Cash Paid for Acquisitions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Business Acquisitions
Cost of investment	$ 182.6	[1]	$ 134.6	[1]	$ 91.4	[1]
Less: net cash acquired	(14.8)		(18.5)		(5.3)
Operating expense	3.2	[2]	0.5	[2]	3.0	[2]
Total cash paid for acquisitions	185.8		135.1		94.4
Acquisition-related payments	(37.1)		(71.5)		(29.5)
Acquisitions, including deferred payments, net of cash acquired	(145.5)		(63.1)		(61.9)
Cost of investment: current-year acquisitions
Business Acquisitions
Cost of investment	156.8		48.0		47.1
Cost of investment: prior-year acquisitions
Business Acquisitions
Cost of investment	$ 40.6		$ 105.1		$ 49.6

[1] Of the total cash paid, $37.1, $71.5 and $29.5 for the years ended December 31, 2012, 2011 and 2010, respectively, are classified under the financing section of the Consolidated Statements of Cash Flows within acquisition-related payments. These transactions relate to increases in our ownership interests in our consolidated subsidiaries as well as deferred payments for acquisitions that closed on or after January 1, 2009. Of the total cash paid, $145.5, $63.1 and $61.9 for the years ended December 31, 2012, 2011 and 2010, respectively, are classified under the investing section of the Consolidated Statements of Cash Flows within acquisitions, including initial payments for new transactions, net of cash acquired, and deferred payments for acquisitions that closed prior to January 1, 2009.

[2] Represents cash payments made that were either in excess of the contractual value or contingent upon the future employment of the former owners of acquired companies.