Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - 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. 26, 2020	$ 42,190	$ 448,194	$ 26,230	$ (4,326)	$ 0	$ 512,288
Net income	0	0	146,436	0	0	146,436
Changes in cumulative translation adjustment	0	0	0	(12,562)	0	(12,562)
Adjustments related to postretirement benefits	0	0	0	15	0	15
Changes in unrealized gains and losses on investments, net of tax	0	0	0	(25)	0	(25)
Shares issued for restricted stock units vested	696	(696)	0	0	0	0
Repurchase and retirement of stock	(240)	(10,167)	0	0	0	(10,407)
Share-based compensation expense	0	11,371	0	0	0	11,371
Exercise of stock options	250	2,260	0	0	0	2,510
Shares issued under ESPP	95	1,654	0	0	0	1,749
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 Sep. 25, 2021	48,684	670,042	172,666	(19,413)	0	871,979
Balance at Jun. 26, 2021	48,596	666,942	148,933	(14,240)	0	850,231
Net income	0	0	23,733	0	0	23,733
Changes in cumulative translation adjustment	0	0	0	(5,206)	0	(5,206)
Adjustments related to postretirement benefits	0	0	0	44	0	44
Changes in unrealized gains and losses on investments, net of tax	0	0	0	(11)	0	(11)
Shares issued for restricted stock units vested	76	(76)	0	0	0	0
Repurchase and retirement of stock	(24)	(853)	0	0	0	(877)
Share-based compensation expense	0	3,714	0	0	0	3,714
Exercise of stock options	36	315	0	0	0	351
Balance at Sep. 25, 2021	48,684	670,042	172,666	(19,413)	0	871,979
Balance at Dec. 25, 2021	48,756	674,777	193,555	(27,262)	(7,324)	882,502	[1]
Net income	0	0	75,219	0	0	75,219
Changes in cumulative translation adjustment	0	0	0	(43,960)	0	(43,960)
Adjustments related to postretirement benefits	0	0	0	(302)	0	(302)
Changes in unrealized gains and losses on investments, net of tax	0	0	0	(882)	0	(882)
Shares issued for restricted stock units vested	521	(521)	0	0	0	0
Repurchase and retirement of stock	(180)	(5,467)	0	0	0	(5,647)
Common stock repurchases	0	0	0	0	(38,078)	(38,078)
Share-based compensation expense	0	11,095	0	0	0	11,095
Exercise of stock options	13	105	0	0	0	118
Shares issued under ESPP	77	1,669	0	0	0	1,746
Balance at Sep. 24, 2022	49,187	681,658	268,774	(72,406)	(45,402)	881,811
Balance at Jun. 25, 2022	49,152	678,495	243,892	(49,385)	(27,702)	894,452
Net income	0	0	24,882	0	0	24,882
Changes in cumulative translation adjustment	0	0	0	(22,520)	0	(22,520)
Adjustments related to postretirement benefits	0	0	0	(129)	0	(129)
Changes in unrealized gains and losses on investments, net of tax	0	0	0	(372)	0	(372)
Shares issued for restricted stock units vested	55	(55)	0	0	0	0
Repurchase and retirement of stock	(20)	(522)	0	0	0	(542)
Common stock repurchases	0	0	0	0	(17,700)	(17,700)
Share-based compensation expense	0	3,740	0	0	0	3,740
Balance at Sep. 24, 2022	$ 49,187	$ 681,658	$ 268,774	$ (72,406)	$ (45,402)	$ 881,811

[1] Derived from December 25, 2021 audited financial statements