Schedule of Changes in Fair Value of Level 3 Contingent Consideration (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jul. 03, 2016	Jul. 05, 2015	Jul. 03, 2016	Jul. 05, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period		$ 23,609	$ 3,350	$ 37,436	$ 3,350
Payments	[1]			(15,000)
Fair value adjustment	[2],[3],[4]	1,305	(1,600)	2,478	(1,600)
Ending Balance		$ 24,914	35,595	$ 24,914	35,595
Universal Robots
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition			$ 33,845		$ 33,845

[1] In the six months ended July 3, 2016, based on Universal Robots' calendar year 2015 EBITDA results, Teradyne paid $15 million or 100% of the eligible EBITDA contingent consideration amount.

[2] 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 Avionics Interface Technology, LLC ("AIT") was increased by $0.6 million due to an increase in forecasted revenue.

[3] 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.

[4] In the three and six months ended July 5, 2015, the fair value measurement of the contingent consideration for the earn-out in connection with the acquisition of ZTEC Instruments, Inc. ("ZTEC") was reduced to $0 because Teradyne and the Securityholder Representative, on behalf of the ZTEC securityholders, agreed to terminate the earn-out prior to the end of the December 31, 2015 earn-out period, with no payout in connection with the resolution of indemnity claims asserted by both Teradyne and the Securityholder Representative.