Note 12 - Business Segments, Sales of Products and Significant Customers - Sales by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Sales by geographical area	$ 708,253	$ 674,549	$ 559,053
UNITED STATES
Sales by geographical area	292,704	53,612	48,437
CANADA
Sales by geographical area	145,670	379,095	322,402
JAPAN
Sales by geographical area	39,418	48,841	42,885
NETHERLANDS
Sales by geographical area	(923)	38,420	0
KOREA, REPUBLIC OF
Sales by geographical area	165,302	154,581	145,263
CHINA
Sales by geographical area	$ 66,082	$ 0	$ 66