Income Taxes (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Valuation Allowance [Line Items]
Deferred Tax Liabilities, Net, Noncurrent	$ 216,200,000	$ 173,100,000
Operating Loss Carryforwards, Expiration Dates	2014 and 2033
Income Taxes (Textual) [Abstract]
U.S. federal statutory corporate tax rate	35.00%	35.00%	35.00%
Provision for income taxes	77,903,000	60,526,000	49,700,000
Effective tax rate	40.60%	37.70%	37.60%	37.80%
Long-term deferred tax assets	64,900,000	79,807,000
Number Of Dealerships Acquired		16
Provision for deferred taxes on undistributed earnings	20,900,000
No unrecognized tax benefits	0	0
2.25% Notes [Member]
Valuation Allowance [Line Items]
Debt interest rate	2.25%
3.00% Notes [Member]
Valuation Allowance [Line Items]
Debt interest rate	3.00%
UNITED KINGDOM
Income Taxes (Textual) [Abstract]
Number Of Dealerships Acquired	4	6
Foreign [Member]
Valuation Allowance [Line Items]
Deferred Tax Liabilities, Net, Noncurrent	27,500,000	0
State [Member]
Valuation Allowance [Line Items]
Operating Loss Carryforwards	210,400,000
Brazil [Member]
Valuation Allowance [Line Items]
Operating Loss Carryforwards	$ 38,400,000