Consolidated Statements of Income - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 25, 2020	Sep. 27, 2019	Sep. 25, 2020	Sep. 27, 2019
Income Statement [Abstract]
Net sales	$ 287,171,000	$ 305,979,000	$ 836,585,000	$ 905,263,000
Cost of sales	240,531,000	240,748,000	696,280,000	701,126,000
Gross margin	46,640,000	65,231,000	140,305,000	204,137,000
Selling, general, and administrative expense	35,696,000	35,812,000	99,292,000	115,767,000
Research and development expense	5,417,000	5,262,000	14,104,000	13,064,000
Goodwill impairment charges	0	11,560,000	9,053,000	11,560,000
Asset impairment charges	0	2,581,000	1,713,000	2,581,000
Restructuring expense	2,593,000	785,000	7,144,000	785,000
Other - net	2,221,000	2,942,000	4,143,000	9,954,000
Operating profit	713,000	6,289,000	4,856,000	50,426,000
Other non-operating (income) expense - net	(1,076,000)	127,000	(2,871,000)	3,484,000
Interest Expense-net	1,334,000	436,000	2,839,000	1,402,000
Income before income taxes	455,000	5,726,000	4,888,000	45,540,000
Income tax (benefit) expense	(6,041,000)	2,263,000	(5,183,000)	9,631,000
Net income	$ 6,496,000	$ 3,463,000	$ 10,071,000	$ 35,909,000
Basic earnings per share:
Net income per share of common stock (in dollars per share)	$ 0.32	$ 0.17	$ 0.50	$ 1.76
Diluted earnings per share:
Net income per share of common stock (in dollars per share)	$ 0.32	$ 0.17	$ 0.49	$ 1.74
Weighted-average number of shares of common stock outstanding:
Basic (in shares)	20,325	20,401	20,342	20,351
Diluted (in shares)	20,592	20,677	20,595	20,645