Future policy benefits (Undiscounted & discounted FPB) (Details) - Segment Life [Member] - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Liability for Future Policy Benefit, Activity [Line Items]
Discounted expected future benefit payments	$ 28,622	$ 27,462	$ 23,052	$ 23,324
Term Life Insurance
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefit payments	4,358		4,041
Undiscounted expected future gross premiums	7,291		6,452
Discounted expected future benefit payments	2,299	2,254	2,440	2,321
Discounted expected future gross premiums	3,909		3,773
Whole Life Insurance
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefit payments	24,834		16,446
Undiscounted expected future gross premiums	9,593		6,895
Discounted expected future benefit payments	10,568	10,063	5,908	5,696
Discounted expected future gross premiums	7,774		5,398
Accident and Health Insurance Product Line [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefit payments	26,475		23,186
Undiscounted expected future gross premiums	39,002		33,809
Discounted expected future benefit payments	15,225	14,650	14,436	15,038
Discounted expected future gross premiums	22,975		20,766
Insurance, Other
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefit payments	901		342
Undiscounted expected future gross premiums	94		97
Discounted expected future benefit payments	530	$ 495	268	$ 269
Discounted expected future gross premiums	$ 83		$ 87