Note 4 - Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Dividends and dividend equivalents	$ 27,846	$ 21,747
Stock rotation and sales returns	6,474	5,530
Accrued purchases of property and equipment	5,834	4,678
Income tax payable	2,462	2,435
Customer prepayments	5,221	3,412
Commissions	2,191	1,425
Warranty	1,144	1,139
Other	3,798	3,170
Total	56,110	44,790
Accrued Liabilities, Current [Member]
Operating lease liabilities	$ 1,140	$ 1,254