Note 12 - Derivatives - Fair Value of Derivative Assets and Liabilities (Details) - Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair value, derivative asset		$ 1,690
Fair value, derivative liabilities	15,402	5,713
Interest Rate Swap [Member] | Prepaid Expenses and Other Current Assets [Member]
Fair value, derivative asset		1,425
Interest Rate Swap [Member] | Accrued Liabilities [Member]
Fair value, derivative liabilities	2,931
Interest Rate Swap [Member] | Other Noncurrent Liabilities [Member]
Fair value, derivative liabilities	11,632	5,713
Natural Gas Contracts [Member] | Prepaid Expenses and Other Current Assets [Member]
Fair value, derivative asset		226
Natural Gas Contracts [Member] | Other Assets [Member]
Fair value, derivative asset		39
Natural Gas Contracts [Member] | Accrued Liabilities [Member]
Fair value, derivative liabilities	836
Natural Gas Contracts [Member] | Other Noncurrent Liabilities [Member]
Fair value, derivative liabilities	$ 3