Financial Instruments and Risk Management (Effect of Derivative Instruments on the Consolidated Statements of Operations Derivatives Not Designated as Hedging Instruments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	$ 47.7	$ (104.5)	$ (29.5)
Interest rate swaps | Other expense
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	0.0	0.0	(71.2)
Foreign currency forward contracts | Other expense
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	47.7	(104.5)	41.7
Cash conversion feature of Cash Convertible Notes | Other expense
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	0.0	0.0	1,853.5
Purchased cash convertible note hedge | Other expense
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	0.0	0.0	(1,853.5)
Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Hedging Items	$ 10.0	$ 10.0	$ (5.9)