Changes by Reporting Segment in Carrying Amounts of Goodwill, including Effect of Foreign Exchange Rates on Non-U.S.-Dollar-Denominated Balances (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Goodwill [Roll Forward]
Beginning Balance	$ 533.2	$ 540.7
Foreign Exchange Rates	(6.8)	(7.5)
Ending Balance	526.4	533.2
Corporate and Institutional Services
Goodwill [Roll Forward]
Beginning Balance	461.8	469.2
Foreign Exchange Rates	(6.7)	(7.4)
Ending Balance	455.1	461.8
Wealth Management
Goodwill [Roll Forward]
Beginning Balance	71.4	71.5
Foreign Exchange Rates	(0.1)	(0.1)
Ending Balance	$ 71.3	$ 71.4