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Stock Based Compensation - Additional Information (Detail) (USD $)	1 Months Ended					6 Months Ended		12 Months Ended			1 Months Ended	12 Months Ended	0 Months Ended
	Jul. 31, 2014	Jan. 31, 2014	Jul. 31, 2013	Jan. 31, 2013	Jul. 31, 2012	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2015	Jan. 31, 2014 Age	May 21, 2013	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2013	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2011	Jan. 24, 2014
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted								1,870,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	2,110,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	1,844,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Weighted average grant date fair value of restricted stock units granted								$ 19.30us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	$ 16.53us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	$ 16.67us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Stock options granted								89,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod	213,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod	151,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod
Weighted average grant date fair value						$ 3.42us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	$ 4.09us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	$ 5.49us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	$ 6.09us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	$ 6.85us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Total unrecognized expense related to non-vested restricted stock unit awards and stock options								$ 51,300,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Unrecognized expense related to non-vested restricted stock unit awards and stock options expected to be recognized over weighted average period, in years								2 years 4 months 24 days
Stock based compensation expense related to retirement agreement		6,600,000us-gaap_AllocatedShareBasedCompensationExpense
Maximum percent of shares allowed to purchase								10.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate
Fair market value								$ 25,000ter_MaximumSharesCanBePurchasedUnderPlanAtFairMarketValue
Maximum number of shares allowed to purchase								6,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee
Percentage of common stock price paid								85.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent	85.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent	85.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent
Common stock issued to employees	500,000us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans	400,000us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans	400,000us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans	600,000us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans	600,000us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
Value of common stock issued to employees per share							$ 11.91ter_ValueOfCommonStockIssuedToEmployeesPerShare							$ 16.82ter_ValueOfCommonStockIssuedToEmployeesPerShare	$ 16.66ter_ValueOfCommonStockIssuedToEmployeesPerShare	$ 14.98ter_ValueOfCommonStockIssuedToEmployeesPerShare	$ 14.94ter_ValueOfCommonStockIssuedToEmployeesPerShare	$ 11.69ter_ValueOfCommonStockIssuedToEmployeesPerShare
Number of shares available for grant						6,414,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant		12,443,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	14,213,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	6,414,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant									8,205,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award
Common stock issued to employees											500,000us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted								1,870,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember	2,110,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember	1,844,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember
Restricted Stock Units | Employees
Share-based Compensation Arrangement by Share-based Payment Award
Period of stock granted to employees and executive officers vest in equal installments								4 years
Restricted Stock Units | Director
Share-based Compensation Arrangement by Share-based Payment Award
Period of stock granted to employees and executive officers vest in equal installments								1 year
Percentage of awards vesting on the first anniversary of grant date								100.00%ter_ShareBasedCompensationArrangementByShareBasedPaymentAwardVestingPercentageUponOneYearAnniversaryOfDateOfGrant / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember
TSR Performance-Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Total shareholder return performance measurement period												3 years
Minimum age of retirement to be eligible for PRSUs												60ter_MinimumRetirementAgeForEligibleEmployeesOfPostretirementPlans / us-gaap_AwardTypeAxis = ter_TotalShareholderReturnPerformanceBasedRestrictedStockUnitsMember
Minimum years of service for retirement to be eligible for PRSUs												10 years
Restricted stock unit awards granted								100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = ter_TotalShareholderReturnPerformanceBasedRestrictedStockUnitsMember
Weighted average grant date fair value of restricted stock units granted								$ 22.06us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = ter_TotalShareholderReturnPerformanceBasedRestrictedStockUnitsMember
Estimated annual dividend amount per share								$ 0.24us-gaap_FairValueAssumptionsExpectedDividendPayments / us-gaap_AwardTypeAxis = ter_TotalShareholderReturnPerformanceBasedRestrictedStockUnitsMember
Stock price																				$ 19.16us-gaap_SharePrice / us-gaap_AwardTypeAxis = ter_TotalShareholderReturnPerformanceBasedRestrictedStockUnitsMember
TSR Performance-Based Restricted Stock Units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of vesting of target shares upon performance achieved												200.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = ter_TotalShareholderReturnPerformanceBasedRestrictedStockUnitsMember / us-gaap_RangeAxis = us-gaap_MaximumMember
TSR Performance-Based Restricted Stock Units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of vesting of target shares upon performance achieved												0.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = ter_TotalShareholderReturnPerformanceBasedRestrictedStockUnitsMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares available for grant								5,300,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant / us-gaap_AwardTypeAxis = ter_EmployeeStockPurchasePlanMember
Twenty Zero Six Incentive Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award
Employee Stock Purchase Plan to increase the number of shares issuable													10,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized / us-gaap_PlanNameAxis = ter_TwentyZeroSixIncentiveCompensationPlanMember
Aggregate number of shares issuable													32,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_PlanNameAxis = ter_TwentyZeroSixIncentiveCompensationPlanMember
1996 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Employee Stock Purchase Plan to increase the number of shares issuable													5,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized / us-gaap_PlanNameAxis = ter_NineteenNinetySixEmployeeStockPurchasePlanMember
Aggregate number of shares issuable													30,400,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_PlanNameAxis = ter_NineteenNinetySixEmployeeStockPurchasePlanMember

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