Note 6 - Business Segments and Sales of Products - Sales by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Sales by geographical area	$ 209,262	$ 160,484	$ 515,861	$ 448,458
CANADA
Sales by geographical area	80,410	88,610	89,998	258,708
KOREA, REPUBLIC OF
Sales by geographical area	78,152	33,683	129,939	109,184
JAPAN
Sales by geographical area	14,337	17,339	32,071	34,924
NETHERLANDS
Sales by geographical area	0	445	(923)	16,500
CHINA
Sales by geographical area	2,736	0	41,744	0
UNITED STATES
Sales by geographical area	33,627	20,407	223,032	29,142
Other Geographic Areas [Member]
Sales by geographical area	$ 209,262	$ 160,484	$ 515,861	$ 448,458