Future policy benefits (Rollforward) (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Liability for Future Policy Benefit, Activity [Line Items]
Deferred profit liability		$ 2,353	$ 1,622
Net liability for future policy benefits, before reinsurance recoverable		18,288	16,003	$ 16,121
Reinsurance recoverable on policy benefits	[1]	302		$ 289
Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		17,679	16,036
Beginning balance at original discount rate		17,745	16,693
Effect of changes in cash flow assumptions		(503)	410
Effect of actual variances from expected experience		(196)	(112)
Adjusted beginning of period balance		17,046	16,991
Issuances		3,356	2,873
Interest accrual		571	563
Net premiums collected (1)	[2]	(2,640)	(2,167)
Other (including foreign exchange)		554	(140)
Ending balance at original discount rate		18,887	18,120
Effect of changes in discount rate assumptions		69	(56)
Balance – end of period		18,956	18,064
Balance – beginning of period		30,635	27,462
Beginning balance at original discount rate		30,142	28,303
Effect of changes in cash flow assumptions		(568)	387
Effect of actual variances from expected experience		(192)	(93)
Adjusted beginning of period balance		29,382	28,597
Issuances		3,356	2,873
Interest accrual		880	829
Benefits payments		(1,758)	(1,633)
Other (including foreign exchange)		923	(65)
Ending balance at original discount rate		32,783	30,601
Effect of changes in discount rate assumptions		572	455
Balance – end of period		33,355	31,056
Net liability for future policy benefits		14,399	12,992
Deferred profit liability		2,353	1,622
Net liability for future policy benefits, before reinsurance recoverable		16,752	14,614
Reinsurance recoverable on policy benefits		273	266
Net liability for future policy benefits, after reinsurance recoverable		$ 16,479	$ 14,348
Weighted average duration (years)		21 years 8 months 12 days	21 years 1 month 6 days
Other Segments
Liability for Future Policy Benefit, Activity [Line Items]
Net liability for future policy benefits, before reinsurance recoverable		$ 1,536	$ 1,389
Term Life Insurance | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		1,523	1,590
Beginning balance at original discount rate		1,819	1,992
Effect of changes in cash flow assumptions		(56)	(140)
Effect of actual variances from expected experience		5	6
Adjusted beginning of period balance		1,768	1,858
Issuances		166	161
Interest accrual		43	45
Net premiums collected (1)	[2]	(188)	(183)
Other (including foreign exchange)		47	(10)
Ending balance at original discount rate		1,836	1,871
Effect of changes in discount rate assumptions		(253)	(287)
Balance – end of period		1,583	1,584
Balance – beginning of period		2,238	2,254
Beginning balance at original discount rate		2,647	2,749
Effect of changes in cash flow assumptions		(54)	(137)
Effect of actual variances from expected experience		9	13
Adjusted beginning of period balance		2,602	2,625
Issuances		166	161
Interest accrual		58	59
Benefits payments		(170)	(173)
Other (including foreign exchange)		74	27
Ending balance at original discount rate		2,730	2,699
Effect of changes in discount rate assumptions		(385)	(390)
Balance – end of period		2,345	2,309
Net liability for future policy benefits		762	725
Deferred profit liability		309	276
Net liability for future policy benefits, before reinsurance recoverable		1,071	1,001
Reinsurance recoverable on policy benefits		101	109
Net liability for future policy benefits, after reinsurance recoverable		$ 970	$ 892
Weighted average duration (years)		10 years 8 months 12 days	10 years 2 months 12 days
Whole Life Insurance | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		$ 4,405	$ 3,950
Beginning balance at original discount rate		4,303	3,945
Effect of changes in cash flow assumptions		(65)	160
Effect of actual variances from expected experience		13	9
Adjusted beginning of period balance		4,251	4,114
Issuances		1,280	942
Interest accrual		107	91
Net premiums collected (1)	[2]	(1,192)	(852)
Other (including foreign exchange)		170	14
Ending balance at original discount rate		4,616	4,309
Effect of changes in discount rate assumptions		154	94
Balance – end of period		4,770	4,403
