Deferred acquisition costs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Deferred Policy Acquisition Cost [Line Items]
Balance – beginning of period	$ 8,358
Amortization expense	(2,313)	$ (2,207)
Balance – end of period	8,775	7,537
Segment Life [Member]
Deferred Policy Acquisition Cost [Line Items]
Amortization expense	(310)	(294)
Overseas General Insurance [Member]
Deferred Policy Acquisition Cost [Line Items]
Amortization expense	(837)	(823)
Short-Duration Insurance, Other
Deferred Policy Acquisition Cost [Line Items]
Balance – end of period	3,841	3,510
Long-Duration Insurance, Other
Deferred Policy Acquisition Cost [Line Items]
Balance – end of period	4,934	4,027
Long-Duration Insurance, Other | Segment Life [Member]
Deferred Policy Acquisition Cost [Line Items]
Balance – beginning of period	4,066	3,185
Capitalizations	415	339
Amortization expense	(129)	(104)
Other (including foreign exchange)	(26)	(9)
Balance – end of period	4,326	3,411
Long-Duration Insurance, Other | Overseas General Insurance [Member]
Deferred Policy Acquisition Cost [Line Items]
Balance – end of period	608	616
Term Life Insurance | Segment Life [Member]
Deferred Policy Acquisition Cost [Line Items]
Balance – beginning of period	469	402
Capitalizations	58	47
Amortization expense	(36)	(28)
Other (including foreign exchange)	4	(8)
Balance – end of period	495	413
Universal Life | Segment Life [Member]
Deferred Policy Acquisition Cost [Line Items]
Balance – beginning of period	722	674
Capitalizations	38	33
Amortization expense	(20)	(20)
Other (including foreign exchange)	(8)	1
Balance – end of period	732	688
Whole Life Insurance | Segment Life [Member]
Deferred Policy Acquisition Cost [Line Items]
Balance – beginning of period	870	534
Capitalizations	109	85
Amortization expense	(12)	(8)
Other (including foreign exchange)	(4)	(3)
Balance – end of period	963	608
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	170	158
Amortization expense	(54)	(41)
Other (including foreign exchange)	(16)	3
Balance – end of period	1,781	1,421
Insurance, Other | Segment Life [Member]
Deferred Policy Acquisition Cost [Line Items]
Balance – beginning of period	324	274
Capitalizations	40	16
Amortization expense	(7)	(7)
Other (including foreign exchange)	(2)	(2)
Balance – end of period	$ 355	$ 281