Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Shares	Common Shares Held In Treasury	Common Stock	Retained Earnings	Common Stock In Treasury	Accumulated Other Comprehensive Income (Loss)	Other Equity
Beginning balance (in shares) at Dec. 31, 2018		20,242
Beginning balances (in Treasury shares) at Dec. 31, 2018			(6,906)
Beginning balances at Dec. 31, 2018	$ 553,906			$ 234,704	$ 548,374	$ (175,426)	$ (58,234)	$ 4,488
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	35,909			0	35,909	0	0	0
Other comprehensive income (loss)	11,080			0	0	0	11,080	0
Net pension curtailments and settlements	3,296			0	0	0	(3,296)	0
Cumulative Effect of Accounting Change	(179)			0	(179)	0	0	0
Cash dividends declared	(6,612)			0	(6,612)	0	0	0
Stock-based compensation activity (in shares)		252	252
Stock-based compensation activity	5,230			12,882	(83)	(7,569)	0	0
Payments of withholding taxes for stock-based compensation awards (in shares)		(89)	(89)
Payments of withholding taxes for stock-based compensation awards	(4,832)			0	0	(4,832)	0	0
Repurchase of shares (in shares)		(5)	(5)
Repurchase of shares	(199)			0	0	(199)	0	0
Directors' deferred compensation	197			65	0	562	0	(430)
Stock Issued During Period Value Directors Deferred Compensation, Shares		3	3
Ending balance (in shares) at Sep. 27, 2019		20,403
Ending balances (in Treasury shares) at Sep. 27, 2019			(6,745)
Ending balances at Sep. 27, 2019	597,796			247,651	577,409	(187,464)	(43,858)	4,058
Beginning balance (in shares) at Jun. 28, 2019		20,399
Beginning balances (in Treasury shares) at Jun. 28, 2019			(6,749)
Beginning balances at Jun. 28, 2019	594,785			245,785	576,211	(187,224)	(43,978)	3,991
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	3,463			0	3,463	0	0	0
Other comprehensive income (loss)	120			0	0	0	120	0
Cash dividends declared	(2,244)			0	(2,244)	0	0	0
Stock-based compensation activity (in shares)		5	5
Stock-based compensation activity	1,689			1,836	(21)	(126)	0	0
Payments of withholding taxes for stock-based compensation awards (in shares)		(2)	(2)
Payments of withholding taxes for stock-based compensation awards	(69)			0	0	(69)	0	0
Directors' deferred compensation	52			30	0	(45)	0	67
Stock Issued During Period Value Directors Deferred Compensation, Shares		1	1
Ending balance (in shares) at Sep. 27, 2019		20,403
Ending balances (in Treasury shares) at Sep. 27, 2019			(6,745)
Ending balances at Sep. 27, 2019	597,796			247,651	577,409	(187,464)	(43,858)	4,058
Beginning balance (in shares) at Dec. 31, 2019		20,404
Beginning balances (in Treasury shares) at Dec. 31, 2019			(6,744)
Beginning balances at Dec. 31, 2019	610,677			249,674	589,888	(186,845)	(45,462)	3,422
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	10,071			0	10,071	0	0	0
Other comprehensive income (loss)	2,681			0	0	0	2,681	0
Net pension curtailments and settlements	94
Cash dividends declared	(6,920)			0	(6,920)	0	0	0
Stock-based compensation activity (in shares)		117	117
Stock-based compensation activity	4,080			7,272	(59)	(3,133)	0	0
Payments of withholding taxes for stock-based compensation awards (in shares)		(39)	(39)
Payments of withholding taxes for stock-based compensation awards	(2,212)			0	0	(2,212)	0	0
Repurchase of shares (in shares)		(158)	(158)
Repurchase of shares	(6,766)			0	0	(6,766)	0	0
Directors' deferred compensation	170			73	0	(229)	0	326
Stock Issued During Period Value Directors Deferred Compensation, Shares		3	3
Ending balance (in shares) at Sep. 25, 2020		20,327
Ending balances (in Treasury shares) at Sep. 25, 2020			(6,821)
Ending balances at Sep. 25, 2020	611,781			257,019	592,980	(199,185)	(42,781)	3,748
Beginning balance (in shares) at Jun. 26, 2020		20,322
Beginning balances (in Treasury shares) at Jun. 26, 2020			(6,826)
Beginning balances at Jun. 26, 2020	604,940			256,756	588,803	(198,726)	(45,571)	3,678
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6,496			0	6,496	0	0	0
Other comprehensive income (loss)	2,790			0	0	0	2,790	0
Cash dividends declared	(2,338)			0	(2,338)	0	0	0
Stock-based compensation activity (in shares)		7	7
Stock-based compensation activity	23			235	19	(231)	0	0
Payments of withholding taxes for stock-based compensation awards (in shares)		(3)	(3)
Payments of withholding taxes for stock-based compensation awards	(187)			0	0	(187)	0	0
Directors' deferred compensation	57			28	0	(41)	0	70
Stock Issued During Period Value Directors Deferred Compensation, Shares		1	1
Ending balance (in shares) at Sep. 25, 2020		20,327
Ending balances (in Treasury shares) at Sep. 25, 2020			(6,821)
Ending balances at Sep. 25, 2020	$ 611,781			$ 257,019	$ 592,980	$ (199,185)	$ (42,781)	$ 3,748