Long-Term Debt -Revolving Loan (Details) £ in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 GBP (£)	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Debt, short-term and long-term	$ 3,268.3		$ 3,268.3			$ 3,177.0
Net loss on extinguishments of long-term debt	0.0	$ (45.8)	(24.3)	$ (53.8)
Kelway Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt, short-term and long-term	0.0		0.0
Availability under Revolving Loan	75.6		75.6		£ 50.0
Revolving Loan [Member]
Debt Instrument [Line Items]
Debt, short-term and long-term	0.0		0.0			0.0
Undrawn letters of credit	2.1		2.1
Borrowing Base	1,412.4		1,412.4
Availability under Revolving Loan	905.9		905.9
Accounts Payable, Inventory Financing [Member]
Debt Instrument [Line Items]
Revolving Loan inventory financing agreement	353.2		353.2			$ 330.1
Accounts Payable, Inventory Financing [Member] | Revolving Loan [Member]
Debt Instrument [Line Items]
Amount owed under Revolving loan financing agreement	342.0		342.0
Floorplan sub-facility, variation between balance in financials and balance per financial intermediary due to timing differences in reporting	$ 11.2		$ 11.2