Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounting Policies [Line Items]
Advertising Expense	$ 32.8	$ 27.8	$ 25.3
General collection period for contracts-in-transit (in days)	14 days
Advertising credits and volume discounts	13.5	11.8	9.5
Long-term debt, excluding floor plan notes	$ 554.4	$ 466.0
Minimum [Member]
Accounting Policies [Line Items]
Loaner vehicle period of use before sale (in months)	6 months
Maximum [Member]
Accounting Policies [Line Items]
Loaner vehicle period of use before sale (in months)	12 months
8.375% Senior Subordinated Notes due 2020 | Senior Subordinated Notes [Member]
Accounting Policies [Line Items]
Stated interest rate of debt instrument	8.375%	8.375%