Business Combinations (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Acquisitions of new subsidiaries	12
Goodwill additions for acquisitions of new subsidiaries	$ 649.1
Accrued contingent purchase price payments included in goodwill	79.2
Goodwill recorded in acquisitions expected to be deductible for income tax purposes	89.7
Liability for contingent purchase price obligations	142.6	93.8
Liability for contingent purchase price obligations, current	$ 32.8	$ 16.9