Restructuring Costs (Restructuring Activities) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Restructuring Reserve [Roll Forward]
Restructuring charges	$ 42	$ 53
Jardine Lloyd Thompson Group plc
Restructuring Reserve [Roll Forward]
Liability at beginning of period	130	146	$ 146
Restructuring charges	42		301
Cash payments	(88)		(271)
Non-cash charges	(2)		(46)
Liability at end of period	82		130
Jardine Lloyd Thompson Group plc | Severance
Restructuring Reserve [Roll Forward]
Liability at beginning of period	89	88	88
Restructuring charges	21		148
Cash payments	(62)		(147)
Non-cash charges	0		0
Liability at end of period	48		89
Jardine Lloyd Thompson Group plc | Real Estate Related Costs
Restructuring Reserve [Roll Forward]
Liability at beginning of period	39	56	56
Restructuring charges	10		96
Cash payments	(13)		(69)
Non-cash charges	(2)		(44)
Liability at end of period	34		39
Jardine Lloyd Thompson Group plc | Information Technology
Restructuring Reserve [Roll Forward]
Liability at beginning of period	0	0	0
Restructuring charges	5		15
Cash payments	(5)		(13)
Non-cash charges	0		(2)
Liability at end of period	0		0
Jardine Lloyd Thompson Group plc | Consulting and Other Outside Services
Restructuring Reserve [Roll Forward]
Liability at beginning of period	2	$ 2	2
Restructuring charges	6		42
Cash payments	(8)		(42)
Non-cash charges	0		0
Liability at end of period	$ 0		$ 2