Note 3 - Marketable Securities and Time Deposits - Marketable Debt Securities by Contractual Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Marketable debt securities, amortized cost	$ 87,024	$ 99,406
Marketable debt securities, unrealized gains	179	1
Marketable debt securities, unrealized losses	(245)	(1,636)
Marketable debt securities, estimated fair value	86,958	97,772
Due in One Year or Less [Member]
Marketable debt securities, amortized cost	24,033	27,442
Marketable debt securities, unrealized gains	55
Marketable debt securities, unrealized losses	(14)	(78)
Marketable debt securities, estimated fair value	24,074	27,364
Due after One Year to Five Years [Member]
Marketable debt securities, amortized cost	62,991
Marketable debt securities, unrealized gains	124
Marketable debt securities, unrealized losses	(231)
Marketable debt securities, estimated fair value	$ 62,884
Due After One Year to Six Years [Member]
Marketable debt securities, amortized cost		71,965
Marketable debt securities, unrealized gains		1
Marketable debt securities, unrealized losses		(1,558)
Marketable debt securities, estimated fair value		$ 70,408

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).

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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).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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