Future policy benefits (Rollforward) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Liability for Future Policy Benefit, Activity [Line Items]
Deferred profit liability		$ 1,908	$ 1,351
Net liability for future policy benefits, before reinsurance recoverable		16,690	14,375	$ 16,121
Less: Reinsurance recoverable on future policy benefits	[1]	267		$ 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)	185
Effect of actual variances from expected experience		(63)	(16)
Adjusted beginning of period balance		17,673	16,862
Issuances		1,160	1,059
Interest accrual		181	174
Net premiums collected (1)	[2]	(801)	(737)
Other (including foreign exchange)		(109)	73
Ending balance at original discount rate		18,104	17,431
Effect of changes in discount rate assumptions		29	(684)
Balance – end of period		18,133	16,747
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		(8)	194
Effect of actual variances from expected experience		(61)	(6)
Adjusted beginning of period balance		30,073	28,491
Issuances		1,160	1,059
Interest accrual		280	260
Benefits payments		(556)	(550)
Other (including foreign exchange)		(162)	163
Ending balance at original discount rate		30,795	29,423
Effect of changes in discount rate assumptions		689	(801)
Balance – end of period		31,484	28,622
Net liability for future policy benefits		13,351	11,875
Deferred profit liability		1,908	1,351
Net liability for future policy benefits, before reinsurance recoverable		15,259	13,226
Less: Reinsurance recoverable on future policy benefits		267	266
Net liability for future policy benefits, after reinsurance recoverable		$ 14,992	$ 12,960
Weighted average duration (years)		21 years 9 months 18 days	19 years 3 months 18 days
Other Segments
Liability for Future Policy Benefit, Activity [Line Items]
Net liability for future policy benefits, before reinsurance recoverable		$ 1,431	$ 1,149
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		7	(1)
Adjusted beginning of period balance		1,826	1,997
Issuances		65	65
Interest accrual		14	14
Net premiums collected (1)	[2]	(59)	(57)
Other (including foreign exchange)		(6)	(5)
Ending balance at original discount rate		1,840	2,014
Effect of changes in discount rate assumptions		(295)	(407)
Balance – end of period		1,545	1,607
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		10	3
Adjusted beginning of period balance		2,657	2,760
Issuances		65	65
Interest accrual		19	19
Benefits payments		(51)	(59)
Other (including foreign exchange)		(6)	30
Ending balance at original discount rate		2,684	2,815
Effect of changes in discount rate assumptions		(416)	(516)
Balance – end of period		2,268	2,299
Net liability for future policy benefits		723	692
Deferred profit liability		291	254
Net liability for future policy benefits, before reinsurance recoverable		1,014	946
Less: Reinsurance recoverable on future policy benefits		108	107
Net liability for future policy benefits, after reinsurance recoverable		$ 906	$ 839
Weighted average duration (years)		10 years 6 months	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		23	22
Adjusted beginning of period balance		4,322	4,037
Issuances		288	295
Interest accrual		32	27
Net premiums collected (1)	[2]	(311)	(310)
Other (including foreign exchange)		(19)	(4)
Ending balance at original discount rate		4,312	4,045
Effect of changes in discount rate assumptions		111	18
Balance – end of period		4,423	4,063
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		(10)	86
Effect of actual variances from expected experience		24	27
Adjusted beginning of period balance		11,256	10,104
Issuances		288	295
Interest accrual		90	74
Benefits payments		(78)	(87)
Other (including foreign exchange)		(32)	(2)
Ending balance at original discount rate		11,524	10,384
Effect of changes in discount rate assumptions		905	184
Balance – end of period		12,429	10,568
Net liability for future policy benefits		8,006	6,505
Deferred profit liability		1,351	904
Net liability for future policy benefits, before reinsurance recoverable		9,357	7,409
Less: Reinsurance recoverable on future policy benefits		45	45
Net liability for future policy benefits, after reinsurance recoverable		$ 9,312	$ 7,364
Weighted average duration (years)		27 years 10 months 24 days	25 years 7 months 6 days
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		(5)	109
Effect of actual variances from expected experience		(93)	(37)
Adjusted beginning of period balance		11,401	10,764
Issuances		599	697
Interest accrual		133	133
Net premiums collected (1)	[2]	(370)	(363)
Other (including foreign exchange)		(86)	82
Ending balance at original discount rate		11,677	11,313
Effect of changes in discount rate assumptions		212	(295)
Balance – end of period		11,889	11,018
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		2	100
Effect of actual variances from expected experience		(95)	(36)
Adjusted beginning of period balance		15,559	15,135
Issuances		599	697
Interest accrual		165	164
Benefits payments		(421)	(398)
Other (including foreign exchange)		(127)	114
Ending balance at original discount rate		15,775	15,712
Effect of changes in discount rate assumptions		155	(487)
Balance – end of period		15,930	15,225
Net liability for future policy benefits		4,041	4,207
Deferred profit liability		202	174
Net liability for future policy benefits, before reinsurance recoverable		4,243	4,381
Less: Reinsurance recoverable on future policy benefits		114	113
Net liability for future policy benefits, after reinsurance recoverable		$ 4,129	$ 4,268
Weighted average duration (years)		9 years 10 months 24 days	10 years 1 month 6 days
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		0	0
Adjusted beginning of period balance		124	64
Issuances		208	2
Interest accrual		2	0
Net premiums collected (1)	[2]	(61)	(7)
Other (including foreign exchange)		2	0
Ending balance at original discount rate		275	59
Effect of changes in discount rate assumptions		1	0
Balance – end of period		276	59
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		0	0
Adjusted beginning of period balance		601	492
Issuances		208	2
Interest accrual		6	3
Benefits payments		(6)	(6)
Other (including foreign exchange)		3	21
Ending balance at original discount rate		812	512
Effect of changes in discount rate assumptions		45	18
Balance – end of period		857	530
Net liability for future policy benefits		581	471
Deferred profit liability		64	19
Net liability for future policy benefits, before reinsurance recoverable		645	490
Less: Reinsurance recoverable on future policy benefits		0	1
Net liability for future policy benefits, after reinsurance recoverable		$ 645	$ 489
Weighted average duration (years)		23 years 6 months	15 years 1 month 6 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.