Future policy benefits (Rollforward) (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2021
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		$ 13,024	$ 4,313
Beginning balance at original discount rate				$ 13,685	$ 3,991
Effect of changes in cash flow assumptions				(734)	(32)
Effect of actual variances from expected experience				(127)	(139)
Adjusted beginning of period balance		12,824	3,820
Consolidation of Huatai Group		1,850
Acquisition of Cigna			9,737
Issuances		1,435	601
Interest accrual		529	267
Net premiums collected (1)	[1]	(1,515)	(703)
Other (including foreign exchange)		259	(639)
Ending balance at original discount rate		14,864	13,083
Effect of changes in discount rate assumptions		(629)	(686)
Balance – end of period		14,235	12,397
Balance – beginning of period		21,920	10,775
Beginning balance at original discount rate				23,052	9,402
Effect of changes in cash flow assumptions				(770)	(38)
Effect of actual variances from expected experience				(112)	(144)
Adjusted beginning of period balance		22,170	9,220
Consolidation of Huatai Group		4,137
Acquisition of Cigna			13,583
Issuances		1,436	606
Interest accrual		750	420
Benefits payments		(1,404)	(704)
Other (including foreign exchange)		(336)	1,072
Ending balance at original discount rate		26,753	22,053
Effect of changes in discount rate assumptions		(1,227)	(1,240)
Balance – end of period		25,526	20,813
Net liability for future policy benefits		12,009	9,151
Deferred profit liability		1,100	755
Net liability for future policy benefits, per consolidated balance sheet		13,109	9,906	10,476		$ 7,652
Less: Reinsurance recoverable on future policy benefits		315	312
Net liability for future policy benefits, after reinsurance recoverable		$ 12,794	$ 9,594
Weighted-average duration (years)		18 years 8 months 12 days	16 years 2 months 12 days
Term Life Insurance | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		$ 818	$ 422
Beginning balance at original discount rate				879	397
Effect of changes in cash flow assumptions				35	0
Effect of actual variances from expected experience				(13)	(31)
Adjusted beginning of period balance		901	366
Consolidation of Huatai Group		3
Acquisition of Cigna			445
Issuances		90	95
Interest accrual		45	45
Net premiums collected (1)	[1]	(127)	(93)
Other (including foreign exchange)		9	(46)
Ending balance at original discount rate		903	812
Effect of changes in discount rate assumptions		(69)	(59)
Balance – end of period		834	753
Balance – beginning of period		1,427	921
Beginning balance at original discount rate				1,555	858
Effect of changes in cash flow assumptions				31	(5)
Effect of actual variances from expected experience				(10)	(32)
Adjusted beginning of period balance		1,576	821
Consolidation of Huatai Group		17
Acquisition of Cigna			668
Issuances		90	100
Interest accrual		54	52
Benefits payments		(119)	(82)
Other (including foreign exchange)		92	112
Ending balance at original discount rate		1,710	1,447
Effect of changes in discount rate assumptions		(152)	(126)
Balance – end of period		1,558	1,321
Net liability for future policy benefits		724	568
Deferred profit liability		223	172
Net liability for future policy benefits, per consolidated balance sheet		947	740			454
Less: Reinsurance recoverable on future policy benefits		111	111
Net liability for future policy benefits, after reinsurance recoverable		$ 836	$ 629
Weighted-average duration (years)		10 years 2 months 12 days	9 years
Whole Life Insurance | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		$ 2,301	$ 1,341
Beginning balance at original discount rate				2,354	1,243
Effect of changes in cash flow assumptions				40	(3)
Effect of actual variances from expected experience				6	12
Adjusted beginning of period balance		2,400	1,252
Consolidation of Huatai Group		1,690
Acquisition of Cigna			1,078
Issuances		274	155
Interest accrual		62	37
Net premiums collected (1)	[1]	(375)	(156)
Other (including foreign exchange)		56	(102)
Ending balance at original discount rate		3,995	2,264
Effect of changes in discount rate assumptions		(62)	(95)
Balance – end of period		3,933	2,169
Balance – beginning of period		6,048	4,785
Beginning balance at original discount rate				6,225	3,833
Effect of changes in cash flow assumptions				44	(3)
Effect of actual variances from expected experience				12	14
Adjusted beginning of period balance		6,281	3,844
Consolidation of Huatai Group		3,659
Acquisition of Cigna			2,267
Issuances		276	155
Interest accrual		176	123
Benefits payments		(212)	(151)
