Restructuring Costs (Restructuring Activities) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Restructuring Reserve [Roll Forward]
Liability at beginning of period			$ 130	$ 146	$ 146
Restructuring charges	$ 54	$ 52	140	170	301
Cash payments			(195)		(271)
Non-cash charges			(9)		(46)
Liability at end of period	66		66		130
Severance
Restructuring Reserve [Roll Forward]
Liability at beginning of period			89	88	88
Restructuring charges			63		148
Cash payments			(123)		(147)
Non-cash charges			0		0
Liability at end of period	29		29		89
Real Estate Related Costs
Restructuring Reserve [Roll Forward]
Liability at beginning of period			39	56	56
Restructuring charges			41		96
Cash payments			(34)		(69)
Non-cash charges			(9)		(44)
Liability at end of period	37		37		39
Information Technology
Restructuring Reserve [Roll Forward]
Liability at beginning of period			0	0	0
Restructuring charges			19		15
Cash payments			(19)		(13)
Non-cash charges			0		(2)
Liability at end of period	0		0		0
Consulting and Other Outside Services
Restructuring Reserve [Roll Forward]
Liability at beginning of period			2	$ 2	2
Restructuring charges			17		42
Cash payments			(19)		(42)
Non-cash charges			0		0
Liability at end of period	$ 0		$ 0		$ 2