Goodwill and Other Intangible Assets - Changes in the Net Carrying Amount of the Components of Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	$ 4,944		$ 4,901
Finite-lived intangible assets, accumulated amortization	(3,689)		(3,606)
Finite-lived intangible assets, net amount	1,255		1,295
Intangible assets acquired	1
Amortization	(48)	$ (60)
Foreign exchange	7
Client relationships [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	3,168		3,135
Finite-lived intangible assets, accumulated amortization	(2,559)		(2,497)
Finite-lived intangible assets, net amount	609		638
Intangible assets acquired	1
Amortization	(37)
Foreign exchange	7
Software [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	738		730
Finite-lived intangible assets, accumulated amortization	(735)		(727)
Finite-lived intangible assets, net amount	3		3
Intangible assets acquired	0
Amortization	0
Foreign exchange	0
Trademark and trade name [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	1,038		1,036
Finite-lived intangible assets, accumulated amortization	(395)		(382)
Finite-lived intangible assets, net amount	643		$ 654
Intangible assets acquired	0
Amortization	(11)
Foreign exchange	$ 0