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, 2022	Mar. 31, 2021	Dec. 31, 2021
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	$ 5,685		$ 5,677
Finite-lived intangible assets, accumulated amortization	(3,193)		(3,122)
Finite-lived intangible assets, net amount	2,492		2,555
Intangible assets acquired	34
Intangible asset disposals	(5)
Amortization	(85)	$ (103)
Foreign exchange	(7)
Client relationships [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	3,811		3,794
Finite-lived intangible assets, accumulated amortization	(2,166)		(2,118)
Finite-lived intangible assets, net amount	1,645		1,676
Intangible assets acquired	34
Intangible asset disposals	0
Amortization	(60)
Foreign exchange	(5)
Software [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	736		742
Finite-lived intangible assets, accumulated amortization	(705)		(701)
Finite-lived intangible assets, net amount	31		41
Intangible assets acquired	0
Intangible asset disposals	0
Amortization	(10)
Foreign exchange	0
Trademark and trade name [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	1,038		1,039
Finite-lived intangible assets, accumulated amortization	(267)		(257)
Finite-lived intangible assets, net amount	771		782
Intangible assets acquired	0
Intangible asset disposals	0
Amortization	(11)
Foreign exchange	0
Other [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	100		102
Finite-lived intangible assets, accumulated amortization	(55)		(46)
Finite-lived intangible assets, net amount	45		$ 56
Intangible assets acquired	0
Intangible asset disposals	(5)
Amortization	(4)
Foreign exchange	$ (2)