Note 4 - Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts	$ 1,333	$ 1,099
Insurance and claims reserves	22,503	24,261
Compensation and employee benefits	2,973	2,355
Net operating loss and credit carryforwards	53,552	15,225
Net federal capital loss carryforward		1,826
Capital lease obligations	4,782	6,512
Investment in subsidiaries	6,660	1,540
Other	551	3,487
Valuation allowance	(5,826)	(3,393)	$ (3,530)	$ (3,583)
Total deferred tax assets	86,528	52,912
Property and equipment	97,073	56,570
Intangibles	8,007	8,392
Prepaid license fees	974	1,014
Other	452	2,566
Total deferred tax liabilities	106,506	68,542
Net deferred tax liability	$ 19,978	$ 15,630