Schedule of Changes in Fair Value of Level 3 Contingent Consideration (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jul. 02, 2017	Jul. 03, 2016	Jul. 02, 2017	Jul. 03, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period		$ 37,916	$ 23,609	$ 38,332	$ 37,436
Payments	[1]			(1,050)	(15,000)
Fair value adjustment	[2],[3]	1,499	1,305	2,133	2,478
Ending Balance		$ 39,415	$ 24,914	$ 39,415	$ 24,914

[1] In the six months ended July 2, 2017, Teradyne paid $1.1 million of contingent consideration for the earn-out in connection with the acquisition of Avionics Interface Technology, LLC ("AIT"). In the six months ended July 3, 2016, based on Universal Robot's calendar year 2015 EBITA results, Teradyne paid $15.0 million or 100% of the eligible EBITA contingent consideration amount in connection with the acquisition of Universal Robots.

[2] In the three and six months ended July 3, 2016, the fair value of contingent consideration for the earn-out in connection with acquisition of AIT was increased by $0.6 million due to an increase in forecasted revenue.

[3] In the three and six months ended July, 2, 2017, the fair value of contingent consideration for the earn-out in connection with the acquisition of Universal Robots was increased by $1.5 million and $2.1 million, respectively, primarily due to a decrease in the discount rate. In the three and six months ended July 3, 2016, the fair value of contingent consideration for the earn-out in connection with the acquisition of Universal Robots was increased by $0.8 million and $1.9 million, respectively, primarily due to a decrease in the discount rate.