Note K - Fair Value Measurements - Fair Value Measurements of Assets and Liabilities on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Money Market Funds [Member]
Money market mutual funds	$ 661	$ 2,998
Cash equivalents
Money market mutual funds	661	2,998
Money Market Funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Money market mutual funds	661	2,998
Cash equivalents
Money market mutual funds	661	2,998
Money Market Funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Money market mutual funds
Cash equivalents
Money market mutual funds
Money Market Funds [Member] \| Fair Value, Inputs, Level 3 [Member]
Money market mutual funds
Cash equivalents
Money market mutual funds
US Government-sponsored Enterprises Debt Securities [Member]
Short-term securities	2,028	786
Long-term securities	19,277	21,258
Cash equivalents
Short-term securities	2,028	786
Long-term marketable securities
Long-term securities	19,277	21,258
US Government-sponsored Enterprises Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Short-term securities
Long-term securities
Cash equivalents
Short-term securities
Long-term marketable securities
Long-term securities
US Government-sponsored Enterprises Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Short-term securities	2,028	786
Long-term securities	19,277	21,258
Cash equivalents
Short-term securities	2,028	786
Long-term marketable securities
Long-term securities	19,277	21,258
US Government-sponsored Enterprises Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Short-term securities
Long-term securities
Cash equivalents
Short-term securities
Long-term marketable securities
Long-term securities
Corporate Debt Securities [Member]
Short-term securities	24,988	18,430
Long-term securities	49,021	56,398
Cash equivalents
Short-term securities	24,988	18,430
Long-term marketable securities
Long-term securities	49,021	56,398
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Short-term securities
Long-term securities
Cash equivalents
Short-term securities
Long-term marketable securities
Long-term securities
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Short-term securities	24,988	18,430
Long-term securities	49,021	56,398
Cash equivalents
Short-term securities	24,988	18,430
Long-term marketable securities
Long-term securities	49,021	56,398
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Short-term securities
Long-term securities
Cash equivalents
Short-term securities
Long-term marketable securities
Long-term securities

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- References

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- Definition

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.

+ References

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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- Definition

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.

+ References

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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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