Business Combinations (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Acquisitions of new subsidiaries	13
Goodwill additions for acquisitions of new subsidiaries	$ 235.1
Accrued contingent purchase price payments included in goodwill	40.4
Goodwill recorded in acquisitions expected to be deductible for income tax purposes	45.9
Liability for contingent purchase price obligations	266.2	142.6
Liability for contingent purchase price obligations, current	$ 83.2	$ 32.8