Note 11 - Business Segments, Sales of Products and Significant Customers - Sales by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Sales by geographical area	$ 674,549	$ 559,053	$ 583,758
UNITED STATES
Sales by geographical area	53,612	48,437	16,806
CANADA
Sales by geographical area	379,095	322,402	358,663
JAPAN
Sales by geographical area	48,841	42,885	58,475
NETHERLANDS
Sales by geographical area	38,420	0	0
KOREA, REPUBLIC OF
Sales by geographical area	154,581	145,263	80,183
CHINA
Sales by geographical area	$ 0	$ 66	$ 69,631