Acquisitions - Estimated fair values of the assets and liabilities and noncontrolling interests assumed (Details) (USD $) In Millions, unless otherwise specified	Nov. 01, 2012
Initial Estimated Fair Value [Member]
Business Acquisition [Line Items]
Cash, including cash invested	$ 191.6
Investments of consolidated sponsored investment products	31.1
Indefinite-lived intangible assets	105.2
Definite-lived intangible assets	43.8
Goodwill	110.1
Other assets	28.0
Debt	(176.5)
Other liabilities	(21.6)
Noncontrolling interests	(38.2)
Total Identifiable Net Assets	273.5
Adjustments [Member]
Business Acquisition [Line Items]
Cash, including cash invested	0
Investments of consolidated sponsored investment products	0
Indefinite-lived intangible assets	(105.2)
Definite-lived intangible assets	41.2
Goodwill	64.0
Other assets	0
Debt	0
Other liabilities	0
Noncontrolling interests	0
Total Identifiable Net Assets	0
Revised Estimated Fair Value [Member]
Business Acquisition [Line Items]
Cash, including cash invested	191.6
Investments of consolidated sponsored investment products	31.1
Indefinite-lived intangible assets	0
Definite-lived intangible assets	85.0
Goodwill	174.1
Other assets	28.0
Debt	(176.5)
Other liabilities	(21.6)
Noncontrolling interests	(38.2)
Total Identifiable Net Assets	$ 273.5