Disaggregated Revenue by Primary Geographical Market, Major Product Line and Timing of Revenue Recognition (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Disaggregation of Revenue [Line Items]
Total	$ 566,848	$ 503,378	$ 1,581,244	$ 1,657,191
Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	417,297	396,881	1,150,712	1,345,560
System Test
Disaggregation of Revenue [Line Items]
Total	65,913	40,063	176,803	115,672
Industrial Automation
Disaggregation of Revenue [Line Items]
Total	49,606	35,569	162,308	112,147
Wireless Test
Disaggregation of Revenue [Line Items]
Total	34,304	$ 30,865	92,023	$ 83,812
Corporate and Other
Disaggregation of Revenue [Line Items]
Total	(272)		(602)
Americas | Point in Time
Disaggregation of Revenue [Line Items]
Total	54,810		153,293
Americas | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	3,820		13,515
Americas | Point in Time | Corporate and Other
Disaggregation of Revenue [Line Items]
Total	(272)		(602)
Americas | Over Time
Disaggregation of Revenue [Line Items]
Total	16,825		50,820
Americas | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	146		379
Europe, Middle East and Africa | Point in Time
Disaggregation of Revenue [Line Items]
Total	45,788		132,206
Europe, Middle East and Africa | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	1,504		2,570
Europe, Middle East and Africa | Over Time
Disaggregation of Revenue [Line Items]
Total	8,709		25,650
Europe, Middle East and Africa | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	318		802
Asia Pacific
Disaggregation of Revenue [Line Items]
Total	2,290		10,183
Asia Pacific | Wireless Test
Disaggregation of Revenue [Line Items]
Total	171		684
Asia Pacific | Point in Time
Disaggregation of Revenue [Line Items]
Total	393,979		1,079,239
Asia Pacific | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	26,851		68,180
Asia Pacific | Over Time
Disaggregation of Revenue [Line Items]
Total	44,447		129,853
Asia Pacific | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	1,494		5,893
SOC | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	330,407		924,702
SOC | Americas | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	8,866		30,577
SOC | Americas | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	8,810		26,536
SOC | Europe, Middle East and Africa | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	9,728		32,079
SOC | Europe, Middle East and Africa | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	5,336		16,240
SOC | Asia Pacific | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	2,047		9,162
SOC | Asia Pacific | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	258,898		702,097
SOC | Asia Pacific | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	36,722		108,011
Memory | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	86,890		226,010
Memory | Americas | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	4,600		10,291
Memory | Americas | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	686		2,092
Memory | Europe, Middle East and Africa | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	2,080		3,066
Memory | Europe, Middle East and Africa | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	301		824
Memory | Asia Pacific | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	76,429		202,336
Memory | Asia Pacific | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	2,794		7,401
Defense/Aerospace | System Test
Disaggregation of Revenue [Line Items]
Total	23,269		66,533
Defense/Aerospace | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	15,423		42,276
Defense/Aerospace | Americas | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	6,037		18,462
Defense/Aerospace | Europe, Middle East and Africa | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	161		2,104
Defense/Aerospace | Europe, Middle East and Africa | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	505		1,596
Defense/Aerospace | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	931		1,417
Defense/Aerospace | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	212		678
Storage Test | System Test
Disaggregation of Revenue [Line Items]
Total	12,032		57,224
Storage Test | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total			284
Storage Test | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	9,916		51,863
Storage Test | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	2,116		5,077
Production Board Test | System Test
Disaggregation of Revenue [Line Items]
Total	14,305		38,551
Production Board Test | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	2,625		5,814
Production Board Test | Americas | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	789		2,342
Production Board Test | Europe, Middle East and Africa | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	3,223		12,109
Production Board Test | Europe, Middle East and Africa | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	1,510		4,781
Production Board Test | Asia Pacific | System Test
Disaggregation of Revenue [Line Items]
Total	72		337
Production Board Test | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	5,201		10,804
Production Board Test | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	885		2,364
Universal Robots (UR) | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	58,552		164,247
Universal Robots (UR) | Americas | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	17,834		48,025
Universal Robots (UR) | Americas | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	190		431
Universal Robots (UR) | Europe, Middle East and Africa | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	26,445		75,631
Universal Robots (UR) | Europe, Middle East and Africa | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	282		675
Universal Robots (UR) | Asia Pacific | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	13,656		39,135
Universal Robots (UR) | Asia Pacific | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	145		350
Mobile Industrial Robots (MiR) | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	6,544		11,053
Mobile Industrial Robots (MiR) | Americas | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	1,810		3,009
Mobile Industrial Robots (MiR) | Europe, Middle East and Africa | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	2,647		4,647
Mobile Industrial Robots (MiR) | Asia Pacific | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	2,087		3,397
Energid Technologies Corporation | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	817		1,503
Energid Technologies Corporation | Americas | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	104		104
Energid Technologies Corporation | Americas | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	167		578
Energid Technologies Corporation | Europe, Middle East and Africa | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	457		732
Energid Technologies Corporation | Asia Pacific | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	10		10
Energid Technologies Corporation | Asia Pacific | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	$ 79		$ 79