Note K - Fair Value Measurements - Fair Value Measurements of Assets and Liabilities on Recurring Basis (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Derivative liabilities :	$ (20,000)
Fair Value, Inputs, Level 1 [Member]
Derivative liabilities :
Fair Value, Inputs, Level 2 [Member]
Derivative liabilities :	(20,000)
Fair Value, Inputs, Level 3 [Member]
Derivative liabilities :
Money Market Funds [Member]
Money market mutual funds	1,019,000	$ 2,998,000
Money Market Funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Money market mutual funds	1,019,000	2,998,000
Money Market Funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Money market mutual funds
Money Market Funds [Member] \| Fair Value, Inputs, Level 3 [Member]
Money market mutual funds
US Government-sponsored Enterprises Debt Securities [Member]
Short-term securities	1,695,000	786,000
Long-term securities	19,891,000	21,258,000
US Government-sponsored Enterprises Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Short-term securities
Long-term securities
US Government-sponsored Enterprises Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Short-term securities	1,695,000	786,000
Long-term securities	19,891,000	21,258,000
US Government-sponsored Enterprises Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Short-term securities
Long-term securities
Corporate Debt Securities [Member]
Short-term securities	23,647,000	18,430,000
Long-term securities	51,658,000	56,398,000
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Short-term securities
Long-term securities
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Short-term securities	23,647,000	18,430,000
Long-term securities	51,658,000	56,398,000
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Short-term securities
Long-term securities

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26626-111562

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (available-for-sale), classified as noncurrent.

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- Definition

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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Fair value, after the effects of master netting arrangements, of a financial liability or 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. Includes liabilities 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

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

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