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Operating Segments and Enterprise-Wide Information - Revenue by Segment, Recognition Type, and Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 189,964	$ 177,996	$ 564,676	$ 496,573
Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	154,850	150,773	467,389	419,272
Systems
Disaggregation of Revenue [Line Items]
Revenues	35,114	27,223	97,287	77,301
Taiwan
Disaggregation of Revenue [Line Items]
Revenues	41,574	36,935	139,038	101,886
Taiwan | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	34,100	33,351	125,571	93,596
Taiwan | Systems
Disaggregation of Revenue [Line Items]
Revenues	7,474	3,584	13,467	8,290
South Korea
Disaggregation of Revenue [Line Items]
Revenues	28,972	29,571	84,234	58,772
South Korea | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	27,895	28,337	81,322	56,278
South Korea | Systems
Disaggregation of Revenue [Line Items]
Revenues	1,077	1,234	2,912	2,494
United States
Disaggregation of Revenue [Line Items]
Revenues	25,468	36,328	87,604	96,365
United States | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	18,530	31,596	64,012	79,575
United States | Systems
Disaggregation of Revenue [Line Items]
Revenues	6,938	4,732	23,592	16,790
China
Disaggregation of Revenue [Line Items]
Revenues	51,047	28,546	125,499	120,946
China | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	46,011	24,851	107,838	107,756
China | Systems
Disaggregation of Revenue [Line Items]
Revenues	5,036	3,695	17,661	13,190
Asia-Pacific
Disaggregation of Revenue [Line Items]
Revenues	19,881	8,954	63,127	23,317
Asia-Pacific | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	18,566	5,505	59,013	14,307
Asia-Pacific | Systems
Disaggregation of Revenue [Line Items]
Revenues	1,315	3,449	4,114	9,010
Europe
Disaggregation of Revenue [Line Items]
Revenues	10,486	16,979	32,495	52,154
Europe | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	3,595	11,679	12,894	36,656
Europe | Systems
Disaggregation of Revenue [Line Items]
Revenues	6,891	5,300	19,601	15,498
Japan
Disaggregation of Revenue [Line Items]
Revenues	10,728	17,145	27,753	35,574
Japan | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	5,767	12,288	14,493	24,502
Japan | Systems
Disaggregation of Revenue [Line Items]
Revenues	4,961	4,857	13,260	11,072
Rest of the world
Disaggregation of Revenue [Line Items]
Revenues	1,808	3,538	4,926	7,559
Rest of the world | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	386	3,166	2,246	6,602
Rest of the world | Systems
Disaggregation of Revenue [Line Items]
Revenues	1,422	372	2,680	957
Products transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenues	187,781	176,239	554,941	490,922
Products transferred at a point in time | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	154,217	150,252	465,822	417,529
Products transferred at a point in time | Systems
Disaggregation of Revenue [Line Items]
Revenues	33,564	25,987	89,119	73,393
Products and services transferred over time
Disaggregation of Revenue [Line Items]
Revenues	2,183	1,757	9,735	5,651
Products and services transferred over time | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	633	521	1,567	1,743
Products and services transferred over time | Systems
Disaggregation of Revenue [Line Items]
Revenues	1,550	1,236	8,168	3,908
Foundry & Logic
Disaggregation of Revenue [Line Items]
Revenues	104,640	108,411	321,776	323,503
Foundry & Logic | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	104,640	108,411	321,776	323,503
Foundry & Logic | Systems
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
DRAM
Disaggregation of Revenue [Line Items]
Revenues	39,816	31,379	115,802	75,127
DRAM | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	39,816	31,379	115,802	75,127
DRAM | Systems
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Flash
Disaggregation of Revenue [Line Items]
Revenues	10,394	10,983	29,811	20,642
Flash | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	10,394	10,983	29,811	20,642
Flash | Systems
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Systems
Disaggregation of Revenue [Line Items]
Revenues	35,114	27,223	97,287	77,301
Systems | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Systems | Systems
Disaggregation of Revenue [Line Items]
Revenues	$ 35,114	$ 27,223	$ 97,287	$ 77,301

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