Balance – beginning of period		12,057	10,063
Beginning balance at original discount rate		11,242	9,991
Effect of changes in cash flow assumptions		(93)	181
Effect of actual variances from expected experience		11	21
Adjusted beginning of period balance		11,160	10,193
Issuances		1,280	942
Interest accrual		291	240
Benefits payments		(243)	(260)
Other (including foreign exchange)		394	55
Ending balance at original discount rate		12,882	11,170
Effect of changes in discount rate assumptions		820	739
Balance – end of period		13,702	11,909
Net liability for future policy benefits		8,932	7,506
Deferred profit liability		1,744	1,120
Net liability for future policy benefits, before reinsurance recoverable		10,676	8,626
Reinsurance recoverable on policy benefits		48	45
Net liability for future policy benefits, after reinsurance recoverable		$ 10,628	$ 8,581
Weighted average duration (years)		27 years	27 years 9 months 18 days
Accident and Health Insurance Product Line [Member] | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		$ 11,626	$ 10,432
Beginning balance at original discount rate		11,499	10,692
Effect of changes in cash flow assumptions		(389)	394
Effect of actual variances from expected experience		(213)	(126)
Adjusted beginning of period balance		10,897	10,960
Issuances		1,542	1,717
Interest accrual		413	424
Net premiums collected (1)	[2]	(1,145)	(1,105)
Other (including foreign exchange)		330	(158)
Ending balance at original discount rate		12,037	11,838
Effect of changes in discount rate assumptions		164	136
Balance – end of period		12,201	11,974
Balance – beginning of period		15,693	14,650
Beginning balance at original discount rate		15,652	15,071
Effect of changes in cash flow assumptions		(434)	348
Effect of actual variances from expected experience		(212)	(127)
Adjusted beginning of period balance		15,006	15,292
Issuances		1,542	1,717
Interest accrual		511	519
Benefits payments		(1,331)	(1,186)
Other (including foreign exchange)		430	(188)
Ending balance at original discount rate		16,158	16,154
Effect of changes in discount rate assumptions		101	65
Balance – end of period		16,259	16,219
Net liability for future policy benefits		4,058	4,245
Deferred profit liability		231	194
Net liability for future policy benefits, before reinsurance recoverable		4,289	4,439
Reinsurance recoverable on policy benefits		123	112
Net liability for future policy benefits, after reinsurance recoverable		$ 4,166	$ 4,327
Weighted average duration (years)		10 years	9 years 9 months 18 days
Insurance, Other | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		$ 125	$ 64
Beginning balance at original discount rate		124	64
Effect of changes in cash flow assumptions		7	(4)
Effect of actual variances from expected experience		(1)	(1)
Adjusted beginning of period balance		130	59
Issuances		368	53
Interest accrual		8	3
Net premiums collected (1)	[2]	(115)	(27)
Other (including foreign exchange)		7	14
Ending balance at original discount rate		398	102
Effect of changes in discount rate assumptions		4	1
Balance – end of period		402	103
Balance – beginning of period		647	495
Beginning balance at original discount rate		601	492
Effect of changes in cash flow assumptions		13	(5)
Effect of actual variances from expected experience		0	0
Adjusted beginning of period balance		614	487
Issuances		368	53
Interest accrual		20	11
Benefits payments		(14)	(14)
Other (including foreign exchange)		25	41
Ending balance at original discount rate		1,013	578
Effect of changes in discount rate assumptions		36	41
Balance – end of period		1,049	619
Net liability for future policy benefits		647	516
Deferred profit liability		69	32
Net liability for future policy benefits, before reinsurance recoverable		716	548
Reinsurance recoverable on policy benefits		1	0
Net liability for future policy benefits, after reinsurance recoverable		$ 715	$ 548
Weighted average duration (years)		25 years 8 months 12 days	17 years 7 months 6 days

[1] Net of valuation allowance for uncollectible reinsurance.

[2] Net premiums collected represent the portion of gross premiums collected from policyholders that is used to fund expected benefit.