Future policy benefits (Rollforward) (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Liability for Future Policy Benefit, Activity [Line Items]
Deferred profit liability		$ 1,452	$ 1,044
Net liability for future policy benefits, before reinsurance recoverable		14,663	11,064	$ 13,888
Less: Reinsurance recoverable on future policy benefits	[1]	291		280
Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		16,036	14,867
Beginning balance at original discount rate				16,693	$ 15,529
Effect of changes in cash flow assumptions				187	(756)
Effect of actual variances from expected experience				(121)	(45)
Adjusted beginning of period balance		16,759	14,728
Issuances		1,966	729
Interest accrual		322	298
Net premiums collected (1)	[2]	(1,474)	(922)
Other (including foreign exchange)		(365)	(60)
Ending balance at original discount rate		17,208	14,773
Effect of changes in discount rate assumptions		(542)	(421)
Balance – end of period		16,666	14,352
Balance – beginning of period		27,462	23,324
Beginning balance at original discount rate				28,303	24,456
Effect of changes in cash flow assumptions				195	(761)
Effect of actual variances from expected experience				(107)	(36)
Adjusted beginning of period balance		28,391	23,659
Issuances		1,966	729
Interest accrual		494	440
Benefits payments		(1,093)	(927)
Other (including foreign exchange)		(519)	78
Ending balance at original discount rate		29,239	23,979
Effect of changes in discount rate assumptions		(703)	(782)
Balance – end of period		28,536	23,197
Net liability for future policy benefits		11,870	8,845
Deferred profit liability		1,452	1,044
Net liability for future policy benefits, before reinsurance recoverable		13,322	9,889
Less: Reinsurance recoverable on future policy benefits		257	272
Net liability for future policy benefits, after reinsurance recoverable		$ 13,065	$ 9,617
Weighted average duration (years)		19 years 1 month 6 days	17 years 7 months 6 days
Other Segments
Liability for Future Policy Benefit, Activity [Line Items]
Net liability for future policy benefits, before reinsurance recoverable		$ 1,341	$ 1,175
Term Life Insurance | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		1,590	1,806
Beginning balance at original discount rate				1,992	1,867
Effect of changes in cash flow assumptions				6	16
Effect of actual variances from expected experience				(12)	(6)
Adjusted beginning of period balance		1,986	1,877
Issuances		111	63
Interest accrual		26	37
Net premiums collected (1)	[2]	(122)	(87)
Other (including foreign exchange)		(25)	78
Ending balance at original discount rate		1,976	1,968
Effect of changes in discount rate assumptions		(397)	(54)
Balance – end of period		1,579	1,914
Balance – beginning of period		2,254	2,321
Beginning balance at original discount rate				2,749	2,447
Effect of changes in cash flow assumptions				8	19
Effect of actual variances from expected experience				(9)	(6)
Adjusted beginning of period balance		2,748	2,460
Issuances		111	63
Interest accrual		35	43
Benefits payments		(115)	(85)
Other (including foreign exchange)		(3)	184
Ending balance at original discount rate		2,776	2,665
Effect of changes in discount rate assumptions		(512)	(127)
Balance – end of period		2,264	2,538
Net liability for future policy benefits		685	624
Deferred profit liability		268	243
Net liability for future policy benefits, before reinsurance recoverable		953	867
Less: Reinsurance recoverable on future policy benefits		103	110
Net liability for future policy benefits, after reinsurance recoverable		$ 850	$ 757
Weighted average duration (years)		10 years 2 months 12 days	9 years 4 months 24 days
Whole Life Insurance | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		$ 3,950	$ 2,308
Beginning balance at original discount rate				3,945	2,361
Effect of changes in cash flow assumptions				70	(1)
Effect of actual variances from expected experience				21	41
Adjusted beginning of period balance		4,036	2,401
Issuances		620	123
Interest accrual		55	34
Net premiums collected (1)	[2]	(603)	(170)
Other (including foreign exchange)		(77)	11
