Note 8 - Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Insurance and claims	$ 10,269	$ 9,593
Net operating loss carryovers	25,849	10,260
Tax credits	10,942	11,985
Leased liability	15,668
Capital lease obligation	8,483
State bonus	6,576	5,938
Other	2,160	2,412
Valuation allowance	(385)	(63)
Total deferred tax assets	79,562	40,125
Deferred tax liabilities:
Property and equipment	(97,066)	(87,939)
Investment in partnership	(36,669)	(26,066)
Deferred fuel hedge		(73)
ROU Asset- leases	(15,280)
Other	(449)	(569)
Sec. 481(a) - capital leases	(7,462)
Prepaid expenses	(2,966)	(2,945)
Total deferred tax liabilities	(159,892)	(117,592)
Net deferred tax liability	$ (80,330)	$ (77,467)