CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Apr. 03, 2021	Dec. 31, 2020
Current Assets
Cash	$ 24,137	$ 20,147
Short-term investments	121,997	121,007
Trade receivables, net	73,165	57,876
Gross inventories (Note 4)	80,215	80,487
Less LIFO reserve	(48,465)	(48,016)
Less excess and obsolescence reserve	(2,996)	(3,394)
Net inventories	28,754	29,077
Prepaid expenses and other current assets	4,195	6,266
Total Current Assets	252,248	234,373
Property, plant and equipment	399,176	393,843
Less allowances for depreciation	(330,356)	(323,110)
Net property, plant and equipment	68,820	70,733
Deferred income taxes		1,530
Other assets	43,061	41,622
Total Assets	364,129	348,258
Current Liabilities
Trade accounts payable and accrued expenses	34,934	37,078
Contract liabilities with customers (Note 3)		84
Product liability	944	1,052
Employee compensation and benefits	21,287	37,275
Workers' compensation	6,620	6,272
Income taxes payable	9,260
Total Current Liabilities	73,045	81,761
Product liability accrual	74	74
Lease liability (Note 5)	1,654	1,724
Deferred income taxes	876
Contingent liabilities (Note 13)
Stockholders' Equity
Additional paid-in capital	41,961	43,468
Retained earnings	367,816	342,615
Less: Treasury stock - at cost 2021 - 6,709,898 shares 2020 - 6,709,898 shares	(145,590)	(145,590)
Total Stockholders' Equity	288,480	264,699
Total Liabilities and Stockholders' Equity	364,129	348,258
Nonvoting Common Stock [Member]
Stockholders' Equity
Common Stock
Common Stock [Member]
Stockholders' Equity
Common Stock	$ 24,293	$ 24,206