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Savings Plan - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Savings Plan [Line Items]
Savings plan maximum percentage of employees contribution allowable	20.00%ter_SavingsPlanMaximumPercentageOfEmployeesContributionAllowable
Percentage of employer contributions vested per year	25.00%us-gaap_DefinedContributionPlanEmployersMatchingContributionAnnualVestingPercentage
Maximum employment period considered for vesting of employers' contribution, in years	4ter_MaximumEmploymentPeriodConsideredForVestingOfEmployersContribution
U.S. Qualified Pension Plan
Savings Plan [Line Items]
Maximum percentage of matching contributions made by the employer	100.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = ter_USQualifiedPensionPlanMember	100.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = ter_USQualifiedPensionPlanMember	100.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = ter_USQualifiedPensionPlanMember
Percentage of employer match on employee contribution	4.00%us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = ter_USQualifiedPensionPlanMember	4.00%us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = ter_USQualifiedPensionPlanMember	4.00%us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = ter_USQualifiedPensionPlanMember
Savings Plan
Savings Plan [Line Items]
Amounts charged to statement of operations	12.8us-gaap_DefinedContributionPlanCostRecognized / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = ter_SavingsPlanMember	12.0us-gaap_DefinedContributionPlanCostRecognized / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = ter_SavingsPlanMember	10.6us-gaap_DefinedContributionPlanCostRecognized / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = ter_SavingsPlanMember

X

- Definition

Maximum employment period considered for vesting of employers' contribution

+ References

No definition available.

+ Details

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Namespace Prefix:	ter_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Details

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Namespace Prefix:	ter_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Savings plan maximum percentage of employees contribution allowable

+ References

No definition available.

+ Details

Name:	ter_SavingsPlanMaximumPercentageOfEmployeesContributionAllowable
Namespace Prefix:	ter_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Percentage employer matches of the employee's percentage contribution matched.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Percentage of employer's matching contributions to a defined contribution plan that vests in a given year.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=ter_USQualifiedPensionPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: