Future policy benefits (Rollforward) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Liability for Future Policy Benefit, Activity [Line Items]
Deferred profit liability		$ 2,904	$ 1,908
Net liability for future policy benefits, before reinsurance recoverable		19,273	16,690	$ 18,420
Reinsurance recoverable on policy benefits	[1]	295		$ 286
Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		18,407	17,679
Beginning balance at original discount rate		18,518	17,745
Effect of changes in cash flow assumptions		0	(9)
Effect of actual variances from expected experience		(128)	(63)
Adjusted beginning of period balance		18,390	17,673
Issuances		1,408	1,160
Interest accrual		192	181
Net premiums collected (1)	[2]	(1,139)	(801)
Other (including foreign exchange)		132	(109)
Ending balance at original discount rate		18,983	18,104
Effect of changes in discount rate assumptions		(449)	29
Balance – end of period		18,534	18,133
Balance – beginning of period		32,775	30,635
Beginning balance at original discount rate		32,551	30,142
Effect of changes in cash flow assumptions		0	(8)
Effect of actual variances from expected experience		(126)	(61)
Adjusted beginning of period balance		32,425	30,073
Issuances		1,408	1,160
Interest accrual		311	280
Benefits payments		(572)	(556)
Other (including foreign exchange)		215	(162)
Ending balance at original discount rate		33,787	30,795
Effect of changes in discount rate assumptions		(498)	689
Balance – end of period		33,289	31,484
Net liability for future policy benefits		14,755	13,351
Deferred profit liability		2,904	1,908
Net liability for future policy benefits, before reinsurance recoverable		17,659	15,259
Reinsurance recoverable on policy benefits		284	267
Net liability for future policy benefits, after reinsurance recoverable		$ 17,375	$ 14,992
Weighted average duration (years)		21 years 4 months 24 days	21 years 9 months 18 days
Other Segments
Liability for Future Policy Benefit, Activity [Line Items]
Net liability for future policy benefits, before reinsurance recoverable		$ 1,614	$ 1,431
Term Life Insurance | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		1,544	1,523
Beginning balance at original discount rate		1,814	1,819
Effect of changes in cash flow assumptions		0	0
Effect of actual variances from expected experience		2	7
Adjusted beginning of period balance		1,816	1,826
Issuances		70	65
Interest accrual		15	14
Net premiums collected (1)	[2]	(62)	(59)
Other (including foreign exchange)		10	(6)
Ending balance at original discount rate		1,849	1,840
Effect of changes in discount rate assumptions		(282)	(295)
Balance – end of period		1,567	1,545
Balance – beginning of period		2,313	2,238
Beginning balance at original discount rate		2,715	2,647
Effect of changes in cash flow assumptions		0	0
Effect of actual variances from expected experience		9	10
Adjusted beginning of period balance		2,724	2,657
Issuances		70	65
Interest accrual		21	19
Benefits payments		(56)	(51)
Other (including foreign exchange)		8	(6)
Ending balance at original discount rate		2,767	2,684
Effect of changes in discount rate assumptions		(436)	(416)
Balance – end of period		2,331	2,268
Net liability for future policy benefits		764	723
Deferred profit liability		323	291
Net liability for future policy benefits, before reinsurance recoverable		1,087	1,014
Reinsurance recoverable on policy benefits		110	108
Net liability for future policy benefits, after reinsurance recoverable		$ 977	$ 906
Weighted average duration (years)		11 years 1 month 6 days	10 years 6 months
Whole Life Insurance | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		$ 4,749	$ 4,405
Beginning balance at original discount rate		4,616	4,303
Effect of changes in cash flow assumptions		0	(4)
Effect of actual variances from expected experience		53	23
Adjusted beginning of period balance		4,669	4,322
Issuances		495	288
Interest accrual		36	32
Net premiums collected (1)	[2]	(565)	(311)
Other (including foreign exchange)		27	(19)
Ending balance at original discount rate		4,662	4,312
