Policyholders' account balances (Policyholder Account Balance Rollforward) (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Dec. 31, 2023
Policyholder Account Balance [Line Items]
Balance – beginning of period		$ 6,748	$ 6,789
Policyholder Account Balance, Premium Received		706	818
Policyholder Account Balance, Policy Charge	[1]	(88)	(105)
Policyholder Account Balance, Surrender and Withdrawal		(258)	(327)
Policyholder Account Balance, Benefit Payment	[2]	(206)	(215)
Policyholder Account Balance, Interest Expense		130	108
Policyholder Account Balance, Increase (Decrease) from Other Change		169	(200)
Balance – end of period		7,201	6,868
Unearned Revenue Liability		760	712	$ 711	$ 673
Policyholder Account Balance, Other Reconciling Items	[3]	578	556
Policyholder Account Balance, Ending Balance		8,539	8,136
Universal Life
Policyholder Account Balance [Line Items]
Balance – beginning of period		1,809	1,876
Policyholder Account Balance, Premium Received		158	204
Policyholder Account Balance, Policy Charge	[1]	(81)	(98)
Policyholder Account Balance, Surrender and Withdrawal		(91)	(95)
Policyholder Account Balance, Benefit Payment	[2]	(24)	(59)
Policyholder Account Balance, Interest Expense		35	38
Policyholder Account Balance, Increase (Decrease) from Other Change		77	3
Balance – end of period		1,883	1,869
Policyholder Account Balance, Ending Balance		$ 1,883	$ 1,869
Policyholder Account Balance, Weighted Average Crediting Rate	[4]	2.60%	2.70%
Policyholder Account Balance, Net Amount at Risk	[5]	$ 11,474	$ 12,648
Policyholder Account Balance, Cash Surrender Value		1,747	1,699
Annuities [Member]
Policyholder Account Balance [Line Items]
Balance – beginning of period	[6]	2,585	2,411
Policyholder Account Balance, Premium Received	[6]	232	294
Policyholder Account Balance, Policy Charge	[1],[6]	0	0
Policyholder Account Balance, Surrender and Withdrawal	[6]	(24)	(30)
Policyholder Account Balance, Benefit Payment	[2],[6]	(116)	(116)
Policyholder Account Balance, Interest Expense	[6]	36	29
Policyholder Account Balance, Increase (Decrease) from Other Change	[6]	49	20
Balance – end of period	[6]	2,762	2,608
Policyholder Account Balance, Ending Balance		$ 2,762	$ 2,608
Policyholder Account Balance, Weighted Average Crediting Rate	[4]	1.80%	1.60%
Policyholder Account Balance, Net Amount at Risk	[5]	$ 30	$ 0
Policyholder Account Balance, Cash Surrender Value		1,827	1,691
Insurance, Other
Policyholder Account Balance [Line Items]
Balance – beginning of period	[7]	2,354	2,502
Policyholder Account Balance, Premium Received	[7]	316	320
Policyholder Account Balance, Policy Charge	[1],[7]	(7)	(7)
Policyholder Account Balance, Surrender and Withdrawal	[7]	(143)	(202)
Policyholder Account Balance, Benefit Payment	[2],[7]	(66)	(40)
Policyholder Account Balance, Interest Expense	[7]	59	41
Policyholder Account Balance, Increase (Decrease) from Other Change	[7]	43	(223)
Balance – end of period	[7]	2,556	2,391
Policyholder Account Balance, Ending Balance		$ 2,556	$ 2,391
Policyholder Account Balance, Weighted Average Crediting Rate	[4]	3.30%	2.70%
Policyholder Account Balance, Net Amount at Risk	[5]	$ 366	$ 440
Policyholder Account Balance, Cash Surrender Value		$ 2,264	$ 2,091

[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] Primarily comprises unpaid dividends on certain participating policies.

[4] Calculated using actual interest credited for the nine months ended September 30, 2025 and 2024, respectively.

[5] 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.

[6] Relates to Huatai Life.

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