Schedule of Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended
		Apr. 03, 2016		Apr. 05, 2015		Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues		$ 430,994		$ 342,401
Income (loss) before income taxes	[1],[2]	57,192		42,438
Total assets		2,548,974	[3]	2,512,182	[3]	$ 2,548,674
Semiconductor Test
Segment Reporting Information [Line Items]
Revenues		340,264		270,917
Income (loss) before income taxes	[1],[2]	73,254		43,125
Total assets	[3]	664,555		596,477
Wireless Test
Segment Reporting Information [Line Items]
Revenues		20,314		34,048
Income (loss) before income taxes	[1],[2]	(20,140)		(10,441)
Total assets	[3]	408,466		465,465
System Test
Segment Reporting Information [Line Items]
Revenues		53,670		37,436
Income (loss) before income taxes	[1],[2]	9,492		1,005
Total assets	[3]	90,695		94,133
Corporate And Eliminations
Segment Reporting Information [Line Items]
Income (loss) before income taxes	[1],[2]	1,754		8,749
Total assets	[3]	1,034,669		$ 1,356,107
Industrial Automation
Segment Reporting Information [Line Items]
Revenues		16,746
Income (loss) before income taxes	[1],[2]	(7,168)
Total assets	[3]	$ 350,589

[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.