Note 7 - Floor Plan Notes Payable and Lines of Credit (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Line of Credit Facility, Maximum Borrowing Capacity	$ 17,500,000
Floor Plan Notes Payable	$ 646,945,000	$ 854,758,000
Debt, Weighted Average Interest Rate	1.58%	1.47%
Line of Credit Amount Pledged to Secure Letters of Credit	$ 12,000,000
Line of Credit Facility, Remaining Borrowing Capacity	5,500,000
Long-term Line of Credit	0
BMO Harris Bank N.A. [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 875,000,000
Debt Instrument, Interest Rate, Effective Percentage	2.44%
Debt Instrument, Working Capital Fee Percentage	0.16%
Floor Plan Notes Payable	$ 548,100,000
BMO Harris Bank N.A. [Member] | If Termination Occurs on or Before January 1, 2018 [Member]
Debt Instrument, Prepayment Processing Fee, Percent	2.00%
BMO Harris Bank N.A. [Member] | If Termination Occurs after January 1, 2018 and on or Prior to July 1, 2018 [Member]
Debt Instrument, Prepayment Processing Fee, Percent	1.00%
BMO Harris Bank N.A. [Member] | IfTermination Occurs after July 1, 2018 and Prior to June 30, 2019 [Member]
Debt Instrument, Prepayment Processing Fee Amount	$ 500,000
BMO Harris Bank N.A. [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate	1.51%
Ford Motor Financing Agreement [Member]
Debt Instrument, Interest Rate, Effective Percentage	5.25%
Floor Plan Notes Payable	$ 66,400,000
Ford Motor Financing Agreement [Member] | Prime Rate [Member]
Debt Instrument, Basis Spread on Variable Rate	1.50%
Debt Instrument, Variable Rate, Minimum Reference Rate	3.75%