Inventory Financing Agreements (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Inventory Financing Agreements [Line Items]
Accounts payable-inventory financing	$ 299.7	$ 256.6
Accounts Payable, Inventory Financing [Member]
Inventory Financing Agreements [Line Items]
Revolving Loan inventory financing agreement	298.8	256.1
Other inventory financing agreements	0.9	0.5
Accounts payable-inventory financing	299.7	256.6
Previous Revolving Credit Facility [Member] | Accounts Payable, Inventory Financing [Member]
Inventory Financing Agreements [Line Items]
Floorplan sub-facility	$ 400.0