Goodwill and Other Intangibles - Goodwill (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
Beginning Balance	$ 707.2	$ 696.8
Goodwill Acquired	4.2
Foreign Exchange Rates	(5.2)	10.4
Ending Balance	706.2	707.2
Goodwill, Transfers		9.3
CORPORATE & INSTITUTIONAL SERVICES
Goodwill [Roll Forward]
Beginning Balance	626.7	616.4
Goodwill Acquired	4.2
Foreign Exchange Rates	(5.2)	10.3
Ending Balance	625.7	626.7
WEALTH MANAGEMENT
Goodwill [Roll Forward]
Beginning Balance	80.5	80.4
Goodwill Acquired	0.0
Foreign Exchange Rates	0.0	0.1
Ending Balance	$ 80.5	$ 80.5