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Income Taxes - Additional Information (Detail) (USD $) | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Dec. 31, 2014 | Sep. 28, 2014 | Jun. 29, 2014 | Mar. 30, 2014 | Dec. 31, 2013 | Sep. 29, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income tax expense (benefit) from operations, total | $ (21,002,000)us-gaap_IncomeTaxExpenseBenefit | [1],[2],[3] | $ 17,721,000 us-gaap_IncomeTaxExpenseBenefit | [1],[4] | $ 20,187,000 us-gaap_IncomeTaxExpenseBenefit | [1] | $ (2,802,000)us-gaap_IncomeTaxExpenseBenefit | $ 13,096,000 us-gaap_IncomeTaxExpenseBenefit | [5],[6] | $ 18,093,000 us-gaap_IncomeTaxExpenseBenefit | $ 13,801,000 us-gaap_IncomeTaxExpenseBenefit | $ (8,015,000)us-gaap_IncomeTaxExpenseBenefit | $ 14,104,000 us-gaap_IncomeTaxExpenseBenefit | $ 36,975,000 us-gaap_IncomeTaxExpenseBenefit | $ 48,927,000 us-gaap_IncomeTaxExpenseBenefit |
U.S. research and development tax credit reduction Percentage |  |  |  |  |  |  |  |  |  |  |  |  | (7.90%)us-gaap_EffectiveIncomeTaxRateReconciliationTaxCreditsResearch | (7.20%)us-gaap_EffectiveIncomeTaxRateReconciliationTaxCreditsResearch |  |
U.S. statutory federal tax rate |  |  |  |  |  |  |  |  |  |  |  |  | 35.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate | 35.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate | 35.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate |
Tax savings due to the tax holiday |  |  |  |  |  |  |  |  |  |  |  |  | 13,200,000 us-gaap_IncomeTaxReconciliationTaxHolidays | 4,700,000 us-gaap_IncomeTaxReconciliationTaxHolidays | 10,900,000 us-gaap_IncomeTaxReconciliationTaxHolidays |
Tax savings due to the tax holiday, per share |  |  |  |  |  |  |  |  |  |  |  |  | $ 0.06 us-gaap_IncomeTaxHolidayIncomeTaxBenefitsPerShare | $ 0.02 us-gaap_IncomeTaxHolidayIncomeTaxBenefitsPerShare | $ 0.05 us-gaap_IncomeTaxHolidayIncomeTaxBenefitsPerShare |
Tax holiday expiration date |  |  |  |  |  |  |  |  |  |  |  |  | December 31, 2015 |  |  |
Accrued interest and penalties | 600,000 us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued |  |  |  |  |  |  | 400,000 us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued |  |  |  |  | 600,000 us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued | 400,000 us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued |  |
Interest and penalties related to income tax |  |  |  |  |  |  |  |  |  |  |  |  | 200,000 us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense | 200,000 us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense | 100,000 us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense |
Valuation allowance amount decrease/increase |  |  |  |  |  |  |  |  |  |  |  |  | 1,300,000 us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount | (19,500,000)us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount |  |
Valuation allowance includes net deferred tax assets | 41,737,000 us-gaap_DeferredTaxAssetsValuationAllowance |  |  |  |  |  |  | 40,386,000 us-gaap_DeferredTaxAssetsValuationAllowance |  |  |  |  | 41,737,000 us-gaap_DeferredTaxAssetsValuationAllowance | 40,386,000 us-gaap_DeferredTaxAssetsValuationAllowance |  |
U.S. Federal operating loss carryforwards | 11,504,000 us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic |  |  |  |  |  |  |  |  |  |  |  | 11,504,000 us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic |  |  |
Net operating loss carryforward excess tax deductions related to stock based compensation | 0 ter_NetOperatingLossCarryforwardExcessTaxDeductionRelatedToStockBasedCompensation |  |  |  |  |  |  |  |  |  |  |  | 0 ter_NetOperatingLossCarryforwardExcessTaxDeductionRelatedToStockBasedCompensation |  |  |
Tax credit carry forwards, approximately | 140,800,000 us-gaap_TaxCreditCarryforwardAmount |  |  |  |  |  |  |  |  |  |  |  | 140,800,000 us-gaap_TaxCreditCarryforwardAmount |  |  |
Tax credits carry forwards | 50,554,000 us-gaap_DeferredTaxAssetsTaxCreditCarryforwards |  |  |  |  |  |  | 65,210,000 us-gaap_DeferredTaxAssetsTaxCreditCarryforwards |  |  |  |  | 50,554,000 us-gaap_DeferredTaxAssetsTaxCreditCarryforwards | 65,210,000 us-gaap_DeferredTaxAssetsTaxCreditCarryforwards |  |
Alternative minimum tax credits carry forwards | 6,600,000 ter_DeferredTaxAssetsAlternativeMinimumTaxCreditsCarryforwards |  |  |  |  |  |  |  |  |  |  |  | 6,600,000 ter_DeferredTaxAssetsAlternativeMinimumTaxCreditsCarryforwards |  |  |
Unrecognized tax benefits | 30,418,000 us-gaap_UnrecognizedTaxBenefits |  |  |  |  |  |  | 21,203,000 us-gaap_UnrecognizedTaxBenefits |  |  |  |  | 30,418,000 us-gaap_UnrecognizedTaxBenefits | 21,203,000 us-gaap_UnrecognizedTaxBenefits | 18,666,000 us-gaap_UnrecognizedTaxBenefits | 19,391,000 us-gaap_UnrecognizedTaxBenefits
Unrecognized tax benefits, if recognized would impact effective tax rate | 24,100,000 us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate |  |  |  |  |  |  |  |  |  |  |  | 24,100,000 us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate |  |  |
