Schedule of Changes in Fair Value of Level 3 Contingent Consideration (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period		$ 70,543	$ 45,102
Acquisition of MiR		23,976	52,547
Foreign currency impact		(967)	(3,540)
Payments	[1]	(34,590)	(24,553)
Fair value adjustment	[2]	(19,257)	987
Balance at end of period		$ 39,705	$ 70,543

[1] During the year ended December 31, 2018, Teradyne paid $24.6 million of contingent consideration for the earn-out in connection with the acquisition of Universal Robots.

[2] During the year ended December 31, 2018, the fair value of contingent consideration for the earn-out in connection with the acquisition of MiR was increased by $17.7 million primarily due to an increase in forecasted revenues. During the year ended December 31, 2018, the fair value of contingent consideration for the earn-out in connection with the acquisition of Universal Robots was decreased by $16.7 million primarily due to a decrease in forecasted revenues.