Note 15 - Acquisitions - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Sep. 28, 2015	Jul. 27, 2015	May 04, 2015	Feb. 09, 2015	Dec. 31, 2014
Goodwill	$ 290,191	$ 285,041					$ 265,145
Peterbilt of Las Vegas, Inc. [Member]
Property, equipment and capital lease assets			$ 17,241
Inventory			3,662
Prepaid expenses			295
Other			37
Accrued expenses			(960)
Capital lease obligations			(16,925)
Total			$ 3,350
Dallas Truck Center, Inc. [Member]
Property, equipment and capital lease assets				$ 2,308
Inventory				949
Total				$ 3,257
Yancey Truck Centers LLC [Member]
Property, equipment and capital lease assets					$ 11,316
Inventory					7,206
Other					85
Accrued expenses					(220)
Total					30,057
Goodwill					$ 11,670
Effingham Truck Sales Inc. [Member]
Property, equipment and capital lease assets						$ 7,090
Inventory						7,622
Prepaid expenses						80
Other						4
Total						25,261
Goodwill						9,159
Accounts receivable						$ 1,306