 1,208
Policyholder Account Balance, Weighted Average Crediting Rate		2.90%	2.60%
Policyholder Account Balance, Net Amount at Risk	[3]	$ 12,014	$ 11,394
Policyholder Account Balance, Cash Surrender Value		1,623	1,005
Annuities [Member]
Policyholder Account Balance [Line Items]
Balance – beginning of period	[4]	2,484		2,411
Policyholder Account Balance, Premium Received	[4]	131
Policyholder Account Balance, Policy Charge	[1],[4]	0
Policyholder Account Balance, Surrender and Withdrawal	[4]	(10)
Policyholder Account Balance, Benefit Payment	[2],[4]	(59)
Policyholder Account Balance, Interest Expense	[4]	16
Policyholder Account Balance, Increase (Decrease) from Other Change	[4]	(5)
Balance - end of period	[4]	2,484		2,411
Policyholder Account Balance, Ending Balance		$ 2,484
Policyholder Account Balance, Weighted Average Crediting Rate		2.60%
Policyholder Account Balance, Net Amount at Risk	[3]	$ 0
Policyholder Account Balance, Cash Surrender Value		1,605
Insurance, Other
Policyholder Account Balance [Line Items]
Balance – beginning of period	[5]	2,556	1,385	2,502	1,374
Policyholder Account Balance, Premium Received	[5]	131	18
Policyholder Account Balance, Policy Charge	[1],[5]	(2)	(4)
Policyholder Account Balance, Surrender and Withdrawal	[5]	(77)	(8)
Policyholder Account Balance, Benefit Payment	[2],[5]	(3)	(6)
Policyholder Account Balance, Interest Expense	[5]	14	8
Policyholder Account Balance, Increase (Decrease) from Other Change	[5]	(9)	(3)
Balance - end of period	[5]	2,556	1,385	$ 2,502	$ 1,374
Policyholder Account Balance, Ending Balance		$ 2,556	$ 1,385
Policyholder Account Balance, Weighted Average Crediting Rate		2.50%	3.00%
Policyholder Account Balance, Net Amount at Risk	[3]	$ 499	$ 156
Policyholder Account Balance, Cash Surrender Value		$ 2,239	$ 1,075

[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] Includes benefit payments upon maturity as well as death benefits.

[3] 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.

[4] Relates to Huatai Life.

[5] Other primarily comprises policyholder account balances related to investment linked products including endowment and investment contracts, none of which bear significant insurance risk.