Schedule of Changes in Fair Value of Level 3 Contingent Consideration (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Oct. 04, 2015	Sep. 28, 2014	Oct. 04, 2015	Sep. 28, 2014
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period		$ 35,595	$ 2,230	$ 3,350	$ 2,230
Fair value adjustment	[1],[2]	(1,000)	(630)	(2,600)	(630)
Ending Balance		$ 34,595	$ 1,600	34,595	$ 1,600
Universal Robots
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition				$ 33,845

[1] 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.

[2] 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 in the periods of 2015 and 2016.