Note 4 - Marketable Securities - Investment in Marketable Securities (Details) $ in Thousands	Mar. 31, 2021 USD ($)
Amortized cost	$ 32,884
Gross unrealized gains	0
Gross unrealized losses	(20)
Fair value	32,982
Corporate Debt Securities [Member]
Amortized cost	17,578
Gross unrealized gains	0
Gross unrealized losses	(12)
Fair value	17,653
Commercial Paper [Member]
Amortized cost	7,768
Gross unrealized gains	0
Gross unrealized losses	0
Fair value	7,768
Money Market Funds [Member]
Amortized cost	3,751
Gross unrealized gains	0
Gross unrealized losses	0
Fair value	3,751
Debt Security, Corporate, Non-US [Member]
Amortized cost	2,856
Gross unrealized gains	0
Gross unrealized losses	(8)
Fair value	2,873
Municipal Bonds [Member]
Amortized cost	931
Gross unrealized gains	0
Gross unrealized losses	0
Fair value	$ 937

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), including amounts presented in cash and cash equivalents.

No definition available.

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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).

+ References

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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
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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
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