Schedule of Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended				9 Months Ended
		Oct. 04, 2015		Sep. 28, 2014		Oct. 04, 2015		Sep. 28, 2014		Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues		$ 465,994		$ 478,010		$ 1,321,133		$ 1,324,587
Income (loss) before income taxes	[1],[2]	87,408		100,670		261,981		220,189
Total assets		2,661,884	[3]	2,695,007	[3]	2,661,884	[3]	2,695,007	[3]	$ 2,538,520
Semiconductor Test
Segment Reporting Information [Line Items]
Revenues		325,516		380,083		996,748		1,063,254
Income (loss) before income taxes	[1],[2]	73,957		91,900		246,627		233,770
Total assets	[3]	591,445		748,499		591,445		748,499
Wireless Test
Segment Reporting Information [Line Items]
Revenues		55,359		54,838		152,285		144,747
Income (loss) before income taxes	[1],[2]	2,997		2,379		(603)		(8,477)
Total assets	[3]	447,461		614,911		447,461		614,911
System Test
Segment Reporting Information [Line Items]
Revenues		69,062		43,089		152,320		116,586
Income (loss) before income taxes	[1],[2]	13,751		5,779		10,423		5,512
Total assets	[3]	109,078		83,769		109,078		83,769
Corporate And Eliminations
Segment Reporting Information [Line Items]
Income (loss) before income taxes	[1],[2]	1,550		612		12,081		(10,616)
Total assets	[3]	1,153,832		$ 1,247,828		1,153,832		$ 1,247,828
Industrial Automation
Segment Reporting Information [Line Items]
Revenues		16,057				19,780
Income (loss) before income taxes	[1],[2]	(4,847)				(6,547)
Total assets	[3]	$ 360,068				$ 360,068

[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.