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Schedule of Weighted Average Assumptions to Determine Pension Obligations (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Postretirement Benefit Plans
Schedule of Benefit Obligations Weighted Average Assumptions [Line Items]
Discount rate	3.50%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember	4.10%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember	3.10%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Initial Medical Trend	7.50%ter_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationInitialMedicalTrend / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember	8.00%ter_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationInitialMedicalTrend / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember	8.50%ter_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationInitialMedicalTrend / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Ultimate Health Care Trend	5.00%us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember	5.00%us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember	5.00%us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Medical cost trend rate decrease to ultimate rate in year	2022	2020	2020
Defined Benefit Pension Plans | United States
Schedule of Benefit Obligations Weighted Average Assumptions [Line Items]
Discount rate	3.70%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_StatementGeographicalAxis = us-gaap_DomesticCountryMember	4.50%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_StatementGeographicalAxis = us-gaap_DomesticCountryMember
Salary progression rate	2.90%ter_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationSalaryProgressionRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_StatementGeographicalAxis = us-gaap_DomesticCountryMember	3.00%ter_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationSalaryProgressionRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_StatementGeographicalAxis = us-gaap_DomesticCountryMember
Defined Benefit Pension Plans | Foreign
Schedule of Benefit Obligations Weighted Average Assumptions [Line Items]
Discount rate	2.60%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_StatementGeographicalAxis = us-gaap_ForeignCountryMember	3.80%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_StatementGeographicalAxis = us-gaap_ForeignCountryMember
Salary progression rate	3.20%ter_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationSalaryProgressionRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_StatementGeographicalAxis = us-gaap_ForeignCountryMember	3.50%ter_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationSalaryProgressionRate / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_StatementGeographicalAxis = us-gaap_ForeignCountryMember

X

- Definition

Defined benefit plan assumptions used calculating benefit obligation initial medical trend.

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- Definition

Defined benefit plan assumptions used calculating benefit obligation medical cost trend rate decrease to ultimate rate in year.

+ References

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- Definition

Defined benefit plan assumptions used calculating benefit obligation salary progression rate.

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X

- Definition

The interest rate used to adjust for the time value of money for the plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(1)

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- Definition

The ultimate trend rate for health care costs.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (l)

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