Note 10 - Reserves - Allowance for Doubtful Accounts and Reserves for Environmental Liabilities (Details) - SEC Schedule, 12-09, Allowance, Credit Loss [Member] - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Balance at beginning of year	$ 40	$ 57
Increase
Decrease	(6)	(17)
Balance at end of year	$ 34	$ 40

Amount of valuation and qualifying accounts and reserves.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

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- Definition

Amount of increase in valuation and qualifying accounts and reserves from charge to cost and expense.

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- Definition

Amount of decrease in valuation and qualifying accounts and reserves.

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