Note 4 - Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Dividends and dividend equivalents	$ 21,289	$ 15,044
Stock rotation and sales returns	7,580	5,363
Income tax payable	5,527	7,018
Customer prepayments	2,927	2,520
Warranty	2,045	4,564
Commissions	1,661	1,369
Operating lease liabilities	1,158
Other	3,161	3,084
Total	$ 45,348	$ 38,962