Note 5 - Balance Sheet Components - Other Long-term Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred compensation plan assets	$ 46,146	$ 38,858
Operating lease ROU assets	3,719	2,863
Prepaid expense	2,340	2,687
Debt investment	2,861	3,138
Equity investment in a privately held company	3,400	0
Other	1,372	1,544
Total	$ 59,838	$ 49,090

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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Amount of lessee's right to use underlying asset under operating lease.

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