Schedule of Changes in Fair Value of Level 3 Contingent Consideration (Detail) - USD ($) $ in Thousands		3 Months Ended
		Apr. 03, 2016	Apr. 05, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period		$ 37,436	$ 3,350
Payments	[1]	(15,000)	0
Fair value adjustment	[2]	1,173	0
Ending Balance		$ 23,609	$ 3,350

[1] In the three months ended April 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 months ended April 3, 2016, the fair value of contingent consideration for the earn-out in connection with the acquisition of Universal Robots was increased by $1.2 million primarily due to a lower discount rate.