Future policy benefits (Undiscounted & discounted FPB) (Details) - Segment Life [Member] - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Liability for Future Policy Benefit, Activity [Line Items]
Discounted expected future benefit payments	$ 31,484	$ 30,635	$ 28,622	$ 27,462
Term Life Insurance
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefit payments	4,266		4,358
Undiscounted expected future gross premiums	6,595		7,291
Discounted expected future benefit payments	2,268	2,238	2,299	2,254
Discounted expected future gross premiums	4,460		3,909
Whole Life Insurance
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefit payments	29,099		24,834
Undiscounted expected future gross premiums	10,390		9,593
Discounted expected future benefit payments	12,429	12,057	10,568	10,063
Discounted expected future gross premiums	8,518		7,774
Accident and Health Insurance Product Line [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefit payments	26,695		26,475
Undiscounted expected future gross premiums	39,108		39,002
Discounted expected future benefit payments	15,930	15,693	15,225	14,650
Discounted expected future gross premiums	23,346		22,975
Insurance, Other
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefit payments	1,556		901
Undiscounted expected future gross premiums	478		94
Discounted expected future benefit payments	857	$ 647	530	$ 495
Discounted expected future gross premiums	$ 437		$ 83