Note 15 - Fair Value Measurements (Details Textual) gal in Millions, $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($) $ / gal gal
Interest Rate Swap [Member]
Derivative, Number of Instruments Held, Total	2
Interest Rate Swap, One [Member]
Derivative, Notional Amount \| $	$ 53
Interest Rate Swap, Two [Member]
Derivative, Notional Amount \| $	$ 68
Fuel Hedge [Member]
Derivative, Nonmonetary Notional Amount, Volume (Gallon) \| gal	1
Fuel Hedge [Member] \| Minimum [Member]
Underlying, Derivative Volume (in USD per Gallon) \| $ / gal	1.79
Fuel Hedge [Member] \| Maximum [Member]
Underlying, Derivative Volume (in USD per Gallon) \| $ / gal	2.00

Nominal volume used to calculate payments on a derivative instrument.

No definition available.

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Namespace Prefix:	us-gaap_
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Period Type:	duration

- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959

+ Details

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- Definition

The number of derivative instruments of a particular group held by the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959

+ Details

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- Definition

Specified interest rate, security price, commodity price, foreign exchange rate, index of prices or rates for a derivative contract measured in volume but not the derivative contract itself.

+ References

No definition available.

+ Details

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