Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock [Member]	Total
Balance at Dec. 28, 2019	$ 41,395	$ 433,190	$ 42,517	$ (34,030)	$ 0	$ 483,072
Net income (loss)	0	0	(13,801)	0	0	(13,801)
Changes in cumulative translation adjustment	0	0	0	27,321	0	27,321
Adjustments related to postretirement benefits, net of tax	0	0	0	2,383	0	2,383
Cash dividends	0	0	(2,486)	0	0	(2,486)
Exercise of stock options	101	1,001	0	0	0	1,102
Shares issued under ESPP	243	3,026	0	0	0	3,269
Shares issued for restricted stock units vested	660	(660)	0	0	0	0
Repurchase and retirement of stock	(209)	(2,597)	0	0	0	(2,806)
Share-based compensation expense	0	14,234	0	0	0	14,234
Changes in unrealized gains and losses on investments, net of tax						0
Balance at Dec. 26, 2020	42,190	448,194	26,230	(4,326)	0	512,288
Net income (loss)	0	0	167,325	0	0	167,325
Changes in cumulative translation adjustment	0	0	0	(22,956)	0	(22,956)
Adjustments related to postretirement benefits, net of tax	0	0	0	2,602	0	2,602
Exercise of stock options	250	2,260	0	0	0	2,510
Shares issued under ESPP	161	3,403	0	0	0	3,564
Shares issued for restricted stock units vested	704	(704)	0	0	0	0
Repurchase and retirement of stock	(242)	(10,222)	0	0	0	(10,464)
Share-based compensation expense	0	14,420	0	0	0	14,420
Common stock repurchases	0	0	0	0	(7,324)	(7,324)
Changes in unrealized gains and losses on investments, net of tax	0	0	0	(67)	0	(67)
Impact of sale of PCB Test business	0	0	0	(2,515)	0	(2,515)
Sale of common stock, net of issuance costs	5,693	217,426	0	0	0	223,119
Balance at Dec. 25, 2021	48,756	674,777	193,555	(27,262)	(7,324)	882,502
Net income (loss)	0	0	96,847	0	0	96,847
Changes in cumulative translation adjustment	0	0	0	(17,950)	0	(17,950)
Adjustments related to postretirement benefits, net of tax	0	0	0	5,894	0	5,894
Exercise of stock options	12	105	0	0	0	117
Shares issued under ESPP	161	3,470	0	0	0	3,631
Shares issued for restricted stock units vested	529	(529)	0	0	0	0
Repurchase and retirement of stock	(182)	(5,523)	0	0	0	(5,705)
Share-based compensation expense	0	14,918	0	0	0	14,918
Common stock repurchases	0	0	0	0	(50,719)	(50,719)
Changes in unrealized gains and losses on investments, net of tax	0	0	0	(694)	0	(694)
Balance at Dec. 31, 2022	$ 49,276	$ 687,218	$ 290,402	$ (40,012)	$ (58,043)	$ 928,841