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v3.20.4

Debt - Additional Information (Detail) |  |  |  | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Feb. 22, 2021 USD ($) Holders | May 01, 2020 USD ($) | Dec. 12, 2016 USD ($) Customer shares | Dec. 31, 2020 USD ($) $ / shares shares | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2016 USD ($) | Apr. 27, 2015 USD ($)
Debt Instrument |  |  |  |  |  |  |  |
Repurchase of common stock |  |  |  | $ 88,465,000 | $ 500,000,000 | $ 823,478,000 |  |
Line of Credit Facility, Maximum Borrowing Capacity |  | $ 400,000,000.0 |  |  |  |  |  |
Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases |  | $ 150,000,000.0 |  |  |  |  |  |
Line of Credit Facility, Interest Rate Description |  | The interest rate applicable to loans under the Credit Facility are, at Teradyne’s option, equal to either a base rate plus a margin ranging from 0.50% to 1.25% per annum or LIBOR, a minimum of 0.75%, plus a margin ranging from 1.50% to 2.25% per annum, based on the consolidated leverage ratio of Teradyne. In addition, Teradyne will pay a commitment fee on the unused portion of the commitments under the Credit Facility ranging from 0.25% to 0.40% per annum, based on the then applicable consolidated leverage ratio. |  |  |  |  |  |
Term of revolving credit facility |  |  |  | 3 years |  |  |  |
Convertible common shares |  |  |  | $ 3,787,000 |  |  |  |
Convertible Common Shares [Member] |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |
Convertible common shares |  |  |  | 37,000,000 |  |  |  |
Collateral Pledged [Member] |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |
Line of Credit Facility, Interest Rate Description |  | 65 |  |  |  |  |  |
1.25% Convertible Senior Unsecured Notes Due December 15, 2023 |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |
Aggregate principal amount |  |  | $ 460,000,000.0 | 459,971,000 | $ 460,000,000 |  |  |
Debt instrument, interest rate, stated percentage |  |  | 1.25% |  |  |  |  |
Debt instrument, net proceeds after issuance costs |  |  | $ 450,800,000 |  |  |  |  |
Payment for net cost of convertible note hedges net of warrant proceeds |  |  | 33,000,000.0 | $ 33,000,000.0 |  |  |  |
Repurchase of common stock |  |  | $ 50,100,000 |  |  |  |  |
Repurchase of stock, shares | shares |  |  | 2,000,000.0 |  |  |  |  |
Senior notes maturity date |  |  | Dec. 15, 2023 |  |  |  |  |
Debt instrument, frequency of periodic payment |  |  | payable semiannually in arrears on June 15 and December 15 of each year |  |  |  |  |
Debt instrument, conversion option expiration date |  |  | Sep. 15, 2023 |  |  |  |  |
Debt instrument conversion price | $ / shares |  |  |  | $ 31.56 |  |  |  |
Shares that would be issued upon conversion | shares |  |  |  | 14,600,000 |  |  |  |
Strike price per share of warrant | $ / shares |  |  |  | $ 39.60 |  |  |  |
Debt instrument, convertible, carrying amount of equity component |  |  |  | $ 100,800,000 |  |  |  |
Debt instrument, effective annual interest rate |  |  |  | 5.00% |  |  |  |
Financing cost |  |  |  | $ 3,300,000 |  |  | $ 7,200,000 |
Debt issuance costs, amortization period |  |  |  | 7 years |  |  |  |
Unamortized discount |  |  |  | $ 49,900,000 |  |  |  |
Debt Instrument, convertible, remaining discount amortization period |  |  |  | 3 years |  |  |  |
Value of notes converted |  |  |  | $ 1,747,500,000 |  |  |  |
1.25% Convertible Senior Unsecured Notes Due December 15, 2023 | Subsequent Event |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |
Number of holders excerised the conversion option | Holders | 24 |  |  |  |  |  |  |
Debt instrument conversion converted instrument amount | $ 51,000,000.0 |  |  |  |  |  |  |
1.25% Convertible Senior Unsecured Notes Due December 15, 2023 | Conversion option one |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |
Trading days measurement period | Customer |  |  | 20 |  |  |  |  |
Consecutive trading days measurement period | Customer |  |  | 30 |  |  |  |  |
Percentage of conversion price |  |  | 130.00% |  |  |  |  |
1.25% Convertible Senior Unsecured Notes Due December 15, 2023 | Conversion option two |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |
Aggregate principal amount |  |  | $ 1,000,000 |  |  |  |  |
Trading days measurement period | Customer |  |  | 5 |  |  |  |  |
Consecutive trading days measurement period | Customer |  |  | 5 |  |  |  |  |
Percentage of closing sale price of common stock and conversion rate product |  |  | 98.00% |  |  |  |  |
Revolving Credit Facility |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |
Term of loan, years |  |  |  | 5 years |  |  |  |
Credit facility, borrowing capacity |  |  |  |  |  |  |  | $ 350,000,000
Revolving Credit Facility | Maximum | Truist Bank [Member] |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |
Commitment fee percentage of unused portion of credit facility |  |  |  | 0.40% |  |  |  |
Revolving Credit Facility | Minimum | Truist Bank [Member] |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |
Commitment fee percentage of unused portion of credit facility |  |  |  | 0.25% |  |  |  |
Revolving Credit Facility | Base Rate | Maximum | Truist Bank [Member] |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |
Debt instrument, basis spread on variable rate |  |  |  | 1.25% |  |  |  |
Revolving Credit Facility | Base Rate | Minimum | Truist Bank [Member] |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |
Debt instrument, basis spread on variable rate |  |  |  | 0.50% |  |  |  |
Revolving Credit Facility | London Interbank Offered Rate (LIBOR) | Truist Bank [Member] |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |
Debt Instrument Base Rate Percentage |  |  |  | 0.75% |  |  |  |
Revolving Credit Facility | London Interbank Offered Rate (LIBOR) | Maximum | Truist Bank [Member] |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |
Debt instrument, basis spread on variable rate |  |  |  | 2.25% |  |  |  |
Revolving Credit Facility | London Interbank Offered Rate (LIBOR) | Minimum | Truist Bank [Member] |  |  |  |  |  |  |  |
Debt Instrument |  |  |  |  |  |  |  |
Debt instrument, basis spread on variable rate |  |  |  | 1.50% |  |  |  |

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- Definition The value of the financial instrument(s) that the original debt is being converted into in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=121583591&loc=d3e4304-108586 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=121583591&loc=d3e4332-108586 + Details
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