Other (including foreign exchange)		22	207
Ending balance at original discount rate		10,202	6,031
Effect of changes in discount rate assumptions		(274)	(308)
Balance – end of period		9,928	5,723
Net liability for future policy benefits		5,995	3,554
Deferred profit liability		707	450
Net liability for future policy benefits, per consolidated balance sheet		6,702	4,004			3,767
Less: Reinsurance recoverable on future policy benefits		47	56
Net liability for future policy benefits, after reinsurance recoverable		$ 6,655	$ 3,948
Weighted-average duration (years)		26 years 6 months	24 years 8 months 12 days
Accident and Health Insurance Product Line [Member] | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		$ 9,863	$ 2,520
Beginning balance at original discount rate				10,409	2,323
Effect of changes in cash flow assumptions				(811)	(29)
Effect of actual variances from expected experience				(120)	(120)
Adjusted beginning of period balance		9,478	2,174
Consolidation of Huatai Group		145
Acquisition of Cigna			8,191
Issuances		1,066	348
Interest accrual		421	184
Net premiums collected (1)	[1]	(998)	(445)
Other (including foreign exchange)		212	(487)
Ending balance at original discount rate		9,900	9,965
Effect of changes in discount rate assumptions		(497)	(531)
Balance – end of period		9,403	9,434
Balance – beginning of period		14,206	4,939
Beginning balance at original discount rate				15,022	4,589
Effect of changes in cash flow assumptions				(848)	(41)
Effect of actual variances from expected experience				(114)	(126)
Adjusted beginning of period balance		14,060	4,422
Consolidation of Huatai Group		163
Acquisition of Cigna			10,542
Issuances		1,065	348
Interest accrual		514	242
Benefits payments		(1,065)	(469)
Other (including foreign exchange)		(628)	651
Ending balance at original discount rate		14,109	14,434
Effect of changes in discount rate assumptions		(790)	(790)
Balance – end of period		13,319	13,644
Net liability for future policy benefits		3,916	4,210
Deferred profit liability		156	125
Net liability for future policy benefits, per consolidated balance sheet		4,072	4,335			2,569
Less: Reinsurance recoverable on future policy benefits		103	107
Net liability for future policy benefits, after reinsurance recoverable		$ 3,969	$ 4,228
Weighted-average duration (years)		10 years 3 months 18 days	11 years
Accident and Health Insurance Product Line [Member] | Overseas General Insurance [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Net liability for future policy benefits		$ 718	$ 735
Deferred profit liability		0	0
Net liability for future policy benefits, per consolidated balance sheet		718	735			773
Less: Reinsurance recoverable on future policy benefits		33	38
Net liability for future policy benefits, after reinsurance recoverable		$ 685	$ 697
Weighted-average duration (years)		4 years 10 months 24 days	5 years 1 month 6 days
Insurance, Other | Segment Life [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Balance – beginning of period		$ 42	$ 30
Beginning balance at original discount rate				43	28
Effect of changes in cash flow assumptions				2	0
Effect of actual variances from expected experience				0	0
Adjusted beginning of period balance		45	28
Consolidation of Huatai Group		12
Acquisition of Cigna			23
Issuances		5	3
Interest accrual		1	1
Net premiums collected (1)	[1]	(15)	(9)
Other (including foreign exchange)		(18)	(4)
Ending balance at original discount rate		66	42
Effect of changes in discount rate assumptions		(1)	(1)
Balance – end of period		65	41
Balance – beginning of period		239	130
Beginning balance at original discount rate				250	122
Effect of changes in cash flow assumptions				3	11
Effect of actual variances from expected experience				$ 0	$ 0
Adjusted beginning of period balance		253	133
Consolidation of Huatai Group		298
Acquisition of Cigna			106
Issuances		5	3
Interest accrual		6	3
Benefits payments		(8)	(2)
Other (including foreign exchange)		178	102
Ending balance at original discount rate		732	141
Effect of changes in discount rate assumptions		(11)	(16)
Balance – end of period		721	125
Net liability for future policy benefits		656	84
Deferred profit liability		14	8
Net liability for future policy benefits, per consolidated balance sheet		670	92			$ 89
Less: Reinsurance recoverable on future policy benefits		21	0
Net liability for future policy benefits, after reinsurance recoverable		$ 649	$ 92
Weighted-average duration (years)		15 years 1 month 6 days	13 years 6 months

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