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Goodwill and Other Intangible Assets - Changes in the Carrying Amount of Goodwill (Details) € in Millions, $ in Millions	3 Months Ended				12 Months Ended
	Mar. 31, 2022 USD ($)	Sep. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2021 EUR (€)	Dec. 31, 2021 USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 7,621		$ 7,683		$ 7,683
Acquisitions	3				66
Divestitures					(17)
Foreign currency translation	(42)				(111)
Ending balance	7,582				7,621
Investment Servicing
Goodwill [Roll Forward]
Beginning balance	7,354		7,413		7,413
Acquisitions	3				66
Divestitures					(17)
Foreign currency translation	(41)				(108)
Ending balance	7,316				7,354
Investment Servicing \| Fideuram Bank Luxembour
Goodwill [Roll Forward]
Payment for acquisition			258	€ 220
Investment Servicing \| Mercatus, Inc
Goodwill [Roll Forward]
Payment for acquisition		$ 88
Investment Management
Goodwill [Roll Forward]
Beginning balance	267		$ 270		270
Acquisitions	0				0
Divestitures					0
Foreign currency translation	(1)				(3)
Ending balance	$ 266				$ 267