Financial Instruments and Risk Management (Effect Of Derivative Instruments on the Condensed Consolidated Statements of Operations Derivatives in Fair Value Hedging Relationships) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Document Fiscal Year Focus	2018
Fair Value Hedging Relationships
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Earnings on Derivatives	$ (16.0)	$ (2.4)
Amount of Gain (Loss) Recognized in Earnings on Hedged Items	16.0	2.4
Fair Value Hedging Relationships | Interest expense | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Earnings on Derivatives	(16.0)	(2.4)
Fair Value Hedging Relationships | Interest expense | 2023 Senior Notes (3.125% coupon)
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Earnings on Hedged Items	$ 16.0	$ 2.4