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Long-Term Debt (Summary Of Long-Term Debt) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Apr. 25, 2017	Aug. 14, 2013
Debt Instrument [Line Items]
Capitalized lease obligations, vehicles, due through 2021	$ 2.4	$ 2.5
Less unamortized debt issuance costs	(4.1)	(5.2)
Total long-term debt	867.8	880.8
Less current maturities	21.2	19.9
Total long-term debt, net of current	846.6	860.9
Senior Notes \| 6.00% senior notes due 2023
Debt Instrument [Line Items]
Long-term debt, gross	$ 495.7	495.0
Stated interest rate	6.00%			6.00%
Unamortized discount	$ 4.3	5.0
Senior Notes \| 5.625% senior notes due 2027
Debt Instrument [Line Items]
Long-term debt, gross	$ 296.8	296.5
Stated interest rate	5.625%		5.625%
Unamortized discount	$ 3.2	3.5
Secured Debt \| Term loan due 2020 \| Term facility
Debt Instrument [Line Items]
Long-term debt, gross	$ 77.0	$ 92.0
Effective interest rate	4.72%