Expenses - Restructuring Reserve (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022
Restructuring Reserve [Roll Forward]
Beginning balance	$ 56	$ 73	$ 88	$ 45	$ 56	$ 74
Payments and Other Adjustments	(14)	(17)	(15)	(5)	(11)	(18)
Ending balance	42	56	73	40	45	56
Employee Related Costs
Restructuring Reserve [Roll Forward]
Beginning balance	53	69	83	40	51	68
Payments and Other Adjustments	(12)	(16)	(14)	(5)	(11)	(17)
Ending balance	41	53	69	35	40	51
Real Estate Actions
Restructuring Reserve [Roll Forward]
Beginning balance	3	4	5	5	5	6
Payments and Other Adjustments	(2)	(1)	(1)	0	0	(1)
Ending balance	$ 1	$ 3	$ 4	$ 5	$ 5	$ 5