Future policy benefits (Undiscounted & discounted FPB) (Details) - Segment Life [Member] - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
Liability for Future Policy Benefit, Activity [Line Items]
Discounted expected future benefit payments	$ 33,524	$ 30,635	$ 28,536	$ 27,462
Term Life Insurance
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefit payments	4,563		4,334
Undiscounted expected future gross premiums	7,094		7,223
Discounted expected future benefit payments	2,344	2,238	2,264	2,254
Discounted expected future gross premiums	4,775		4,776
Whole Life Insurance
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefit payments	30,751		25,052
Undiscounted expected future gross premiums	10,841		9,555
Discounted expected future benefit payments	13,407	12,057	10,659	10,063
Discounted expected future gross premiums	8,929		7,744
Accident and Health Insurance Product Line [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefit payments	28,274		26,037
Undiscounted expected future gross premiums	41,427		38,166
Discounted expected future benefit payments	16,781	15,693	15,058	14,650
Discounted expected future gross premiums	24,697		22,556
Insurance, Other
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefit payments	1,754		956
Undiscounted expected future gross premiums	570		174
Discounted expected future benefit payments	992	$ 647	555	$ 495
Discounted expected future gross premiums	$ 527		$ 155