Goodwill and Other Intangibles - Goodwill (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Roll Forward]
Beginning Balance	$ 669.3	$ 605.6
Goodwill Acquired	23.5	71.4
Foreign Exchange Rates	4.0	(7.7)
Ending Balance	696.8	669.3
CORPORATE & INSTITUTIONAL SERVICES
Goodwill [Roll Forward]
Beginning Balance	598.2	534.5
Goodwill Acquired	23.5	71.4
Foreign Exchange Rates	4.0	(7.7)
Ending Balance	625.7	598.2
WEALTH MANAGEMENT
Goodwill [Roll Forward]
Beginning Balance	71.1	71.1
Goodwill Acquired	0.0	0.0
Foreign Exchange Rates	0.0	0.0
Ending Balance	$ 71.1	$ 71.1