Financial Instruments and Risk Management (Effect Of Derivative Instruments on the Condensed Consolidated Statements of Operations Derivatives in Fair Value Hedging Relationships) (Details) - Fair Value Hedging Relationships - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Earnings on Derivatives	$ 0.0	$ 13.5	$ 22.1	$ 21.0
Amount of Gain (Loss) Recognized in Earnings on Hedged Items	0.0	(13.5)	(22.1)	(21.0)
Interest expense | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Earnings on Derivatives	0.0	13.5	22.1	21.0
Interest expense | 2023 Senior Notes (3.125% coupon)
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Earnings on Hedged Items	$ 0.0	$ (13.5)	$ (22.1)	$ (21.0)