Equity Method Investment	9 Months Ended
Sep. 28, 2025
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investment	F. EQUITY METHOD INVESTMENT On May 27, 2024, Teradyne paid 483.1 million Euros, equivalent to $524.1 million, to purchase a combination of previously issued and outstanding shares and shares newly issued by Technoprobe, S.p.A. ("Technoprobe"). The shares purchased represent 10% of the issued and outstanding shares of Technoprobe. Teradyne also received a board seat as part of the purchase. Teradyne accounts for this investment using the equity method as a result of being able to exercise significant influence over the operating and financial decisions of Technoprobe. The carrying value of this equity method investment as of September 28, 2025, was $538.0 million and $494.5 million as of December 31, 2024 in the condensed consolidated balance sheets. For the three months ended September 28, 2025, Teradyne recorded a $5.2 million loss related to equity in net earnings of affiliate and a $2.2 million loss in other comprehensive income (loss) related to investment. For the nine months ended September 28, 2025, Teradyne recorded a $16.7 million loss related to equity in net earnings of affiliate and an income of $60.2 million of other comprehensive income (loss) related to the equity method investment. For the three and nine months ended September 29, 2024, Teradyne recorded a loss of $1.1 million of equity in net earnings of affiliate and income of $15.4 million in other comprehensive income (loss) related this investment. Based on the quoted closing price of Technoprobe stock as of September 28, 2025, the fair value of the publicly traded investment was $638.2 million. Teradyne's equity method basis difference was calculated as the difference between the investment and the amount of underlying equity in net assets acquired. The basis differences, net of tax, will be amortized over the estimated useful lives. Teradyne made an accounting policy election to report its share of Technoprobe's results on a 3-month lag, which is applied consistently from period to period. Teradyne records its share of Technoprobe's net income or loss and the amortization of equity method basis difference, as 'Equity in net earnings of affiliate' in the condensed consolidated statements of operations. Teradyne includes its share of Technoprobe's other comprehensive income and a cumulative translation adjustment in the condensed consolidated statements of comprehensive income.

Equity Method Investment

9 Months Ended

Sep. 28, 2025

Equity Method Investments and Joint Ventures [Abstract]

F. EQUITY METHOD INVESTMENT

On May 27, 2024, Teradyne paid 483.1 million Euros, equivalent to $524.1 million, to purchase a combination of previously issued and outstanding shares and shares newly issued by Technoprobe, S.p.A. ("Technoprobe"). The shares purchased represent 10% of the issued and outstanding shares of Technoprobe. Teradyne also received a board seat as part of the purchase. Teradyne accounts for this investment using the equity method as a result of being able to exercise significant influence over the operating and financial decisions of Technoprobe.

The carrying value of this equity method investment as of September 28, 2025, was $538.0 million and $494.5 million as of December 31, 2024 in the condensed consolidated balance sheets. For the three months ended September 28, 2025, Teradyne recorded a $5.2 million loss related to equity in net earnings of affiliate and a $2.2 million loss in other comprehensive income (loss) related to investment. For the nine months ended September 28, 2025, Teradyne recorded a $16.7 million loss related to equity in net earnings of affiliate and an income of $60.2 million of other comprehensive income (loss) related to the equity method investment. For the three and nine months ended September 29, 2024, Teradyne recorded a loss of $1.1 million of equity in net earnings of affiliate and income of $15.4 million in other comprehensive income (loss) related this investment.

Based on the quoted closing price of Technoprobe stock as of September 28, 2025, the fair value of the publicly traded investment was $638.2 million.

Teradyne's equity method basis difference was calculated as the difference between the investment and the amount of underlying equity in net assets acquired. The basis differences, net of tax, will be amortized over the estimated useful lives.

Teradyne made an accounting policy election to report its share of Technoprobe's results on a 3-month lag, which is applied consistently from period to period. Teradyne records its share of Technoprobe's net income or loss and the amortization of equity method basis difference, as 'Equity in net earnings of affiliate' in the condensed consolidated statements of operations. Teradyne includes its share of Technoprobe's other comprehensive income and a cumulative translation adjustment in the condensed consolidated statements of comprehensive income.