Financial Instruments And Derivatives (Schedule Of Changes In Fair Value Of Level 3 Financial Assets) (Details) (USD $) In Thousands			3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
Jul. 03, 2011	Dec. 31, 2010	Jul. 04, 2010 Long-Term Auction Rate Securities [Member] Fair Value Inputs Level 3 [Member]	Jul. 04, 2010 Long-Term Auction Rate Securities [Member] Fair Value Inputs Level 3 [Member]	Jul. 04, 2010 UBS Put [Member] Fair Value Inputs Level 3 [Member]	Jul. 04, 2010 UBS Put [Member] Fair Value Inputs Level 3 [Member]	Jul. 03, 2011 Fair Value Inputs Level 3 [Member]
Balance at beginning of period	$ 1,049,693	$ 934,207	$ 23,697	$ 23,649	$ 2,687	$ 2,830
Sale of auction rate securities and exercise of UBS Put			(20,863)	(21,013)	(2,687)	(2,687)
Change in unrealized gain included in interest income			2	200
Change in unrealized loss included in interest expense and other						(143)
Balance at end of period	$ 1,049,693	$ 934,207	$ 2,836	$ 2,836

Change in unrealized loss included in interest expense and other.

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Namespace Prefix:	ter
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the amount of the total change in unrealized (holding) gains or losses for the period which are included in the statement of income (or changes in net assets) in investment income. Such unrealized (holding) gains or losses relate to those assets still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 157
-Paragraph 32
-Subparagraph d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Sales that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration