Disaggregated Revenue by Primary Geographical Market, Major Product Line and Timing of Revenue Recognition (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2018	Jul. 02, 2017	Jul. 01, 2018	Jul. 02, 2017
Disaggregation of Revenue [Line Items]
Total	$ 526,929	$ 696,901	$ 1,014,396	$ 1,153,814
Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	360,088	593,152	733,416	948,679
System Test
Disaggregation of Revenue [Line Items]
Total	69,682	36,732	112,702	76,578
Industrial Automation
Disaggregation of Revenue [Line Items]
Total	62,057	39,337	110,891	75,610
Wireless Test
Disaggregation of Revenue [Line Items]
Total	35,212	$ 27,680	57,719	$ 52,947
Corporate and Other
Disaggregation of Revenue [Line Items]
Total	(110)		(332)
Americas | Point in time
Disaggregation of Revenue [Line Items]
Total	53,486		98,480
Americas | Point in time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	4,716		9,695
Americas | Point in time | Corporate and Other
Disaggregation of Revenue [Line Items]
Total	(110)		(332)
Americas | Over time
Disaggregation of Revenue [Line Items]
Total	17,125		33,785
Americas | Over time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	122		233
Europe, Middle East and Africa | Point in time
Disaggregation of Revenue [Line Items]
Total	45,012		86,423
Europe, Middle East and Africa | Point in time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	26		1,066
Europe, Middle East and Africa | Over time
Disaggregation of Revenue [Line Items]
Total	8,978		16,925
Europe, Middle East and Africa | Over time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	257		484
Asia Pacific
Disaggregation of Revenue [Line Items]
Total	3,625		7,894
Asia Pacific | Wireless Test
Disaggregation of Revenue [Line Items]
Total	325		513
Asia Pacific | Point in time
Disaggregation of Revenue [Line Items]
Total	356,803		688,600
Asia Pacific | Point in time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	27,663		41,329
Asia Pacific | Over time
Disaggregation of Revenue [Line Items]
Total	41,900		82,289
Asia Pacific | Over time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	2,103		4,399
SOC | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	293,532		594,299
SOC | Americas | Point in time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	12,111		21,711
SOC | Americas | Over time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	8,934		17,517
SOC | Europe, Middle East and Africa | Point in time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	10,227		22,352
SOC | Europe, Middle East and Africa | Over time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	5,689		10,888
SOC | Asia Pacific | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	3,268		7,115
SOC | Asia Pacific | Point in time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	218,352		446,543
SOC | Asia Pacific | Over time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	34,951		68,173
Memory | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	66,556		139,117
Memory | Americas | Point in time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	2,827		5,691
Memory | Americas | Over time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	710		1,406
Memory | Europe, Middle East and Africa | Point in time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	847		986
Memory | Europe, Middle East and Africa | Over time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	254		523
Memory | Asia Pacific | Point in time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	59,633		125,904
Memory | Asia Pacific | Over time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	2,285		4,607
Defense/Aerospace | System Test
Disaggregation of Revenue [Line Items]
Total	23,122		43,264
Defense/Aerospace | Americas | Point in time | System Test
Disaggregation of Revenue [Line Items]
Total	15,256		26,853
Defense/Aerospace | Americas | Over time | System Test
Disaggregation of Revenue [Line Items]
Total	6,237		12,425
Defense/Aerospace | Europe, Middle East and Africa | Point in time | System Test
Disaggregation of Revenue [Line Items]
Total	447		1,943
Defense/Aerospace | Europe, Middle East and Africa | Over time | System Test
Disaggregation of Revenue [Line Items]
Total	539		1,090
Defense/Aerospace | Asia Pacific | Point in time | System Test
Disaggregation of Revenue [Line Items]
Total	385		487
Defense/Aerospace | Asia Pacific | Over time | System Test
Disaggregation of Revenue [Line Items]
Total	258		466
Storage Test | System Test
Disaggregation of Revenue [Line Items]
Total	33,257		45,191
Storage Test | Americas | Point in time | System Test
Disaggregation of Revenue [Line Items]
Total	5		284
Storage Test | Asia Pacific | Point in time | System Test
Disaggregation of Revenue [Line Items]
Total	31,824		41,946
Storage Test | Asia Pacific | Over time | System Test
Disaggregation of Revenue [Line Items]
Total	1,428		2,961
Production Board Test | System Test
Disaggregation of Revenue [Line Items]
Total	13,303		24,247
Production Board Test | Americas | Point in time | System Test
Disaggregation of Revenue [Line Items]
Total	1,429		3,189
Production Board Test | Americas | Over time | System Test
Disaggregation of Revenue [Line Items]
Total	795		1,552
Production Board Test | Europe, Middle East and Africa | Point in time | System Test
Disaggregation of Revenue [Line Items]
Total	4,849		8,886
Production Board Test | Europe, Middle East and Africa | Over time | System Test
Disaggregation of Revenue [Line Items]
Total	1,713		3,272
Production Board Test | Asia Pacific | System Test
Disaggregation of Revenue [Line Items]
Total	32		266
Production Board Test | Asia Pacific | Point in time | System Test
Disaggregation of Revenue [Line Items]
Total	3,741		5,603
Production Board Test | Asia Pacific | Over time | System Test
Disaggregation of Revenue [Line Items]
Total	744		1,479
Universal Robots (UR) | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	57,548		106,382
Universal Robots (UR) | Americas | Point in time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	16,053		30,190
Universal Robots (UR) | Americas | Over time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	327		652
Universal Robots (UR) | Europe, Middle East and Africa | Point in time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	26,616		49,190
Universal Robots (UR) | Europe, Middle East and Africa | Over time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	526		668
Universal Robots (UR) | Asia Pacific | Point in time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	13,895		25,478
Universal Robots (UR) | Asia Pacific | Over time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	131		204
Mobile Industrial Robots (MiR) | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	4,509		4,509
Mobile Industrial Robots (MiR) | Americas | Point in time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	1,199		1,199
Mobile Industrial Robots (MiR) | Europe, Middle East and Africa | Point in time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	2,000		2,000
Mobile Industrial Robots (MiR) | Asia Pacific | Point in time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	$ 1,310		$ 1,310