Acquisitions Cash Paid for Acquisitions (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash Paid for Acquisitions [Abstract]
Cost of investment: current-year acquisitions		$ 37.8	$ 97.3	$ 67.7
Cost of investment: prior-year acquisitions		53.1	14.0	28.5
Cash Acquired from Acquisition		(9.2)	(29.9)	(7.1)
Total cost of investment		81.7	81.4	89.1
Operating expense	[1]	18.4	3.4	2.0
Total cash paid for acquisitions	[2]	100.1	84.8	91.1
Payments for Previous Acquisitions, Financing Cash Flows		53.1	13.6	27.6
Payments for Initial Acquisitions, Investing Cash Flows		$ 28.6	$ 67.8	$ 61.5

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

[2] Of the total cash paid for acquisitions, $53.1, $13.6 and $27.6 for the years ended December 31, 2015, 2014 and 2013, respectively, are classified under the financing section of the Consolidated Statements of Cash Flows as acquisition-related payments. These amounts relate to deferred payments and increases in our ownership interest for prior acquisitions. $28.6, $67.8 and $61.5 for the years ended December 31, 2015, 2014 and 2013, respectively, are classified under the investing section of the Consolidated Statements of Cash Flows as acquisitions, net of cash acquired. These amounts relate to initial payments for new transactions.