Note 4 - Balance Sheet Components - Other Long-term Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Deferred compensation plan assets	$ 50,809	$ 46,146
Operating lease right-of-use (“ROU”) assets	6,094	3,719
Prepaid expense	2,453	2,340
Debt investment	2,582	2,861
Equity investment in a privately held company	3,249	3,400
Other	1,361	1,372
Total	$ 66,548	$ 59,838

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 noncurrent.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
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Carrying amount as of the balance sheet date of assets held under deferred compensation agreements.

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Amount of investment in equity security without readily determinable fair value.

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-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
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Amount of lessee's right to use underlying asset under operating lease.

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Amount of other miscellaneous assets expected to be realized or consumed after one year or normal operating cycle, if longer.

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