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		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	$ 5,617		$ 5,617		$ 5,677
Finite-lived intangible assets, accumulated amortization	(3,209)		(3,209)		(3,122)
Finite-lived intangible assets, net amount	2,408		2,408		2,555
Intangible assets acquired			61
Intangible asset disposals			(6)
Amortization	(83)	$ (97)	(168)	$ (200)
Foreign exchange			(34)
Client relationships [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	3,760		3,760		3,794
Finite-lived intangible assets, accumulated amortization	(2,176)		(2,176)		(2,118)
Finite-lived intangible assets, net amount	1,584		1,584		1,676
Intangible assets acquired			60
Intangible asset disposals			(1)
Amortization			(118)
Foreign exchange			(33)
Software [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	723		723		742
Finite-lived intangible assets, accumulated amortization	(705)		(705)		(701)
Finite-lived intangible assets, net amount	18		18		41
Intangible assets acquired			0
Intangible asset disposals			0
Amortization			(23)
Foreign exchange			0
Trademark and trade name [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	1,038		1,038		1,039
Finite-lived intangible assets, accumulated amortization	(277)		(277)		(257)
Finite-lived intangible assets, net amount	761		761		782
Intangible assets acquired			1
Intangible asset disposals			0
Amortization			(21)
Foreign exchange			(1)
Other [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	96		96		102
Finite-lived intangible assets, accumulated amortization	(51)		(51)		(46)
Finite-lived intangible assets, net amount	$ 45		45		$ 56
Intangible assets acquired			0
Intangible asset disposals			(5)
Amortization			(6)
Foreign exchange			$ 0