Restructuring Costs (Restructuring Activities) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Restructuring Reserve [Roll Forward]
Liability at beginning of period	$ 117	$ 130	$ 130
Restructuring charges	32	42	276
Cash payments	(57)		(270)
Non-cash charges	(1)		(19)
Liability at end of period	91		117
Severance
Restructuring Reserve [Roll Forward]
Liability at beginning of period	75	89	89
Restructuring charges	23		163
Cash payments	(45)		(177)
Non-cash charges	0		0
Liability at end of period	53		75
Real Estate Related Costs
Restructuring Reserve [Roll Forward]
Liability at beginning of period	42	39	39
Restructuring charges	9		66
Cash payments	(12)		(45)
Non-cash charges	(1)		(18)
Liability at end of period	38		42
Information Technology
Restructuring Reserve [Roll Forward]
Liability at beginning of period	0	0	0
Restructuring charges	0		25
Cash payments	0		(24)
Non-cash charges	0		(1)
Liability at end of period	0		0
Consulting and Other Outside Services
Restructuring Reserve [Roll Forward]
Liability at beginning of period	0	$ 2	2
Restructuring charges	0		22
Cash payments	0		(24)
Non-cash charges	0		0
Liability at end of period	$ 0		$ 0