Supplemental Cash Flow Information (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017
Supplemental Cash Flow Elements [Abstract]
Payments of interest and commitment fees	$ 115.9	$ 80.0
Interest paid, capitalized	2.0	11.9
Incurred liabilities for fixed and intangible asset additions	$ 18.6	$ 23.2

Future cash outflow to pay for purchases of fixed assets that have occurred.

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