Schedule of Available for Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Oct. 04, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	$ 781,610	$ 1,000,625
Available-for-sale marketable securities, Unrealized Gain	3,252	4,818
Available-for-sale marketable securities, Unrealized (Loss)	(1,921)	(867)
Available-for-sale marketable securities, Fair Market Value	782,941	1,004,576
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	73,034	583,076
U.S. Treasury Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	349,464	402,197
Available-for-sale marketable securities, Unrealized Gain	385	362
Available-for-sale marketable securities, Unrealized (Loss)	(196)	(405)
Available-for-sale marketable securities, Fair Market Value	349,653	402,154
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	19,260	317,771
U.S. Government Agency Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	213,149	258,452
Available-for-sale marketable securities, Unrealized Gain	342	135
Available-for-sale marketable securities, Unrealized (Loss)		(85)
Available-for-sale marketable securities, Fair Market Value	213,491	258,502
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses		104,642
Corporate Debt Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	115,130	139,374
Available-for-sale marketable securities, Unrealized Gain	1,305	2,414
Available-for-sale marketable securities, Unrealized (Loss)	(1,628)	(321)
Available-for-sale marketable securities, Fair Market Value	114,807	141,467
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	48,369	96,998
Commercial Paper
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	45,498	140,616
Available-for-sale marketable securities, Unrealized Gain	12	26
Available-for-sale marketable securities, Unrealized (Loss)		(4)
Available-for-sale marketable securities, Fair Market Value	45,510	140,638
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses		41,747
Certificates of Deposit and Time Deposits
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	45,652	49,048
Available-for-sale marketable securities, Unrealized Gain	25	11
Available-for-sale marketable securities, Unrealized (Loss)		(23)
Available-for-sale marketable securities, Fair Market Value	45,677	49,036
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	3,505	20,684
Equity And Debt Mutual Funds
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	12,291	10,492
Available-for-sale marketable securities, Unrealized Gain	1,183	1,870
Available-for-sale marketable securities, Unrealized (Loss)	(97)	(29)
Available-for-sale marketable securities, Fair Market Value	13,377	12,333
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	1,900	1,234
Non-U.S. Government Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	426	446
Available-for-sale marketable securities, Fair Market Value	$ 426	$ 446

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562

+ Details

Name:	us-gaap_AvailableForSaleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAmortizedCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 6

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_EligibleItemOrGroupForFairValueOptionAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EligibleItemOrGroupForFairValueOptionAxis=us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EligibleItemOrGroupForFairValueOptionAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EligibleItemOrGroupForFairValueOptionAxis=us-gaap_CommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EligibleItemOrGroupForFairValueOptionAxis=us-gaap_CertificatesOfDepositMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EligibleItemOrGroupForFairValueOptionAxis=ter_EquityAndDebtMutualFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EligibleItemOrGroupForFairValueOptionAxis=us-gaap_ForeignCorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: