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Computation of Basic and Diluted Net Income (loss) Per Common Share (Parenthetical) (Detail) - Convertible Notes shares in Millions	3 Months Ended	9 Months Ended
	Oct. 01, 2017 $ / shares shares	Oct. 01, 2017 $ / shares shares
Net Income Loss Per Common Share
Initial debt conversion price | $ / shares	$ 31.84	$ 31.84
Shares that would be issued upon conversion | shares	14.4	14.4

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- Definition

Antidilution adjustments of convertible note hedges.

+ References

No definition available.

+ Details

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Namespace Prefix:	ter_
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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
Period Type:	duration

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- Definition

The price per share of the conversion feature embedded in the debt instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6928298&loc=SL6031898-161870

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	na
Period Type:	instant

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- Details

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