Fair Value Measurement (Assets and Liabilities Measure at Fair Value on Recurring Basis using Level 3 Inputs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1,	$ 1,168.2	$ 1,058.0
Acquisitions	0.0	(4.0)
Change in fair value included in earnings	18.9	(3.5)
Other	(7.5)	0.7
Balance as of December 31,	$ 1,179.6	$ 1,051.2