Schedule of Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jul. 05, 2015		Jun. 29, 2014		Jul. 05, 2015		Jun. 29, 2014		Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues		$ 512,739		$ 525,567		$ 855,140		$ 846,577
Income (loss) before income taxes	[1],[2]	132,136		121,392		174,574		119,519
Total assets		2,692,807	[3]	2,630,663	[3]	2,692,807	[3]	2,630,663	[3]	$ 2,538,520
Semiconductor Test
Segment Reporting Information [Line Items]
Revenues		400,315		421,434		671,232		683,171
Income (loss) before income taxes	[1],[2]	129,546		107,270		172,671		141,870
Total assets	[3]	649,087		747,492		649,087		747,492
Wireless Test
Segment Reporting Information [Line Items]
Revenues		62,879		68,699		96,927		89,909
Income (loss) before income taxes	[1],[2]	6,841		14,229		(3,600)		(10,856)
Total assets	[3]	485,857		638,012		485,857		638,012
System Test
Segment Reporting Information [Line Items]
Revenues		45,822		35,434		83,258		73,497
Income (loss) before income taxes	[1],[2]	(4,333)		(715)		(3,328)		(267)
Total assets	[3]	95,544		71,644		95,544		71,644
Corporate And Eliminations
Segment Reporting Information [Line Items]
Income (loss) before income taxes	[1],[2]	1,782		608		10,531		(11,228)
Total assets	[3]	1,104,043		$ 1,173,515		1,104,043		$ 1,173,515
Industrial Automation
Segment Reporting Information [Line Items]
Revenues		3,723				3,723
Income (loss) before income taxes	[1],[2]	(1,700)				(1,700)
Total assets	[3]	$ 358,276				$ 358,276

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

[2] Interest income, interest expense, and other (income) expense, net are included in Corporate and Eliminations.

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