Effect of changes in discount rate assumptions		81	111
Balance – end of period		4,743	4,423
Balance – beginning of period		13,791	12,057
Beginning balance at original discount rate		13,133	11,242
Effect of changes in cash flow assumptions		0	(10)
Effect of actual variances from expected experience		55	24
Adjusted beginning of period balance		13,188	11,256
Issuances		495	288
Interest accrual		112	90
Benefits payments		(87)	(78)
Other (including foreign exchange)		123	(32)
Ending balance at original discount rate		13,831	11,524
Effect of changes in discount rate assumptions		336	905
Balance – end of period		14,167	12,429
Net liability for future policy benefits		9,424	8,006
Deferred profit liability		2,210	1,351
Net liability for future policy benefits, before reinsurance recoverable		11,634	9,357
Reinsurance recoverable on policy benefits		48	45
Net liability for future policy benefits, after reinsurance recoverable		$ 11,586	$ 9,312
Weighted average duration (years)		25 years 9 months 18 days	27 years 10 months 24 days
Accident and Health Insurance Product Line [Member] | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		$ 11,688	$ 11,626
Beginning balance at original discount rate		11,665	11,499
Effect of changes in cash flow assumptions		0	(5)
Effect of actual variances from expected experience		(187)	(93)
Adjusted beginning of period balance		11,478	11,401
Issuances		609	599
Interest accrual		138	133
Net premiums collected (1)	[2]	(390)	(370)
Other (including foreign exchange)		87	(86)
Ending balance at original discount rate		11,922	11,677
Effect of changes in discount rate assumptions		(250)	212
Balance – end of period		11,672	11,889
Balance – beginning of period		15,587	15,693
Beginning balance at original discount rate		15,645	15,652
Effect of changes in cash flow assumptions		0	2
Effect of actual variances from expected experience		(194)	(95)
Adjusted beginning of period balance		15,451	15,559
Issuances		609	599
Interest accrual		170	165
Benefits payments		(422)	(421)
Other (including foreign exchange)		63	(127)
Ending balance at original discount rate		15,871	15,775
Effect of changes in discount rate assumptions		(400)	155
Balance – end of period		15,471	15,930
Net liability for future policy benefits		3,799	4,041
Deferred profit liability		243	202
Net liability for future policy benefits, before reinsurance recoverable		4,042	4,243
Reinsurance recoverable on policy benefits		125	114
Net liability for future policy benefits, after reinsurance recoverable		$ 3,917	$ 4,129
Weighted average duration (years)		10 years	9 years 10 months 24 days
Insurance, Other | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		$ 426	$ 125
Beginning balance at original discount rate		423	124
Effect of changes in cash flow assumptions		0	0
Effect of actual variances from expected experience		4	0
Adjusted beginning of period balance		427	124
Issuances		234	208
Interest accrual		3	2
Net premiums collected (1)	[2]	(122)	(61)
Other (including foreign exchange)		8	2
Ending balance at original discount rate		550	275
Effect of changes in discount rate assumptions		2	1
Balance – end of period		552	276
Balance – beginning of period		1,084	647
Beginning balance at original discount rate		1,058	601
Effect of changes in cash flow assumptions		0	0
Effect of actual variances from expected experience		4	0
Adjusted beginning of period balance		1,062	601
Issuances		234	208
Interest accrual		8	6
Benefits payments		(7)	(6)
Other (including foreign exchange)		21	3
Ending balance at original discount rate		1,318	812
Effect of changes in discount rate assumptions		2	45
Balance – end of period		1,320	857
Net liability for future policy benefits		768	581
Deferred profit liability		128	64
Net liability for future policy benefits, before reinsurance recoverable		896	645
Reinsurance recoverable on policy benefits		1	0
Net liability for future policy benefits, after reinsurance recoverable		$ 895	$ 645
Weighted average duration (years)		27 years 2 months 12 days	23 years 6 months

[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.