Depreciation and Interest Charges on Property, Plant and Equipment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Property Plant And Equipment [Abstract]
Depreciation and amortization on PP&E	$ 15.0	$ 14.7	$ 29.6	$ 29.4
Interest charges capitalized (in construction in progress)	$ 0.1	$ 0.1	$ 0.4	$ 0.3