Note 5 - Long-term Debt - Interest Expense, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Gross interest costs	$ 3,217	$ 3,413	$ 9,861	$ 10,520
Less: capitalized interest costs	(65)	(74)	(218)	(452)
Interest expense	3,152	3,339	9,643	10,068
Interest income	(98)	(49)	(421)	(148)
Interest expense, net	$ 3,054	$ 3,290	$ 9,222	$ 9,920
Weighted-average interest rate on Credit Facility borrowings	2.50%	2.00%	2.30%	2.00%