Debt and Financing (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018 USD ($)	Mar. 31, 2018	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Par Value	$ 904.4
Discount	(8.5)
Debt Issuance Costs	(7.8)
Book Value	888.1
Book Value, Current Maturities	(25.1)		$ (30.6)
Par Value, Excluding Current Maturities	879.3
Premium (Discount)	(8.5)
Book Value, Excluding Current Maturities	863.0		875.5
Book Value
Debt Instrument [Line Items]
Long-term debt, fair value	888.1		906.1
Fair value
Debt Instrument [Line Items]
Long-term debt, fair value	921.6		929.9
Term Loan
Debt Instrument [Line Items]
Par Value	582.0
Discount	(8.5)
Debt Issuance Costs	(6.9)
Book Value	566.6
Par Value, Current Maturities	(18.0)
Discount, Current Maturities	0.0
Deferred Issuance Costs, Current	0.0
Book Value, Current Maturities	$ (18.0)
Average Effective Interest Rate	11.10%
Term Loan | Book Value
Debt Instrument [Line Items]
Long-term debt, fair value	$ 566.6		576.8
Term Loan | Fair value
Debt Instrument [Line Items]
Long-term debt, fair value	595.4		596.9
ABL Facility | 2014 ABL Facility Credit Agreement
Debt Instrument [Line Items]
Par Value	0.0
Discount	0.0
Debt Issuance Costs	0.0
Book Value	0.0
Line of credit facility, total cash and availability	73.9
Secured Second A&R CDA
Debt Instrument [Line Items]
Par Value	26.9
Discount	0.0
Debt Issuance Costs	(0.1)
Book Value	$ 26.8
Average Effective Interest Rate	7.90%
Unsecured Second A&R CDA
Debt Instrument [Line Items]
Par Value	$ 48.2
Discount	0.0
Debt Issuance Costs	(0.2)
Book Value	48.0
Par Value, Current Maturities	(1.5)
Discount, Current Maturities	0.0
Deferred Issuance Costs, Current	0.0
Book Value, Current Maturities	$ (1.5)
Average Effective Interest Rate	7.90%
Lease financing obligations
Debt Instrument [Line Items]
Par Value	$ 247.3
Discount	0.0
Debt Issuance Costs	(0.6)
Book Value	246.7
Par Value, Current Maturities	(5.6)
Discount, Current Maturities	0.0
Deferred Issuance Costs, Current	0.0
Book Value, Current Maturities	$ (5.6)
Average Effective Interest Rate	14.50%
Lease financing obligations | Book Value
Debt Instrument [Line Items]
Long-term debt, fair value	$ 246.7		254.6
Lease financing obligations | Fair value
Debt Instrument [Line Items]
Long-term debt, fair value	249.4		257.7
Letter of Credit [Member] | 2014 ABL Facility Credit Agreement
Debt Instrument [Line Items]
Letters of credit outstanding, amount	345.0
Other Debt Obligations | Book Value
Debt Instrument [Line Items]
Long-term debt, fair value	74.8		74.7
Other Debt Obligations | Fair value
Debt Instrument [Line Items]
Long-term debt, fair value	76.8		$ 75.3
2014 ABL Facility Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity (Managed Accessibility)	32.0
2014 ABL Facility Credit Agreement | ABL Facility
Debt Instrument [Line Items]
Line of credit facility, total cash and availability	$ 225.2
Term Loan Agreement
Debt Instrument [Line Items]
Maximum Total Leverage Ratio, September 30, 2018	3.5
Maximum Total Leverage Ratio, December 31, 2018	3.50
Maximum Total Leverage Ratio, March 31, 2019	3.25
Maximum Total Leverage Ratio, June 30, 2019	3.25
Maximum Total Leverage Ratio, September 30, 2019	3.25
Maximum Total Leverage Ratio, December 31, 2019	3.00
Maximum Total Leverage Ratio, March 31, 2020	3.00
Maximum Total Leverage Ratio, June 30, 2020	3.00
Maximum Total Leverage Ratio, September 30, 2020	2.75
Maximum Total Leverage Ratio, December 31, 2020	2.75
Maximum Total Leverage Ratio, March 31, 2021	2.75
Maximum Total Leverage Ratio, June 30, 2021 and thereafter	2.50
Total leverage ratio		3.13
London Interbank Offered Rate (LIBOR) | Term Loan
Debt Instrument [Line Items]
Floor interest rate	1.00%
Basis spread on variable rate	8.50%