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	32,446			0	32,446	0	0	0
Other comprehensive income (loss)	10,960			0	0	0	10,960	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	(4,368)			0	(4,368)	0	0	0
Stock-based compensation activity (in shares)		247	247
Stock-based compensation activity	3,541			11,046	(62)	(7,443)	0	0
Payments of withholding taxes for stock-based compensation awards (in shares)		(87)	(87)
Payments of withholding taxes for stock-based compensation awards	(4,763)			0	0	(4,763)	0	0
Repurchase of shares (in shares)		(5)	(5)
Repurchase of shares	(199)			0	0	(199)	0	0
Directors' deferred compensation	145			35	0	607	0	(497)
Stock Issued During Period Value Directors Deferred Compensation, Shares		2	2
Ending balance (in shares) at Jun. 28, 2019		20,399
Ending balances (in Treasury shares) at Jun. 28, 2019			(6,749)
Ending balances at Jun. 28, 2019	594,785			245,785	576,211	(187,224)	(43,978)	3,991
Beginning balance (in shares) at Mar. 29, 2019		20,354
Beginning balances (in Treasury shares) at Mar. 29, 2019			(6,794)
Beginning balances at Mar. 29, 2019	566,877			241,480	562,941	(184,812)	(57,270)	4,538
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15,540			0	15,540	0	0	0
Other comprehensive income (loss)	9,996			0	0	0	9,996	0
Net pension curtailments and settlements	3,296			0	0	0	3,296	0
Cash dividends declared	(2,243)			0	(2,243)	0	0	0
Stock-based compensation activity (in shares)		55	55
Stock-based compensation activity	1,994			4,287	(27)	(2,266)	0	0
Payments of withholding taxes for stock-based compensation awards (in shares)		(12)	(12)
Payments of withholding taxes for stock-based compensation awards	(785)			0	0	(785)	0	0
Directors' deferred compensation	110			18	0	639	0	(547)
Stock Issued During Period Value Directors Deferred Compensation, Shares		2	2
Ending balance (in shares) at Jun. 28, 2019		20,399
Ending balances (in Treasury shares) at Jun. 28, 2019			(6,749)
Ending balances at Jun. 28, 2019	594,785			245,785	576,211	(187,224)	(43,978)	3,991
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	3,575			0	3,575	0	0	0
Other comprehensive income (loss)	(109)			0	0	0	(109)	0
Net pension curtailments and settlements	94
Cash dividends declared	(4,582)			0	(4,582)	0	0	0
Stock-based compensation activity (in shares)		110	110
Stock-based compensation activity	4,057			7,037	(78)	(2,902)	0	0
Payments of withholding taxes for stock-based compensation awards (in shares)		(36)	(36)
Payments of withholding taxes for stock-based compensation awards	(2,025)			0	0	(2,025)	0	0
Repurchase of shares (in shares)		(158)	(158)
Repurchase of shares	(6,766)			0	0	(6,766)	0	0
Directors' deferred compensation	113			45	0	(188)	0	256
Stock Issued During Period Value Directors Deferred Compensation, Shares		2	2
Ending balance (in shares) at Jun. 26, 2020		20,322
Ending balances (in Treasury shares) at Jun. 26, 2020			(6,826)
Ending balances at Jun. 26, 2020	604,940			256,756	588,803	(198,726)	(45,571)	3,678
Beginning balance (in shares) at Mar. 27, 2020		20,310
Beginning balances (in Treasury shares) at Mar. 27, 2020			(6,838)
Beginning balances at Mar. 27, 2020	596,478			253,967	584,505	(198,311)	(47,173)	3,490
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6,678			0	6,678	0	0	0
Other comprehensive income (loss)	1,602			0	0	0	1,602	0
Cash dividends declared	(2,337)			0	(2,337)	0	0	0
Stock-based compensation activity (in shares)		11	11
Stock-based compensation activity	2,473			2,775	(43)	(259)	0	0
Payments of withholding taxes for stock-based compensation awards (in shares)		0	0
Payments of withholding taxes for stock-based compensation awards	(10)			0	0	(10)	0	0
Directors' deferred compensation	56			14	0	(146)	0	188
Stock Issued During Period Value Directors Deferred Compensation, Shares		1	1
Ending balance (in shares) at Jun. 26, 2020		20,322
Ending balances (in Treasury shares) at Jun. 26, 2020			(6,826)
Ending balances at Jun. 26, 2020	$ 604,940			$ 256,756	$ 588,803	$ (198,726)	$ (45,571)	$ 3,678