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Long-Term Debt (Summary Of Long-Term Debt) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Sep. 13, 2019	Apr. 25, 2017
Debt Instrument [Line Items]
Capitalized lease obligations, vehicles, due through 2023	$ 2.4	$ 2.4
Less unamortized debt issuance costs	(5.2)	(5.5)
Total long-term debt	1,038.6	1,038.1
Less current maturities	51.2	38.8
Total long-term debt, net of current	987.4	999.3
Senior Notes \| 5.625% senior notes due 2027
Debt Instrument [Line Items]
Long-term debt, gross	$ 297.3	297.3
Stated interest rate	5.625%			5.625%
Unamortized discount	$ 2.7	2.7
Senior Notes \| 4.75% senior notes due 2029
Debt Instrument [Line Items]
Stated interest rate	4.75%
Secured Debt \| 4.75% senior notes due 2029 \| Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross	$ 494.1	493.9
Stated interest rate	4.75%		4.75%
Unamortized discount	$ 5.9	6.1
Secured Debt \| Term loan due 2023 \| Term facility
Debt Instrument [Line Items]
Long-term debt, gross	$ 250.0	$ 250.0
Effective interest rate	3.91%	4.31%