Note 11 - Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Inventory	$ 2,769	$ 3,032
Foreign tax credit carryforwards		3,990
Environmental	5,776	2,795
Net operating loss carryforwards	13,272	7,930
Employee benefits	16,155	14,978
Alternative minimum tax credit carryforwards		1,306
Property, plant and equipment	4,448	4,188
Other	7,352	6,234
Total gross deferred tax assets	49,772	44,453
Valuation allowance	(11,459)	(9,863)
Total deferred tax assets	38,313	34,590
Deferred tax liabilities:
Property, plant and equipment	(17,709)	(11,472)
Intangibles and other	(10,583)	(8,192)
Unremitted foreign earnings	(635)	(208)
Foreign tax allocation reserve	(2,471)	(2,071)
Other	(775)	(1,123)
Total deferred tax liabilities	(32,173)	(23,066)
Net deferred tax assets	6,140	11,524
Classified as follows in the consolidated balance sheet:
Non-current deferred tax asset	13,061	19,259
Non-current deferred tax liability	(6,921)	(7,735)
Total	$ 6,140	$ 11,524