Schedule of Changes in Fair Value of Level 3 Contingent Consideration (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Oct. 02, 2016	Oct. 04, 2015	Oct. 02, 2016	Oct. 04, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period		$ 24,914	$ 35,595	$ 37,436	$ 3,350
Payments	[1]			(15,000)
Fair value adjustment	[2],[3],[4],[5]	7,973	(1,000)	10,451	(2,600)
Ending Balance		$ 32,887	$ 34,595	$ 32,887	34,595
Universal Robots
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition					$ 33,845

[1] In the nine months ended October 2, 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 nine months ended October 2, 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 nine months ended October 4, 2015, the fair value measurement of the contingent consideration for the earn-out in connection with the acquisition of ZTEC Instruments, Inc. was reduced by $1.6 million, 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.

[4] In the three and nine months ended October 2, 2016, the fair value of contingent consideration for the earn-out in connection with the acquisition of Universal Robots was increased by $8.0 million and $9.9 million, respectively, primarily due to an increase in forecasted revenue and a decrease in the discount rate.

[5] In the three and nine months ended October 4, 2015, the fair value of contingent consideration for the earn-out in connection with the acquisition of AIT was reduced by $1.0 million due to a decrease in the revenue probabilities.