Schedule of Changes in Fair Value of Level 3 Contingent Consideration (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021		Dec. 31, 2020
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period		$ 7,227		$ 39,705
Foreign currency impact				(355)
Payments	[1]			(8,852)
Fair value adjustment		(7,227)	[2]	(23,271)	[3]
Balance at end of period		$ 0		$ 7,227

[1] During the year ended December 31, 2020, Teradyne paid $8.9 million of contingent consideration for the earn-out in connection with the acquisition of Mobile Industrial Robots (“MiR”).

[2] During the year ended December 31, 2021, the fair value of contingent consideration for the earn-outs in connection with the acquisition of AutoGuide was reduced to zero, which resulted in a benefit of $7.2 million, primarily due to a decrease in forecasted revenues and earnings before interest and taxes. As of December 31, 2021, the maximum amount of contingent consideration that could be paid in connection with the acquisition of AutoGuide is $100.2 million. The remaining earn-out period ends on December 31, 2022. The sellers of AutoGuide have filed an arbitration claim against Teradyne related to allegations of non-compliance with its earn-out obligations. The ultimate amount of contingent consideration for the earn-outs in connection with the acquisition of AutoGuide may be affected by the outcome of the arbitration (see Note M: “Commitments and Contingencies”).

[3] During the year ended December 31, 2020, the fair value of contingent consideration for the earn-out in connection with the acquisition of AutoGuide was decreased by $19.7 million primarily due to a decrease in forecasted revenues and earnings before interest and taxes. During the year ended December 31, 2020, the fair value of contingent consideration for the earn-out in connection with the acquisition of MiR was decreased by $3.5 million primarily due to a decrease in forecasted revenues.