Accounting Policies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 reporting_units	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Percentage Of Vie Partnership Investment Products Owned	1.00%
Fair value of recognized acquired assets	100.00%
Non controlling interest in acquisitions	100.00%
Recognized liabilities acquired	100.00%
Cash To Facilitate Trust Operations And Customer Transactions	$ 2.4	$ 2.9
European Sub Group Cash And Cash Equivalent	937.6	632.3
non-U.S. cash and cash equivalents	1,109.4	740.5
Cash deposits with clearing organizations	11.4	11.3
Reporting Units for Goodwill	1
Share Based Payment, Estimated Forfeitures, Percentage	3.00%
Percentage of Excess in Projected Benefit Obligation and Fair Value Assets To Be Amortized	10.00%
Advertising Costs	$ 38.6	$ 31.3	$ 31.9
Building [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life, Minimum	50 years
Software Development [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life, Minimum	5 years
Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life, Minimum	3 years
Intangible assets, useful life, years	2 years
Minimum [Member] | CLO [Member]
Property, Plant and Equipment [Line Items]
Reporting Period Lag Between Parent Company and Consolidated Entity	1 month
Maximum [Member]
Property, Plant and Equipment [Line Items]
Cash Equivalent, Maturity Period	3 months
Settlement Period for Fund and Investor Receivables	4 days
Amortization Period of Sales Commission of Share B Redemptions	6 years
Property, Plant and Equipment, Useful Life, Minimum	7 years
Intangible assets, useful life, years	12 years
Maximum [Member] | CLO [Member]
Property, Plant and Equipment [Line Items]
Reporting Period Lag Between Parent Company and Consolidated Entity	3 months