Debt and Financing (Details) $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2017	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 1,000.8
Premium/(Discount), Debt	(2.1)
Debt Issuance Cost	(10.7)
Book Value	988.0
Book Value, Current Maturities	(17.7)			$ (16.8)
Par Value, Excluding Current Maturities	983.1
Premium (Discount)	(2.1)
Book Value, Excluding Current Maturities	970.3			980.3
Operating leases, future minimum payments due	298.8
Acquisition of property and equipment	(39.0)	$ (47.3)
Carrying Amount [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value	988.0			997.1
Fair Value [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value	954.8			999.0
Term Loan
Debt Instrument [Line Items]
Long-term Debt, Gross	635.2
Premium/(Discount), Debt	(2.1)
Debt Issuance Cost	(9.1)
Book Value	624.0
Debt Instrument, Gross, Current Maturities	(6.8)
Premium/(Discount), Current Maturities	0.0
Deferred Finance Costs, Current, Net	0.0
Book Value, Current Maturities	$ (6.8)
Stated Interest Rate	8.50%
Average Effective Interest Rate	8.70%
Term Loan | Carrying Amount [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value	$ 624.0			627.2
Term Loan | Fair Value [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value	622.6			638.1
Line of Credit [Member] | 2014 ABL Facility Credit Agreement [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	0.0
Premium/(Discount), Debt	0.0
Debt Issuance Cost	0.0
Book Value	0.0
Line of credit facility, total cash and availability	82.4
Secured Second A&R CDA [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	27.2
Premium/(Discount), Debt	0.0
Debt Issuance Cost	(0.1)
Book Value	$ 27.1
Average Effective Interest Rate	7.50%
Unsecured Second A&R CD [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 73.2
Premium/(Discount), Debt	0.0
Debt Issuance Cost	(0.4)
Book Value	$ 72.8
Average Effective Interest Rate	7.50%
Lease Financing Obligations [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 265.2
Premium/(Discount), Debt	0.0
Debt Issuance Cost	(1.1)
Book Value	264.1
Debt Instrument, Gross, Current Maturities	(10.9)
Premium/(Discount), Current Maturities	0.0
Deferred Finance Costs, Current, Net	0.0
Book Value, Current Maturities	$ (10.9)
Average Effective Interest Rate	12.00%
Lease Financing Obligations [Member] | Carrying Amount [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value	$ 264.1			268.6
Lease Financing Obligations [Member] | Fair Value [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value	233.8			259.1
Letter of Credit [Member] | 2014 ABL Facility Credit Agreement [Member]
Debt Instrument [Line Items]
Letters of credit outstanding, amount	359.7
Other Debt Obligations [Member] | Carrying Amount [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value	99.9			101.3
Other Debt Obligations [Member] | Fair Value [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value	$ 98.4			$ 101.8
Credit Agreement Amendment, September 2014
Debt Instrument [Line Items]
Debt Instrument, Total Leverage Ratio			3.61
Credit Agreement Amendment, January 31, 2017
Debt Instrument [Line Items]
Maximum Total Leverage Ratio, June 30, 2017	3.85
Maximum Total Leverage Ratio, September 30, 2017	3.75
Maximum Total Leverage Ratio, December 31, 2017	3.50
Maximum Total Leverage Ratio, March 31, 2018	3.5
Maximum Total Leverage Ratio, June 30, 2018	3.5
Maximum Total Leverage Ratio, September 30, 2018	3.5
Debt Instrument, Covenant, Maximum Total Leverage Ratio, Quarter Seven	3.50
Debt Instrument, Covenant, Maximum Total Leverage Ratio, Quarter Eight	3.25
Debt Instrument, Covenant, Maximum Total Leverage Ratio, Quarter Nine	3.25
Debt Instrument, Covenant, Maximum Total Leverage Ratio, Quarter Ten	3.00
Debt Instrument, Covenant, Maximum Total Leverage Ratio, Quarter Eleven	3.00
Debt Instrument, Covenant, Maximum Total Leverage Ratio, Quarter Twelve	3.00
Debt Instrument, Covenant, Maximum Total Leverage Ratio, Quarter Thirteen	2.75
Debt Instrument, Covenant, Maximum Total Leverage Ratio, Quarter Fourteen	2.75
Debt Instrument, Covenant, Maximum Total Leverage Ratio, Quarter Fifteen	2.75
Debt Instrument, Covenant, Maximum Total Leverage Ratio, Quarter Sixteen And Thereafter	2.75
2014 ABL Facility Credit Agreement [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity (Managed Accessibility)	$ 38.2
2014 ABL Facility Credit Agreement [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, total cash and availability	253.4
Revenue Equipment [Member]
Debt Instrument [Line Items]
Operating leases, future minimum payments due	$ 13.2
Operating lease term	5 years
London Interbank Offered Rate (LIBOR) | Term Loan
Debt Instrument [Line Items]
Floor interest rate	1.00%
Basis spread on variable rate	7.50%
Minimum [Member] | Secured Second A&R CDA [Member]
Debt Instrument [Line Items]
Stated Interest Rate	4.30%
Minimum [Member] | Unsecured Second A&R CD [Member]
Debt Instrument [Line Items]
Stated Interest Rate	4.30%
Minimum [Member] | Lease Financing Obligations [Member]
Debt Instrument [Line Items]
Stated Interest Rate	9.00%
Maximum [Member] | Secured Second A&R CDA [Member]
Debt Instrument [Line Items]
Stated Interest Rate	18.30%
Maximum [Member] | Unsecured Second A&R CD [Member]
Debt Instrument [Line Items]
Stated Interest Rate	18.30%
Maximum [Member] | Lease Financing Obligations [Member]
Debt Instrument [Line Items]
Stated Interest Rate	18.20%