Note 11 - 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, 2019	Dec. 31, 2018
Balance at beginning of year	$ 34	$ 40
Increase	1
Decrease		(6)
Balance at end of year	$ 35	$ 34