Goodwill and Other Intangibles (Goodwill by Reporting Segment) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2026 USD ($)
Goodwill [Roll Forward]
Goodwill, Beginning Balance	$ 712.9
Foreign Exchange Rates	(3.4)
Goodwill, Ending Balance	709.5
ASSET SERVICING
Goodwill [Roll Forward]
Goodwill, Beginning Balance	632.5
Foreign Exchange Rates	(3.4)
Goodwill, Ending Balance	629.1
WEALTH MANAGEMENT
Goodwill [Roll Forward]
Goodwill, Beginning Balance	80.4
Foreign Exchange Rates	0.0
Goodwill, Ending Balance	$ 80.4