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	122,703	0	0	122,703
Changes in cumulative translation adjustment	0	0	0	(7,356)	0	(7,356)
Adjustments related to postretirement benefits	0	0	0	(29)	0	(29)
Changes in unrealized gains and losses on investments, net of tax	0	0	0	(14)	0	(14)
Exercise of stock options	214	1,945	0	0	0	2,159
Shares issued under ESPP	95	1,654	0	0	0	1,749
Shares issued for restricted stock units vested	620	(620)	0	0	0	0
Repurchase and retirement of stock	(216)	(9,314)	0	0	0	(9,530)
Share-based compensation expense	0	7,657	0	0	0	7,657
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 Jun. 26, 2021	48,596	666,942	148,933	(14,240)	0	850,231
Balance at Mar. 27, 2021	48,411	661,984	53,837	(14,758)	0	749,474
Net income	0	0	95,096	0	0	95,096
Changes in cumulative translation adjustment	0	0	0	2,890	0	2,890
Adjustments related to postretirement benefits	0	0	0	151	0	151
Changes in unrealized gains and losses on investments, net of tax	0	0	0	(8)	0	(8)
Exercise of stock options	22	215	0	0	0	237
Shares issued under ESPP	95	1,654	0	0	0	1,749
Shares issued for restricted stock units vested	94	(94)	0	0	0	0
Repurchase and retirement of stock	(26)	(951)	0	0	0	(977)
Share-based compensation expense	0	4,134	0	0	0	4,134
Impact of sale of PCB Test business	0	0	0	(2,515)	0	(2,515)
Balance at Jun. 26, 2021	48,596	666,942	148,933	(14,240)	0	850,231
Balance at Dec. 25, 2021	48,756	674,777	193,555	(27,262)	(7,324)	882,502	[1]
Net income	0	0	50,337	0	0	50,337
Changes in cumulative translation adjustment	0	0	0	(21,440)	0	(21,440)
Adjustments related to postretirement benefits	0	0	0	(173)	0	(173)
Changes in unrealized gains and losses on investments, net of tax	0	0	0	(510)	0	(510)
Exercise of stock options	13	105	0	0	0	118
Shares issued under ESPP	77	1,669	0	0	0	1,746
Shares issued for restricted stock units vested	466	(466)	0	0	0	0
Repurchase and retirement of stock	(160)	(4,945)	0	0	0	(5,105)
Common stock repurchases	0	0	0	0	(20,378)	(20,378)
Share-based compensation expense	0	7,355	0	0	0	7,355
Balance at Jun. 25, 2022	49,152	678,495	243,892	(49,385)	(27,702)	894,452
Balance at Mar. 26, 2022	49,025	673,034	215,124	(36,574)	(13,712)	886,897
Net income	0	0	28,768	0	0	28,768
Changes in cumulative translation adjustment	0	0	0	(12,537)	0	(12,537)
Adjustments related to postretirement benefits	0	0	0	(112)	0	(112)
Changes in unrealized gains and losses on investments, net of tax	0	0	0	(162)	0	(162)
Exercise of stock options	13	105	0	0	0	118
Shares issued under ESPP	77	1,669	0	0	0	1,746
Shares issued for restricted stock units vested	40	(40)	0	0	0	0
Repurchase and retirement of stock	(3)	(206)	0	0	0	(209)
Common stock repurchases	0	0	0	0	(13,990)	(13,990)
Share-based compensation expense	0	3,933	0	0	0	3,933
Balance at Jun. 25, 2022	$ 49,152	$ 678,495	$ 243,892	$ (49,385)	$ (27,702)	$ 894,452

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