Supplemental Cash Flow Information (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Payments of interest and commitment fees	$ 43.0	$ 46.7
Interest paid, capitalized	1.4	6.0
Incurred liabilities for fixed and intangible asset additions	$ 20.6	$ 31.6