Schedule of Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jul. 01, 2018		Jul. 02, 2017		Jul. 01, 2018		Jul. 02, 2017		Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues		$ 526,929		$ 696,901		$ 1,014,396		$ 1,153,814
Income (loss) before income taxes	[1],[2]	120,012		206,877		215,831		298,893
Total assets		2,931,720	[3]	3,030,225	[3]	2,931,720	[3]	3,030,225	[3]	$ 3,109,545
Semiconductor Test
Segment Reporting Information [Line Items]
Revenues		360,088		593,152		733,416		948,679
Income (loss) before income taxes	[1],[2]	91,159		211,278		179,238		309,244
Total assets	[3]	765,484		766,395		765,484		766,395
System Test
Segment Reporting Information [Line Items]
Revenues		69,682		36,732		112,702		76,578
Income (loss) before income taxes	[1],[2]	20,352		(5,692)		26,240		(8,451)
Total assets	[3]	107,199		108,083		107,199		108,083
Industrial Automation
Segment Reporting Information [Line Items]
Revenues		62,057		39,337		110,891		75,610
Income (loss) before income taxes	[1],[2]	(2,922)		(1,081)		(2,138)		(3,652)
Total assets	[3]	597,293		349,023		597,293		349,023
Wireless Test
Segment Reporting Information [Line Items]
Revenues		35,212		27,680		57,719		52,947
Income (loss) before income taxes	[1],[2]	10,308		4,514		10,772		6,046
Total assets	[3]	77,638		62,900		77,638		62,900
Corporate and Eliminations
Segment Reporting Information [Line Items]
Revenues		(110)				(332)
Income (loss) before income taxes	[1],[2]	1,115		(2,142)		1,719		(4,294)
Total assets	[3]	$ 1,384,106		$ 1,743,824		$ 1,384,106		$ 1,743,824

[1] Included in Corporate and Other are: contingent consideration adjustments, severance charges, interest income, interest expense, net foreign exchange gains (losses), and acquisition related charges.

[2] Included in the income (loss) before income taxes for each of the segments are charges and credits related to restructuring and other and inventory charges.

[3] Total business assets are directly attributable to each business. Corporate assets consist of cash and cash equivalents, marketable securities and certain other assets.