Goodwill and Acquired Client Relationships (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
Changes in goodwill
Balance at the beginning of the period	$ 2,117.3
Goodwill acquired	222.4
Foreign currency translation	2.3
Balance at the end of the period	2,342.0
Mutual Fund
Changes in goodwill
Balance at the beginning of the period	785.0
Goodwill acquired	147.6
Foreign currency translation	(0.6)
Balance at the end of the period	932.0
Institutional
Changes in goodwill
Balance at the beginning of the period	1,071.4
Goodwill acquired	0.2
Foreign currency translation	1.9
Balance at the end of the period	1,073.5
High Net Worth
Changes in goodwill
Balance at the beginning of the period	260.9
Goodwill acquired	74.6
Foreign currency translation	1.0
Balance at the end of the period	$ 336.5