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Changes in Carrying Amount of Goodwill by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jul. 03, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Apr. 25, 2018	Feb. 26, 2018
Goodwill [Line Items]
Foreign currency translation adjustment		$ (20,531)	$ 28,668
Goodwill impairment losses			(254,946)
Goodwill		1,014,577	985,909	$ 1,144,416
Accumulated impairment losses		(762,566)	(762,566)	(762,566)
Goodwill		252,011	223,343	381,850
Mobile Industrial Robots (MiR)
Goodwill [Line Items]
Goodwill acquisition		135,976
Goodwill					$ 135,976
Energid Technologies Corporation
Goodwill [Line Items]
Goodwill acquisition		14,394
Goodwill						$ 14,400
Industrial Automation
Goodwill [Line Items]
Foreign currency translation adjustment		(20,531)	28,668
Goodwill		233,519	204,851	363,358
Goodwill		233,519	204,851	363,358
Industrial Automation \| Mobile Industrial Robots (MiR)
Goodwill [Line Items]
Goodwill acquisition		135,976
Industrial Automation \| Energid Technologies Corporation
Goodwill [Line Items]
Goodwill acquisition		14,394
Wireless Test
Goodwill [Line Items]
Goodwill impairment losses	$ (254,900)		(254,946)
Goodwill		361,819	361,819	361,819
Accumulated impairment losses		(353,843)	(353,843)	(353,843)
Goodwill	$ 8,000	7,976	7,976	7,976
Semiconductor Test
Goodwill [Line Items]
Goodwill		260,540	260,540	260,540
Accumulated impairment losses		(260,540)	(260,540)	(260,540)
Goodwill		0	0	0
System Test
Goodwill [Line Items]
Goodwill		158,699	158,699	158,699
Accumulated impairment losses		(148,183)	(148,183)	(148,183)
Goodwill		$ 10,516	$ 10,516	$ 10,516