Ending balance at original discount rate		4,031	2,399
Effect of changes in discount rate assumptions		17	(21)
Balance – end of period		4,048	2,378
Balance – beginning of period		10,063	5,696
Beginning balance at original discount rate				9,991	5,874
Effect of changes in cash flow assumptions				85	(1)
Effect of actual variances from expected experience				31	46
Adjusted beginning of period balance		10,107	5,919
Issuances		620	123
Interest accrual		151	105
Benefits payments		(179)	(130)
Other (including foreign exchange)		(169)	423
Ending balance at original discount rate		10,530	6,440
Effect of changes in discount rate assumptions		129	(76)
Balance – end of period		10,659	6,364
Net liability for future policy benefits		6,611	3,986
Deferred profit liability		986	640
Net liability for future policy benefits, before reinsurance recoverable		7,597	4,626
Less: Reinsurance recoverable on future policy benefits		44	42
Net liability for future policy benefits, after reinsurance recoverable		$ 7,553	$ 4,584
Weighted average duration (years)		25 years	25 years 3 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		$ 10,432	$ 10,711
Beginning balance at original discount rate				10,692	11,258
Effect of changes in cash flow assumptions				111	(772)
Effect of actual variances from expected experience				(129)	(79)
Adjusted beginning of period balance		10,674	10,407
Issuances		1,196	540
Interest accrual		239	226
Net premiums collected (1)	[2]	(729)	(654)
Other (including foreign exchange)		(273)	(150)
Ending balance at original discount rate		11,107	10,369
Effect of changes in discount rate assumptions		(162)	(346)
Balance – end of period		10,945	10,023
Balance – beginning of period		14,650	15,038
Beginning balance at original discount rate				15,071	15,855
Effect of changes in cash flow assumptions				102	(782)
Effect of actual variances from expected experience				(129)	(75)
Adjusted beginning of period balance		15,044	14,998
Issuances		1,196	540
Interest accrual		300	289
Benefits payments		(789)	(707)
Other (including foreign exchange)		(356)	(507)
Ending balance at original discount rate		15,395	14,613
Effect of changes in discount rate assumptions		(337)	(575)
Balance – end of period		15,058	14,038
Net liability for future policy benefits		4,113	4,015
Deferred profit liability		174	148
Net liability for future policy benefits, before reinsurance recoverable		4,287	4,163
Less: Reinsurance recoverable on future policy benefits		110	119
Net liability for future policy benefits, after reinsurance recoverable		$ 4,177	$ 4,044
Weighted average duration (years)		10 years	10 years 6 months
Insurance, Other | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		$ 64	$ 42
Beginning balance at original discount rate				64	43
Effect of changes in cash flow assumptions				0	1
Effect of actual variances from expected experience				(1)	(1)
Adjusted beginning of period balance		63	43
Issuances		39	3
Interest accrual		2	1
Net premiums collected (1)	[2]	(20)	(11)
Other (including foreign exchange)		10	1
Ending balance at original discount rate		94	37
Effect of changes in discount rate assumptions		0	0
Balance – end of period		94	37
Balance – beginning of period		495	269
Beginning balance at original discount rate				492	280
Effect of changes in cash flow assumptions				0	3
Effect of actual variances from expected experience				$ 0	$ (1)
Adjusted beginning of period balance		492	282
Issuances		39	3
Interest accrual		8	3
Benefits payments		(10)	(5)
Other (including foreign exchange)		9	(22)
Ending balance at original discount rate		538	261
Effect of changes in discount rate assumptions		17	(4)
Balance – end of period		555	257
Net liability for future policy benefits		461	220
Deferred profit liability		24	13
Net liability for future policy benefits, before reinsurance recoverable		485	233
Less: Reinsurance recoverable on future policy benefits		0	1
Net liability for future policy benefits, after reinsurance recoverable		$ 485	$ 232
Weighted average duration (years)		16 years 3 months 18 days	14 years

[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.