Supplemental Cash Flow Information (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Payments of interest and commitment fees	$ 228.3	$ 168.3	$ 157.4
Capitalized interest	3.4	15.0	26.6
Cash paid for income taxes	0.2	1.0	1.3
Incurred liabilities for fixed and intangible asset additions	$ 9.4	$ 39.7	$ 33.7

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

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The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

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Amount of cash paid for interest, including, but not limited to, capitalized interest and payment to settle zero-coupon bond attributable to accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount; classified as operating and investing activities.

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Amount of cash paid for interest capitalized, classified as investing activity.

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