Note 6 - Business Segments and Sales of Products - Sales by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Sales by geographical area	$ 135,245	$ 155,093
CANADA
Sales by geographical area	54,333	92,872
KOREA, REPUBLIC OF
Sales by geographical area	26,607	49,300
JAPAN
Sales by geographical area	6,121	8,350
CHINA
Sales by geographical area	13,921	0
UNITED STATES
Sales by geographical area	35,185	4,571
Other Geographic Areas [Member]
Sales by geographical area	$ (922)	$ 0