Note 3 - Marketable Securities and Time Deposits (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 56,855	$ 94,550
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	245	1,636
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	115	1,498
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	130	138
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Total	0
Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale	44,396	20,501	$ 21,499
Proceeds from Sale of Available-for-sale Securities, Total	25,064	5,113	19,226
Debt Securities, Available-for-sale, Realized Gain	4	26	7
Debt Securities, Available-for-sale, Realized Loss	77	$ 67	$ 57
Corporate Debt Securities [Member]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Total	$ 0

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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This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of realized gain 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 of realized loss 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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The amount by which the fair value of an investment in debt and equity securities categorized as Available-for-sale is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting.

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Amount of cash inflow from maturity, prepayment and call 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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The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

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