Deferred acquisition costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Deferred Policy Acquisition Cost [Line Items]
Balance – beginning of period			$ 8,358
Amortization expense	$ (2,415)	$ (2,226)	(4,728)	$ (4,433)
Balance – end of period	9,437	7,812	9,437	7,812
Segment Life [Member]
Deferred Policy Acquisition Cost [Line Items]
Amortization expense	(319)	(300)	(629)	(594)
Overseas General Insurance [Member]
Deferred Policy Acquisition Cost [Line Items]
Amortization expense	(913)	(842)	(1,750)	(1,665)
Short-Duration Insurance, Other
Deferred Policy Acquisition Cost [Line Items]
Balance – end of period	4,085	3,646	4,085	3,646
Long-Duration Insurance, Other
Deferred Policy Acquisition Cost [Line Items]
Balance – end of period	5,352	4,166	5,352	4,166
Long-Duration Insurance, Other | Segment Life [Member]
Deferred Policy Acquisition Cost [Line Items]
Balance – beginning of period			4,066	3,185
Capitalizations			796	685
Amortization expense			(265)	(214)
Other (including foreign exchange)			109	(82)
Balance – end of period	4,706	3,574	4,706	3,574
Long-Duration Insurance, Other | Overseas General Insurance [Member]
Deferred Policy Acquisition Cost [Line Items]
Balance – end of period	646	592	646	592
Term Life Insurance | Segment Life [Member]
Deferred Policy Acquisition Cost [Line Items]
Balance – beginning of period			469	402
Capitalizations			115	98
Amortization expense			(73)	(58)
Other (including foreign exchange)			13	(6)
Balance – end of period	524	436	524	436
Universal Life | Segment Life [Member]
Deferred Policy Acquisition Cost [Line Items]
Balance – beginning of period			722	674
Capitalizations			69	70
Amortization expense			(41)	(39)
Other (including foreign exchange)			10	(25)
Balance – end of period	760	680	760	680
Whole Life Insurance | Segment Life [Member]
Deferred Policy Acquisition Cost [Line Items]
Balance – beginning of period			870	534
Capitalizations			224	170
Amortization expense			(25)	(17)
Other (including foreign exchange)			23	(14)
Balance – end of period	1,092	673	1,092	673
Accident and Health Insurance Product Line [Member] | Segment Life [Member]
Deferred Policy Acquisition Cost [Line Items]
Balance – beginning of period			1,681	1,301
Capitalizations			327	311
Amortization expense			(111)	(86)
Other (including foreign exchange)			51	(30)
Balance – end of period	1,948	1,496	1,948	1,496
Insurance, Other | Segment Life [Member]
Deferred Policy Acquisition Cost [Line Items]
Balance – beginning of period			324	274
Capitalizations			61	36
Amortization expense			(15)	(14)
Other (including foreign exchange)			12	(7)
Balance – end of period	$ 382	$ 289	$ 382	$ 289