Goodwill and Other Intangibles - Goodwill (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Beginning Balance	$ 696.8	$ 669.3
Goodwill Acquired		23.5
Foreign Exchange Rates	10.4	4.0
Ending Balance	707.2	696.8
CORPORATE & INSTITUTIONAL SERVICES
Goodwill [Roll Forward]
Beginning Balance	625.7	598.2
Goodwill Acquired		23.5
Foreign Exchange Rates	10.3	4.0
Ending Balance	636.0	625.7
WEALTH MANAGEMENT
Goodwill [Roll Forward]
Beginning Balance	71.1	71.1
Goodwill Acquired		0.0
Foreign Exchange Rates	0.1	0.0
Ending Balance	$ 71.2	$ 71.1