Note 11 - Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Inventory	$ 2,082	$ 1,522
Environmental	3,656	3,635
Net operating loss carryforwards	12,347	11,447
Employee benefits	9,512	11,245
Property, plant and equipment	11,581	5,007
Other	4,332	3,712
Total gross deferred tax assets	43,510	36,568
Valuation allowance	(12,263)	(11,824)
Total deferred tax assets	31,247	24,744
Deferred tax liabilities:
Property, plant and equipment	(69,337)	(15,275)
Intangibles and other	(14,536)	(8,537)
Foreign tax allocation reserve	(2,527)	(2,710)
Other	(714)	(2,830)
Total deferred tax liabilities	(87,114)	(29,352)
Net deferred tax liability	(55,867)	(4,608)
Classified as follows in the consolidated balance sheet:
Non-current deferred tax asset	1,409	3,198
Non-current deferred tax liability	(57,276)	(7,806)
Net deferred tax liability	$ (55,867)	$ (4,608)