Note 12 - Derivatives - Cash Settlements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Derivative, Additional Cash Settlements Received (Paid) on Hedge	$ 342	$ 585
Cash Flow Hedging [Member] | Natural Gas Contracts [Member]
Derivative, Additional Cash Settlements Received (Paid) on Hedge	(651)	426
Cash Flow Hedging [Member] | Interest Rate Swap [Member]
Derivative, Additional Cash Settlements Received (Paid) on Hedge	$ 993	$ 159