Accumulated Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Income (Loss)) (Parenthetical) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	$ 1.0	$ (0.6)	$ 4.8	$ (1.2)
Derivative Gain (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	1.1	(0.7)	5.9	(1.5)
Pension And Postretirement Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	$ (0.1)	$ 0.1	$ (1.1)	$ 0.3