Accounting Policies (Policies)	9 Months Ended
Accounting Policies (Policies)	Oct. 02, 2022
Basis of Presentation	Basis of Presentation The consolidated interim financial statements include the accounts of Teradyne and its wholly owned subsidiaries. All significant intercompany balances and transactions have been eliminated. These interim financial statements are unaudited and reflect all normal recurring adjustments that are, in the opinion of management, necessary for the fair statement of such interim financial statements. Certain prior year amounts may have been reclassified to conform to the current year presentation. The December 31, 2021 condensed consolidated balance sheet data was derived from audited financial statements but does not include all disclosures required by United States of America generally accepted accounting principles (“U.S. GAAP”) for complete financial statements. The accompanying financial information should be read in conjunction with the consolidated financial statements and notes thereto contained in Teradyne’s Annual Report on Form 10-K, filed with the U.S. Securities and Exchange Commission (“SEC”) on February 23, 2022, for the year ended December 31, 2021.
Preparation of Financial Statements and Use of Estimates	Preparation of Financial Statements and Use of Estimates The preparation of consolidated financial statements requires management to make estimates and judgments that affect the amounts of assets, liabilities, revenues and expenses, and related disclosures of contingent liabilities. On an on-going basis, management evaluates its estimates, including those related to inventories, investments, goodwill, intangible and other long-lived assets, accounts receivable, income taxes, deferred tax assets and liabilities, pensions, warranties, and loss contingencies. Management bases its estimates on historical experience and on appropriate and customary assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgements about the carrying values of assets and liabilities that are not readily apparent from other sources. Due to the COVID-19 pandemic, there has been uncertainty and disruption in the global economy and our markets. Management is not aware of any specific event or circumstance that would require an update to its estimates or judgments or a revision of the carrying value of its assets or liabilities as of the date of issuance of this Quarterly Report on Form 10-Q. These estimates may change, as new events occur and additional information is obtained. Actual results may differ significantly from these estimates under different assumptions or conditions.
Convertible Debt	Convertible Debt Teradyne adopted Accounting Standards Update (“ASU”) ASU 2020-06 – “Debt—Debt with Conversion and Other Options and Derivatives and Hedging—Contracts in Entity’s Own Equity,” on January 1, 2022 using the modified retrospective method of adoption . Under ASU 2020-06, Teradyne accounts for a convertible debt instrument as a single liability measured at its amortized cost, as long as no other features require bifurcation and recognition as derivatives. Unsettled shares are recorded in current debt, and there is no recognition of a debt discount, which was previously amortized to interest expense. Teradyne uses the if-converted method in the diluted earnings per share (“EPS”) calculation for convertible instruments. As a result of adoption, Teradyne recorded an increase of $1.4 million to current debt for unsettled shares, an increase of $6.6 million to long-term debt for unamortized debt discount, an increase of $1.8 million to deferred tax assets and an increase to retained earnings of $94.6 million for the reclassification of the equity component. Mezzanine equity representing unsettled shares value was reduced to zero and additional paid-in capital was reduced by $100.8 million.