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		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	$ 5,531		$ 5,531		$ 5,677
Finite-lived intangible assets, accumulated amortization	(3,217)		(3,217)		(3,122)
Finite-lived intangible assets, net amount	2,314		2,314		2,555
Intangible assets acquired			65
Intangible asset disposals			(6)
Amortization	(71)	$ (85)	(239)	$ (285)
Foreign exchange			(61)
Client relationships [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	3,691		3,691		3,794
Finite-lived intangible assets, accumulated amortization	(2,186)		(2,186)		(2,118)
Finite-lived intangible assets, net amount	1,505		1,505		1,676
Intangible assets acquired			60
Intangible asset disposals			(1)
Amortization			(173)
Foreign exchange			(57)
Software [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	710		710		742
Finite-lived intangible assets, accumulated amortization	(692)		(692)		(701)
Finite-lived intangible assets, net amount	18		18		41
Intangible assets acquired			4
Intangible asset disposals			0
Amortization			(27)
Foreign exchange			0
Trademark and trade name [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	1,035		1,035		1,039
Finite-lived intangible assets, accumulated amortization	(286)		(286)		(257)
Finite-lived intangible assets, net amount	749		749		782
Intangible assets acquired			1
Intangible asset disposals			0
Amortization			(32)
Foreign exchange			(2)
Other [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	95		95		102
Finite-lived intangible assets, accumulated amortization	(53)		(53)		(46)
Finite-lived intangible assets, net amount	$ 42		42		$ 56
Intangible assets acquired			0
Intangible asset disposals			(5)
Amortization			(7)
Foreign exchange			$ (2)