Note 4 - Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Dividends and dividend equivalents	$ 31,472	$ 26,435
Stock rotation and sales returns	6,240	6,005
Accrued purchases of property and equipment	5,339	5,841
Income tax payable	5,545	3,755
Customer prepayments	6,998	7,238
Commissions	1,252	1,107
Warranty	9,941	6,895
Other	5,627	4,278
Total	74,367	62,960
Accrued Liabilities, Current [Member]
Operating lease liabilities	$ 1,953	$ 1,406