Accumulated Other Comprehensive (Loss) (Components of Accumulated Other Comprehensive Income (Loss)) (Parenthetical) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss) before reclassifications, tax expense	$ 0.9	$ 4.1
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	$ 0.9	3.9
Pension And Postretirement Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss) before reclassifications, tax expense		0.2
Pension And Postretirement Adjustments [Member] | AFI [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Separation of AFI, tax (benefit)		$ (37.8)