Disaggregated Revenue by Primary Geographical Market, Major Product Line and Timing of Revenue Recognition (Detail) - USD ($) $ in Thousands		3 Months Ended
		Apr. 01, 2018	Apr. 02, 2017
Disaggregation of Revenue [Line Items]
Total		$ 487,467	$ 456,913
Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		373,328	355,528
System Test
Disaggregation of Revenue [Line Items]
Total		43,019	39,845
Industrial Automation
Disaggregation of Revenue [Line Items]
Total		48,834	36,272
Wireless Test
Disaggregation of Revenue [Line Items]
Total		22,507	$ 25,268
Corporate and Other
Disaggregation of Revenue [Line Items]
Total		(221)
Americas | Point in Time
Disaggregation of Revenue [Line Items]
Total		45,229
Americas | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		14,373
Americas | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total		4,979
Americas | Point in Time | Corporate and Other
Disaggregation of Revenue [Line Items]
Total		(221)
Americas | Over Time
Disaggregation of Revenue [Line Items]
Total		16,633
Americas | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		89
Americas | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total		112
Europe, Middle East and Africa | Point in Time
Disaggregation of Revenue [Line Items]
Total		41,412
Europe, Middle East and Africa | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		22,573
Europe, Middle East and Africa | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total		1,041
Europe, Middle East and Africa | Over Time
Disaggregation of Revenue [Line Items]
Total		7,963
Europe, Middle East and Africa | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		143
Europe, Middle East and Africa | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total		227
Asia Pacific
Disaggregation of Revenue [Line Items]
Total		4,269
Asia Pacific | Wireless Test
Disaggregation of Revenue [Line Items]
Total		188
Asia Pacific | Point in Time
Disaggregation of Revenue [Line Items]
Total		328,455
Asia Pacific | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		11,583
Asia Pacific | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total		13,664
Asia Pacific | Over Time
Disaggregation of Revenue [Line Items]
Total		43,506
Asia Pacific | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total		73
Asia Pacific | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total		2,296
SOC | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	[1]	300,766
SOC | Americas | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	[1]	9,600
SOC | Americas | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	[1]	8,791
SOC | Europe, Middle East and Africa | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	[1]	12,125
SOC | Europe, Middle East and Africa | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	[1]	5,214
SOC | Asia Pacific | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	[1]	3,847
SOC | Asia Pacific | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	[1]	224,851
SOC | Asia Pacific | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	[1]	36,338
Memory | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		72,562
Memory | Americas | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		2,862
Memory | Americas | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		696
Memory | Europe, Middle East and Africa | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		139
Memory | Europe, Middle East and Africa | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		269
Memory | Asia Pacific | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		66,273
Memory | Asia Pacific | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total		2,323
Defense/Aerospace | System Test
Disaggregation of Revenue [Line Items]
Total		20,142
Defense/Aerospace | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		11,597
Defense/Aerospace | Americas | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total		6,188
Defense/Aerospace | Europe, Middle East and Africa | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		1,497
Defense/Aerospace | Europe, Middle East and Africa | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total		551
Defense/Aerospace | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		101
Defense/Aerospace | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total		208
Storage Test | System Test
Disaggregation of Revenue [Line Items]
Total		11,934
Storage Test | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		279
Storage Test | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		10,122
Storage Test | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total		1,533
Production Board Test | System Test
Disaggregation of Revenue [Line Items]
Total		10,943
Production Board Test | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		1,760
Production Board Test | Americas | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total		757
Production Board Test | Europe, Middle East and Africa | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		4,037
Production Board Test | Europe, Middle East and Africa | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total		1,559
Production Board Test | Asia Pacific | System Test
Disaggregation of Revenue [Line Items]
Total		234
Production Board Test | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total		1,861
Production Board Test | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total		$ 735

[1] System on a chip ("SOC")