Future policy benefits (Rollforward) (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Liability for Future Policy Benefit, Activity [Line Items]
Deferred profit liability		$ 2,132	$ 1,452
Net liability for future policy benefits, before reinsurance recoverable		18,018	14,663	$ 16,121
Reinsurance recoverable on policy benefits	[1]	297		$ 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		9	187
Effect of actual variances from expected experience		(152)	(121)
Adjusted beginning of period balance		17,602	16,759
Issuances		2,253	1,966
Interest accrual		356	322
Net premiums collected (1)	[2]	(1,713)	(1,474)
Other (including foreign exchange)		656	(365)
Ending balance at original discount rate		19,154	17,208
Effect of changes in discount rate assumptions		33	(542)
Balance – end of period		19,187	16,666
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		12	195
Effect of actual variances from expected experience		(150)	(107)
Adjusted beginning of period balance		30,004	28,391
Issuances		2,253	1,966
Interest accrual		558	494
Benefits payments		(1,138)	(1,093)
Other (including foreign exchange)		1,005	(519)
Ending balance at original discount rate		32,682	29,239
Effect of changes in discount rate assumptions		842	(703)
Balance – end of period		33,524	28,536
Net liability for future policy benefits		14,337	11,870
Deferred profit liability		2,132	1,452
Net liability for future policy benefits, before reinsurance recoverable		16,469	13,322
Reinsurance recoverable on policy benefits		275	257
Net liability for future policy benefits, after reinsurance recoverable		$ 16,194	$ 13,065
Weighted average duration (years)		22 years	19 years 1 month 6 days
Other Segments
Liability for Future Policy Benefit, Activity [Line Items]
Net liability for future policy benefits, before reinsurance recoverable		$ 1,549	$ 1,341
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		0	6
Effect of actual variances from expected experience		(4)	(12)
Adjusted beginning of period balance		1,815	1,986
Issuances		116	111
Interest accrual		26	26
Net premiums collected (1)	[2]	(122)	(122)
Other (including foreign exchange)		59	(25)
Ending balance at original discount rate		1,894	1,976
Effect of changes in discount rate assumptions		(296)	(397)
Balance – end of period		1,598	1,579
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		0	8
Effect of actual variances from expected experience		(1)	(9)
Adjusted beginning of period balance		2,646	2,748
Issuances		116	111
Interest accrual		36	35
Benefits payments		(110)	(115)
Other (including foreign exchange)		88	(3)
Ending balance at original discount rate		2,776	2,776
Effect of changes in discount rate assumptions		(432)	(512)
Balance – end of period		2,344	2,264
Net liability for future policy benefits		746	685
Deferred profit liability		306	268
Net liability for future policy benefits, before reinsurance recoverable		1,052	953
Reinsurance recoverable on policy benefits		107	103
Net liability for future policy benefits, after reinsurance recoverable		$ 945	$ 850
Weighted average duration (years)		10 years 4 months 24 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		(4)	70
Effect of actual variances from expected experience		18	21
Adjusted beginning of period balance		4,317	4,036
Issuances		719	620
Interest accrual		65	55
Net premiums collected (1)	[2]	(743)	(603)
Other (including foreign exchange)		134	(77)
Ending balance at original discount rate		4,492	4,031
Effect of changes in discount rate assumptions		142	17
Balance – end of period		4,634	4,048
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		(9)	85
Effect of actual variances from expected experience		18	31
Adjusted beginning of period balance		11,251	10,107
Issuances		719	620
Interest accrual		185	151
Benefits payments		(154)	(179)
Other (including foreign exchange)		300	(169)
Ending balance at original discount rate		12,301	10,530
Effect of changes in discount rate assumptions		1,106	129
Balance – end of period		13,407	10,659
Net liability for future policy benefits		8,773	6,611
Deferred profit liability		1,539	986
Net liability for future policy benefits, before reinsurance recoverable		10,312	7,597
Reinsurance recoverable on policy benefits		46	44
Net liability for future policy benefits, after reinsurance recoverable		$ 10,266	$ 7,553
Weighted average duration (years)		27 years 7 months 6 days	25 years
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		13	111
Effect of actual variances from expected experience		(168)	(129)
Adjusted beginning of period balance		11,344	10,674
Issuances		1,107	1,196
Interest accrual		260	239
Net premiums collected (1)	[2]	(755)	(729)
Other (including foreign exchange)		459	(273)
Ending balance at original discount rate		12,415	11,107
Effect of changes in discount rate assumptions		184	(162)
Balance – end of period		12,599	10,945
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		21	102
Effect of actual variances from expected experience		(170)	(129)
Adjusted beginning of period balance		15,503	15,044
Issuances		1,107	1,196
Interest accrual		325	300
Benefits payments		(864)	(789)
Other (including foreign exchange)		601	(356)
Ending balance at original discount rate		16,672	15,395
Effect of changes in discount rate assumptions		109	(337)
Balance – end of period		16,781	15,058
Net liability for future policy benefits		4,182	4,113
Deferred profit liability		219	174
Net liability for future policy benefits, before reinsurance recoverable		4,401	4,287
Reinsurance recoverable on policy benefits		121	110
Net liability for future policy benefits, after reinsurance recoverable		$ 4,280	$ 4,177
Weighted average duration (years)		10 years	10 years
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		0	0
Effect of actual variances from expected experience		2	(1)
Adjusted beginning of period balance		126	63
Issuances		311	39
Interest accrual		5	2
Net premiums collected (1)	[2]	(93)	(20)
Other (including foreign exchange)		4	10
Ending balance at original discount rate		353	94
Effect of changes in discount rate assumptions		3	0
Balance – end of period		356	94
Balance – beginning of period		647	495
Beginning balance at original discount rate		601	492
Effect of changes in cash flow assumptions		0	0
Effect of actual variances from expected experience		3	0
Adjusted beginning of period balance		604	492
Issuances		311	39
Interest accrual		12	8
Benefits payments		(10)	(10)
Other (including foreign exchange)		16	9
Ending balance at original discount rate		933	538
Effect of changes in discount rate assumptions		59	17
Balance – end of period		992	555
Net liability for future policy benefits		636	461
Deferred profit liability		68	24
Net liability for future policy benefits, before reinsurance recoverable		704	485
Reinsurance recoverable on policy benefits		1	0
Net liability for future policy benefits, after reinsurance recoverable		$ 703	$ 485
Weighted average duration (years)		25 years 3 months 18 days	16 years 3 months 18 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.