Accumulated Other Comprehensive (Loss) (Components of Accumulated Other Comprehensive Income (Loss)) (Parenthetical) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	$ 1.8	$ 1.0
AFI [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Separation of AFI, tax (benefit)		(37.8)
Derivative Gain (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	1.2	2.5
Pension And Postretirement Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	$ 0.6	(1.5)
Pension And Postretirement Adjustments [Member] | AFI [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Separation of AFI, tax (benefit)		$ (37.8)