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Computation of Basic and Diluted Net (Loss) Income Per Common Share (Parenthetical) (Detail) - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2014
Convertible Notes
Net Income Loss Per Common Share
Initial debt conversion price	$ 5.48	$ 5.48
Shares that would be issued upon conversion	34.7	34.7
Convertible Notes Hedge Warrant
Net Income Loss Per Common Share
Initial debt conversion price	$ 7.67	$ 7.67
Shares that would be issued upon conversion	34.7	34.7

X

- 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
Period Type:	duration

X

- 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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Balance Type:	na
Period Type:	instant

X

- Details

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Namespace Prefix:
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X

- Details

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