Note 1 - Basis of Presentation and Accounting Policies (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Cost of Goods and Services Sold, Total	$ 110,992	$ 91,183	$ 301,234	$ 259,286
Nonoperating Income (Expense), Total	(201)	(483)	458	(1,390)
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	$ 431	395	$ 1,295	1,185
Revision of Prior Period, Adjustment [Member] | Cost of Sales Reclassified to Other (Expense) Income, Net [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total				200
Cost of Goods and Services Sold, Total		200
Nonoperating Income (Expense), Total				100
Revision of Prior Period, Adjustment [Member] | Selling, General and Administrative Expenses Reclassified to Other (Expense) Income, Net [Member]
Cost of Goods and Services Sold, Total		500
Nonoperating Income (Expense), Total				$ 100
Revision of Prior Period, Adjustment [Member] | Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total		$ (700)