Note H - Derivative Financial Instruments (Details Textual) xbrli-pure in Thousands	12 Months Ended
Dec. 31, 2020 USD ($) T	Dec. 31, 2019
Derivative, Number of Instruments Held, Total		0
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred	$ 3,533,120
Not Designated as Hedging Instrument [Member]
Derivative, Number of Instruments Held, Total	0
Designated as Hedging Instrument [Member] \| Long [Member]
Derivative, Nonmonetary Notional Amount, Mass (US Ton) \| T	16,080
Designated as Hedging Instrument [Member] \| Long [Member] \| Minimum [Member]
Derivative, Term of Contract (Month)	60 days
Designated as Hedging Instrument [Member] \| Long [Member] \| Maximum [Member]
Derivative, Term of Contract (Month)	1 year 150 days
Designated as Hedging Instrument [Member] \| Short [Member]
Derivative, Nonmonetary Notional Amount, Mass (US Ton) \| T	32,120
Other Current Assets [Member]
Derivative, Collateral, Right to Reclaim Cash	$ 1,215,300
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	$ 1,227,940

Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
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- Definition

The estimated value of gains (losses), net anticipated to be transferred in the future from accumulated other comprehensive income into earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=121549185&loc=d3e80845-113994

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- Definition

Amount of right to receive cash collateral under master netting arrangements offset against derivative liabilities.

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- Definition

Nominal mass used to calculate payments on a derivative instrument.

+ References

No definition available.

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- Definition

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

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- Definition

Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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