Note 9 - Fair Value Measurement - Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Other current assets	$ 64,286	$ 42,199	$ 60,001
Fair Value, Recurring [Member]
Total assets	45,106	71,995	63,574
Interest rate swap	6,535	7,606	8,890
Total liabilities	6,535	7,606	8,890
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Total assets	44,000	71,995	63,574
Interest rate swap	0	0	0
Total liabilities	0	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Total assets	1,106	0	0
Interest rate swap	6,535	7,606	8,890
Total liabilities	6,535	7,606	8,890
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Total assets	0	0	0
Interest rate swap	0	0	0
Total liabilities	0	0	0
Fair Value, Recurring [Member] \| Money Market Funds [Member]
Cash equivalents	42,488	70,483	58,693
Fair Value, Recurring [Member] \| Money Market Funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Cash equivalents	42,488	70,483	58,693
Fair Value, Recurring [Member] \| Money Market Funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Cash equivalents	0	0	0
Fair Value, Recurring [Member] \| Money Market Funds [Member] \| Fair Value, Inputs, Level 3 [Member]
Cash equivalents	0	0	0
Fair Value, Recurring [Member] \| Restricted Cash [Member]
Other noncurrent assets	1,512	1,512	4,881
Fair Value, Recurring [Member] \| Restricted Cash [Member] \| Fair Value, Inputs, Level 1 [Member]
Other noncurrent assets	1,512	1,512	4,881
Fair Value, Recurring [Member] \| Restricted Cash [Member] \| Fair Value, Inputs, Level 2 [Member]
Other noncurrent assets	0	0	0
Fair Value, Recurring [Member] \| Restricted Cash [Member] \| Fair Value, Inputs, Level 3 [Member]
Other noncurrent assets	0	$ 0	$ 0
Fair Value, Recurring [Member] \| Derivative Financial Instruments, Assets [Member] \| Commodity Contract [Member]
Other current assets	1,106
Fair Value, Recurring [Member] \| Derivative Financial Instruments, Assets [Member] \| Fair Value, Inputs, Level 1 [Member] \| Commodity Contract [Member]
Commodity swap	0
Fair Value, Recurring [Member] \| Derivative Financial Instruments, Assets [Member] \| Fair Value, Inputs, Level 2 [Member] \| Commodity Contract [Member]
Other current assets	1,106
Fair Value, Recurring [Member] \| Derivative Financial Instruments, Assets [Member] \| Fair Value, Inputs, Level 3 [Member] \| Commodity Contract [Member]
Other current assets	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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- Definition

Fair value of all liability derivatives designated as cash flow hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624163-113959

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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Fair value of financial and nonfinancial obligations.

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- Definition

Amount of current assets classified as other.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.8)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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Fair value portion of other assets.

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