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. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total	$ 582,038	$ 566,848	$ 1,640,315	$ 1,581,244
Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	397,737	417,297	1,113,489	1,150,712
System Test
Disaggregation of Revenue [Line Items]
Total	73,305	49,606	204,934	162,308
Industrial Automation
Disaggregation of Revenue [Line Items]
Total	68,892	65,913	209,753	176,803
Wireless Test
Disaggregation of Revenue [Line Items]
Total	42,264	34,304	112,541	92,023
Corporate and Other
Disaggregation of Revenue [Line Items]
Total	(160)	(272)	(402)	(602)
Americas | Point in Time
Disaggregation of Revenue [Line Items]
Total	61,604	54,810	180,802	153,293
Americas | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	5,621	3,820	12,961	13,515
Americas | Point in Time | Corporate and Other
Disaggregation of Revenue [Line Items]
Total	(160)	(272)	(402)	(602)
Americas | Over Time
Disaggregation of Revenue [Line Items]
Total	16,932	16,825	51,929	50,820
Americas | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	723	146	1,550	379
Europe, Middle East and Africa | Point in Time
Disaggregation of Revenue [Line Items]
Total	44,052	45,788	138,225	132,206
Europe, Middle East and Africa | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	1,220	1,504	2,575	2,570
Europe, Middle East and Africa | Over Time
Disaggregation of Revenue [Line Items]
Total	8,648	8,709	25,519	25,650
Europe, Middle East and Africa | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	48	318	140	802
Asia Pacific
Disaggregation of Revenue [Line Items]
Total	1,453	2,290	4,852	10,183
Asia Pacific | Wireless Test
Disaggregation of Revenue [Line Items]
Total	75	171	140	684
Asia Pacific | Point in Time
Disaggregation of Revenue [Line Items]
Total	403,345	393,979	1,100,453	1,079,239
Asia Pacific | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	33,032	26,851	91,029	68,180
Asia Pacific | Over Time
Disaggregation of Revenue [Line Items]
Total	46,004	44,447	138,535	129,853
Asia Pacific | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	1,545	1,494	4,146	5,893
SOC | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	325,766	330,407	934,987	924,702
SOC | Americas | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	6,307	8,866	21,830	30,577
SOC | Americas | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	8,497	8,810	24,862	26,536
SOC | Europe, Middle East and Africa | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	6,894	9,728	27,934	32,079
SOC | Europe, Middle East and Africa | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	5,189	5,336	15,681	16,240
SOC | Asia Pacific | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	1,290	2,047	4,487	9,162
SOC | Asia Pacific | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	259,909	258,898	727,035	702,097
SOC | Asia Pacific | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	37,680	36,722	113,158	108,011
Memory | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	71,971	86,890	178,502	226,010
Memory | Americas | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	3,464	4,600	19,574	10,291
Memory | Americas | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	621	686	2,056	2,092
Memory | Europe, Middle East and Africa | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	274	2,080	2,443	3,066
Memory | Europe, Middle East and Africa | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	255	301	819	824
Memory | Asia Pacific | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	63,483	76,429	143,163	202,336
Memory | Asia Pacific | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	3,874	2,794	10,447	7,401
Defense/Aerospace | System Test
Disaggregation of Revenue [Line Items]
Total	30,284	23,269	78,336	66,533
Defense/Aerospace | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	22,861	15,423	54,870	42,276
Defense/Aerospace | Americas | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	5,814	6,037	19,116	18,462
Defense/Aerospace | Europe, Middle East and Africa | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	742	161	992	2,104
Defense/Aerospace | Europe, Middle East and Africa | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	469	505	1,442	1,596
Defense/Aerospace | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	99	931	525	1,417
Defense/Aerospace | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	299	212	1,391	678
Storage Test | System Test
Disaggregation of Revenue [Line Items]
Total	26,424	12,032	80,362	57,224
Storage Test | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	2,232	0	7,528	284
Storage Test | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	22,696	9,916	66,974	51,863
Storage Test | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	1,496	2,116	5,860	5,077
Production Board Test | System Test
Disaggregation of Revenue [Line Items]
Total	16,597	14,305	46,236	38,551
Production Board Test | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	2,165	2,625	6,760	5,814
Production Board Test | Americas | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	796	789	2,317	2,342
Production Board Test | Europe, Middle East and Africa | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	4,354	3,223	12,391	12,109
Production Board Test | Europe, Middle East and Africa | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	1,613	1,510	4,782	4,781
Production Board Test | Asia Pacific | System Test
Disaggregation of Revenue [Line Items]
Total	88	72	225	337
Production Board Test | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	6,751	5,201	17,235	10,804
Production Board Test | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	830	885	2,526	2,364
Universal Robots (UR) | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	58,458	58,552	177,673	164,247
Universal Robots (UR) | Americas | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	16,294	17,834	48,529	48,025
Universal Robots (UR) | Americas | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	293	190	793	431
Universal Robots (UR) | Europe, Middle East and Africa | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	25,557	26,445	78,007	75,631
Universal Robots (UR) | Europe, Middle East and Africa | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	459	282	1,274	675
Universal Robots (UR) | Asia Pacific | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	15,575	13,656	48,284	39,135
Universal Robots (UR) | Asia Pacific | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	280	145	786	350
MiR | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	9,631	6,544	29,243	11,053
MiR | Americas | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	2,820	1,810	9,152	3,009
MiR | Europe, Middle East and Africa | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	5,011	2,647	13,883	4,647
MiR | Asia Pacific | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	1,800	2,087	6,208	3,397
Energid Technologies Corporation | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	803	817	2,837	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	188	167	1,235	578
Energid Technologies Corporation | Europe, Middle East and Africa | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	$ 615	457	1,381	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	$ 221	$ 79