Note E - Marketable Securities and Time Deposits - Marketable Debt Securities by Contractual Maturities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Marketable debt securities, amortized cost	$ 107,844	$ 112,885
Marketable debt securities, estimated fair value	107,602	$ 111,251
Debt Securities [Member]
Marketable debt securities, amortized cost	107,844
Marketable debt securities, unrealized gains	176
Marketable debt securities, unrealized losses	(418)
Marketable debt securities, estimated fair value	107,602
Debt Securities [Member] \| Due in One Year or Less [Member]
Marketable debt securities, amortized cost	30,188
Marketable debt securities, unrealized gains	49
Marketable debt securities, unrealized losses	(15)
Marketable debt securities, estimated fair value	30,222
Debt Securities [Member] \| Due after One Year to Five Years [Member]
Marketable debt securities, amortized cost	77,656
Marketable debt securities, unrealized gains	127
Marketable debt securities, unrealized losses	(403)
Marketable debt securities, estimated fair value	$ 77,380

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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