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v3.21.2

Computation of Basic and Diluted Net Income Per Common Share (Parenthetical) (Detail) - $ / shares shares in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Oct. 03, 2021 | Oct. 03, 2021
Convertible Notes |  |
Net Income Loss Per Common Share |  |
Debt instrument, convertible, stock price trigger | $ 31.53 | $ 31.54
Shares that would be issued upon conversion | 8.7 | 11.7
Convertible Notes Hedge Warrant |  |
Net Income Loss Per Common Share |  |
Debt instrument, convertible, stock price trigger | $ 39.56 | $ 39.58
Shares that would be issued upon conversion | 14.6 | 14.6

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- Definition Antidilution adjustments of convertible note hedges. + References No definition available. + Details
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Namespace Prefix: | ter_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

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- Definition Net Income (Loss) Per Common Share [Line Items] + References No definition available. + Details
Name: | ter_NetIncomeLossPerCommonShareLineItems
Namespace Prefix: | ter_
Data Type: | xbrli:stringItemType
Balance Type: | na
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- Definition Price of the entity's common stock which would be required to be attained for the conversion feature embedded in the debt instrument to become effective. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | na
Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_DebtInstrumentAxis=ter_ConvertibleNotesHedgeAndWarrantMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |