CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Current Assets
Cash	$ 22,813	$ 38,492
Short-term investments	114,507	114,326
Trade receivables, net	55,988	45,031
Gross inventories (Note 4)	84,660	80,288
Less LIFO reserve	(48,113)	(46,341)
Less excess and obsolescence reserve	(3,566)	(2,527)
Net inventories	32,981	31,420
Prepaid expenses and other current assets	3,636	2,920
Total Current Assets	229,925	232,189
Property, plant and equipment	362,778	358,756
Less allowances for depreciation	(293,213)	(276,045)
Net property, plant and equipment	69,565	82,711
Deferred income taxes	2,939	2,969
Other assets	26,078	17,663
Total Assets	328,507	335,532
Current Liabilities
Trade accounts payable and accrued expenses	25,073	33,021
Contract liabilities with customers (Note 3)	3,640	7,477
Product liability	973	1,073
Employee compensation and benefits	13,561	20,729
Workers' compensation	5,465	5,551
Income taxes payable		3,340
Total Current Liabilities	48,712	71,191
Product liability	77	99
Lease liability (Note 5)	2,086
Contingent liabilities (Note 13)
Stockholders' Equity
Additional paid-in capital	37,108	33,291
Retained earnings	361,957	350,423
Less: Treasury stock - at cost 2019 - 6,709,898 shares 2018 - 6,665,398 shares	(145,591)	(143,595)
Total Stockholders' Equity	277,632	264,242
Total Liabilities and Stockholders' Equity	328,507	335,532
Nonvoting Common Stock [Member]
Stockholders' Equity
Common Stock
Common Stock [Member]
Stockholders' Equity
Common Stock	$ 24,158	$ 24,123