Long-Term Debt -Revolving Loan (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Revolving Loan [Member]
Debt Instrument [Line Items]
Debt, short-term and long-term	$ 0	$ 0
Floorplan sub-facility, reserve	267,400,000
Revolving Commitment	900,000,000
Revolving loan financing agreement, percentage reserve for open orders	15.00%
Borrowing Base	1,098,800,000
Availability under Revolving Loan	631,400,000
Letter of Credit [Member]
Debt Instrument [Line Items]
Undrawn letters of credit	1,200,000
Accounts Payable, Inventory Financing [Member]
Debt Instrument [Line Items]
Floorplan sub-facility, reserve	8,800,000
Floorplan sub-facility, amount owed	258,600,000
Floorplan sub-facility, variation between balance in financials and balance per financial intermediary due to timing differences in reporting	$ 21,900,000