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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, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	$ 5,027		$ 5,027		$ 5,638
Finite-lived intangible assets, accumulated amortization	(3,667)		(3,667)		(3,622)
Finite-lived intangible assets, net amount	1,360		1,360		2,016
Intangible assets acquired			20
Amortization	(56)	$ (62)	(176)	$ (203)
Reclassification to held for sale			(501)
Foreign exchange			1
Client relationships [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	3,213		3,213		3,807
Finite-lived intangible assets, accumulated amortization	(2,522)		(2,522)		(2,514)
Finite-lived intangible assets, net amount	691		691		1,293
Intangible assets acquired			20
Amortization			(138)
Reclassification to held for sale			(484)
Foreign exchange			0
Software [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	744		744		729
Finite-lived intangible assets, accumulated amortization	(742)		(742)		(726)
Finite-lived intangible assets, net amount	2		2		3
Intangible assets acquired			0
Amortization			(2)
Reclassification to held for sale			0
Foreign exchange			1
Trademark and trade name [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	1,041		1,041		1,039
Finite-lived intangible assets, accumulated amortization	(374)		(374)		(342)
Finite-lived intangible assets, net amount	667		667		697
Intangible assets acquired			0
Amortization			(32)
Reclassification to held for sale			0
Foreign exchange			2
Other [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets, gross carrying amount	29		29		63
Finite-lived intangible assets, accumulated amortization	(29)		(29)		(40)
Finite-lived intangible assets, net amount	$ 0		0		$ 23
Intangible assets acquired			0
Amortization			(4)
Reclassification to held for sale			(17)
Foreign exchange			$ (2)