Unrecognized tax benefits, if recognized would impact valuation allowance | 6,300,000 ter_UnrecognizedTaxBenefitsIfRecognizedWouldImpactValuationAllowance |  |  |  |  |  |  |  |  |  |  |  | 6,300,000 ter_UnrecognizedTaxBenefitsIfRecognizedWouldImpactValuationAllowance |  |  |
Decrease in unrecognized tax benefits |  |  |  |  |  |  |  |  |  |  |  |  | 800,000 ter_IncreaseDecreaseInUnrecognizedTaxBenefit |  |  |
Deferred tax liability not been established | 556,900,000 us-gaap_DeferredTaxLiabilityNotRecognizedAmountOfUnrecognizedDeferredTaxLiabilityUndistributedEarningsOfForeignSubsidiaries |  |  |  |  |  |  |  |  |  |  |  | 556,900,000 us-gaap_DeferredTaxLiabilityNotRecognizedAmountOfUnrecognizedDeferredTaxLiabilityUndistributedEarningsOfForeignSubsidiaries |  |  |
General Business Tax Credit Carryforward |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credits carry forwards | 37,000,000 us-gaap_DeferredTaxAssetsTaxCreditCarryforwards / us-gaap_TaxCreditCarryforwardAxis = us-gaap_GeneralBusinessMember |  |  |  |  |  |  |  |  |  |  |  | 37,000,000 us-gaap_DeferredTaxAssetsTaxCreditCarryforwards / us-gaap_TaxCreditCarryforwardAxis = us-gaap_GeneralBusinessMember |  |  |
Foreign |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credits carry forwards | 27,500,000 us-gaap_DeferredTaxAssetsTaxCreditCarryforwards / us-gaap_TaxCreditCarryforwardAxis = us-gaap_ForeignCountryMember |  |  |  |  |  |  |  |  |  |  |  | 27,500,000 us-gaap_DeferredTaxAssetsTaxCreditCarryforwards / us-gaap_TaxCreditCarryforwardAxis = us-gaap_ForeignCountryMember |  |  |
State and Local Jurisdiction |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credits carry forwards | 69,700,000 us-gaap_DeferredTaxAssetsTaxCreditCarryforwards / us-gaap_TaxCreditCarryforwardAxis = us-gaap_StateAndLocalJurisdictionMember |  |  |  |  |  |  |  |  |  |  |  | 69,700,000 us-gaap_DeferredTaxAssetsTaxCreditCarryforwards / us-gaap_TaxCreditCarryforwardAxis = us-gaap_StateAndLocalJurisdictionMember |  |  |
Stock Option |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credits carry forwards | 46,600,000 us-gaap_DeferredTaxAssetsTaxCreditCarryforwards / us-gaap_TaxCreditCarryforwardAxis = us-gaap_StockOptionMember |  |  |  |  |  |  |  |  |  |  |  | 46,600,000 us-gaap_DeferredTaxAssetsTaxCreditCarryforwards / us-gaap_TaxCreditCarryforwardAxis = us-gaap_StockOptionMember |  |  |
GenRad, Inc. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. Federal operating loss carryforwards | 10,700,000 us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic / us-gaap_BusinessAcquisitionAxis = ter_GenradIncMember |  |  |  |  |  |  |  |  |  |  |  | 10,700,000 us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic / us-gaap_BusinessAcquisitionAxis = ter_GenradIncMember |  |  |
ZTEC Instruments, Inc. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. Federal operating loss carryforwards | $ 800,000 us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic / us-gaap_BusinessAcquisitionAxis = ter_ZtecCorporationMember |  |  |  |  |  |  |  |  |  |  |  | $ 800,000 us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic / us-gaap_BusinessAcquisitionAxis = ter_ZtecCorporationMember |  |  |
Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credit carry forward, expiration date |  |  |  |  |  |  |  |  |  |  |  |  | 2017 |  |  |
Minimum | Foreign |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credit carry forward, expiration date |  |  |  |  |  |  |  |  |  |  |  |  | 2018 |  |  |
Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credit carry forward, expiration date |  |  |  |  |  |  |  |  |  |  |  |  | 2034 |  |  |
Maximum | Foreign |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credit carry forward, expiration date |  |  |  |  |  |  |  |  |  |  |  |  | 2022 |  |  |
[1] | Dividends declared by Teradyne's Board of Directors were paid in each of the second, third and fourth quarters of 2014.
[2] | In the fourth quarter ended December 31, 2014, Teradyne recorded pension and post retirement net actuarial losses of $46.6 million. See Note B: "Accounting Policies" for a discussion of our accounting policy.
[3] | In the fourth quarter ended December 31, 2014, Teradyne recorded a goodwill impairment charge of $98.9 million in its Wireless Test segment.
[4] | Restructuring and other includes a $(0.6) million fair value adjustment to decrease the ZTEC acquisition contingent consideration.
[5] | Other (income) expense, net includes a $34.2 million gain from the sale of an equity investment.
[6] | In the fourth quarter ended December 31, 2013, Teradyne recorded pension and post retirement net actuarial gains of $9.0 million. See Note B: "Accounting Policies" for a discussion of our accounting policy.

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- Definition The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319 + Details
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