Future policy benefits (Rollforward) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2024	Dec. 31, 2023	Jul. 01, 2023
Liability for Future Policy Benefit, Activity [Line Items]
Deferred profit liability		$ 1,724	$ 1,253
Net liability for future policy benefits, before reinsurance recoverable		16,121	13,888
Reinsurance recoverable on policy benefits		289	280
Huatai Group [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Net liability for future policy benefits, before reinsurance recoverable				$ 2,351
Reinsurance recoverable on policy benefits				$ 27
Life Insurance [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		450	(756)
Effect of actual variances from expected experience		(130)	(5)
Adjusted beginning of period balance		17,013	14,768
Consolidation of Huatai Group			1,850
Issuances		3,680	2,170
Interest accrual		731	691
Net premiums collected (1)	[1]	(2,851)	(2,320)
Other (including foreign exchange)		(828)	(466)
Ending balance at original discount rate		17,745	16,693
Effect of changes in discount rate assumptions		(66)	(657)
Balance – end of period		17,679	16,036
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		432	(795)
Effect of actual variances from expected experience		(110)	15
Adjusted beginning of period balance		28,625	23,676
Consolidation of Huatai Group			4,072
Issuances		3,680	2,170
Interest accrual		1,092	1,023
Benefits payments		(2,176)	(2,135)
Other (including foreign exchange)		(1,079)	(503)
Ending balance at original discount rate		30,142	28,303
Effect of changes in discount rate assumptions		493	(841)
Balance – end of period		30,635	27,462
Net liability for future policy benefits		12,956	11,426
Deferred profit liability		1,724	1,253
Net liability for future policy benefits, before reinsurance recoverable		14,680	12,679
Reinsurance recoverable on policy benefits		269	233
Net liability for future policy benefits, after reinsurance recoverable		$ 14,411	$ 12,446
Weighted-average duration (years)		21 years 3 months 18 days	19 years 4 months 24 days
Other Segments [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Net liability for future policy benefits	[2]	$ 1,441	$ 1,209
Term Life Insurance | Life Insurance [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		(141)	22
Effect of actual variances from expected experience		11	(9)
Adjusted beginning of period balance		1,862	1,880
Consolidation of Huatai Group			3
Issuances		221	190
Interest accrual		58	71
Net premiums collected (1)	[1]	(242)	(255)
Other (including foreign exchange)		(80)	103
Ending balance at original discount rate		1,819	1,992
Effect of changes in discount rate assumptions		(296)	(402)
Balance – end of period		1,523	1,590
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		(141)	15
Effect of actual variances from expected experience		20	(4)
Adjusted beginning of period balance		2,628	2,458
Consolidation of Huatai Group			17
Issuances		221	190
Interest accrual		76	90
Benefits payments		(224)	(238)
Other (including foreign exchange)		(54)	232
Ending balance at original discount rate		2,647	2,749
Effect of changes in discount rate assumptions		(409)	(495)
Balance – end of period		2,238	2,254
Net liability for future policy benefits		715	664
Deferred profit liability		279	267
Net liability for future policy benefits, before reinsurance recoverable		994	931
Reinsurance recoverable on policy benefits		108	82
Net liability for future policy benefits, after reinsurance recoverable		$ 886	$ 849
Weighted-average duration (years)		10 years 4 months 24 days	10 years 6 months
Whole Life Insurance | Life Insurance [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		178	40
Effect of actual variances from expected experience		(2)	88
Adjusted beginning of period balance		4,121	2,489
Consolidation of Huatai Group			1,690
Issuances		1,211	318
Interest accrual		128	87
Net premiums collected (1)	[1]	(1,086)	(585)
Other (including foreign exchange)		(71)	(54)
Ending balance at original discount rate		4,303	3,945
Effect of changes in discount rate assumptions		102	5
Balance – end of period		4,405	3,950
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		205	44
Effect of actual variances from expected experience		11	98
Adjusted beginning of period balance		10,207	6,016
Consolidation of Huatai Group			3,659
Issuances		1,211	318
Interest accrual		331	252
Benefits payments		(340)	(333)
Other (including foreign exchange)		(167)	79
Ending balance at original discount rate		11,242	9,991
Effect of changes in discount rate assumptions		815	72
Balance – end of period		12,057	10,063
Net liability for future policy benefits		7,652	6,113
Deferred profit liability		1,210	804
Net liability for future policy benefits, before reinsurance recoverable		8,862	6,917
Reinsurance recoverable on policy benefits		47	45
Net liability for future policy benefits, after reinsurance recoverable		$ 8,815	$ 6,872
Weighted-average duration (years)		27 years 9 months 18 days	25 years 9 months 18 days
Accident and Health [Member] | Life Insurance [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		417	(820)
Effect of actual variances from expected experience		(139)	(84)
Adjusted beginning of period balance		10,970	10,354
Consolidation of Huatai Group			145
Issuances		2,162	1,653
Interest accrual		540	531
Net premiums collected (1)	[1]	(1,483)	(1,457)
Other (including foreign exchange)		(690)	(534)
Ending balance at original discount rate		11,499	10,692
Effect of changes in discount rate assumptions		127	(260)
Balance – end of period		11,626	10,432
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		373	(858)
Effect of actual variances from expected experience		(141)	(78)
Adjusted beginning of period balance		15,303	14,919
Consolidation of Huatai Group			163
Issuances		2,162	1,653
Interest accrual		668	672
Benefits payments		(1,594)	(1,551)
Other (including foreign exchange)		(887)	(785)
Ending balance at original discount rate		15,652	15,071
Effect of changes in discount rate assumptions		41	(421)
Balance – end of period		15,693	14,650
Net liability for future policy benefits		4,067	4,218
Deferred profit liability		196	165
Net liability for future policy benefits, before reinsurance recoverable		4,263	4,383
Reinsurance recoverable on policy benefits		113	106
Net liability for future policy benefits, after reinsurance recoverable		$ 4,150	$ 4,277
Weighted-average duration (years)		9 years 9 months 18 days	10 years 4 months 24 days
Insurance, Other [Member] | Life Insurance [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		(4)	2
Effect of actual variances from expected experience		0	0
Adjusted beginning of period balance		60	45
Consolidation of Huatai Group			12
Issuances		86	9
Interest accrual		5	2
Net premiums collected (1)	[1]	(40)	(23)
Other (including foreign exchange)		13	19
Ending balance at original discount rate		124	64
Effect of changes in discount rate assumptions		1	0
Balance – end of period		125	64
Balance – beginning of period		495	269
Beginning balance at original discount rate		492	280
Effect of changes in cash flow assumptions		(5)	4
Effect of actual variances from expected experience		0	(1)
Adjusted beginning of period balance		487	283
Consolidation of Huatai Group			233
Issuances		86	9
Interest accrual		17	9
Benefits payments		(18)	(13)
Other (including foreign exchange)		29	(29)
Ending balance at original discount rate		601	492
Effect of changes in discount rate assumptions		46	3
Balance – end of period		647	495
Net liability for future policy benefits		522	431
Deferred profit liability		39	17
Net liability for future policy benefits, before reinsurance recoverable		561	448
Reinsurance recoverable on policy benefits		1	0
Net liability for future policy benefits, after reinsurance recoverable		$ 560	$ 448
Weighted-average duration (years)		18 years 7 months 6 days	15 years

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

[2] Other business principally comprises certain Overseas General Insurance accident and health (A&H) policies and certain Chubb Life Re business.