Acquisitions Cash Paid for Acquisitions (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015
Business Combinations [Abstract]
Cost of investment: current-year acquisitions		$ 61.0	$ 8.3
Cost of investment: prior-year acquisition		37.2	31.8
Less: net cash acquired		(13.6)	(2.4)
Total cost of investment		84.6	37.7
Operating Expense	[1]	18.7	17.6
Total cash paid for acquisitions	[2]	103.3	55.3
Payments to acquire businesses, investing activity		47.9	5.9
Payments for previous acquisition, financing activity		$ 36.7	$ 31.8

[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 and are recorded in the operating section of the unaudited Consolidated Statements of Cash Flows.

[2] $47.9 of cash paid for acquisitions for the nine months ended September 30, 2016 is classified under the investing section of the unaudited Consolidated Statements of Cash Flows, as acquisitions, net of cash acquired. This amount relates to initial payments for new transactions. $36.7 of cash paid for acquisitions for the nine months ended September 30, 2016 is classified under the financing section of the unaudited Consolidated Statements of Cash Flows as acquisition-related payments. This amount relates to deferred payments and increases in our ownership interest for prior acquisitions.