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Schedule of Estimated Fair Value Employees Purchase Right Using Black Scholes Option Pricing Mode (Detail) (Stock Purchase Rights)
12 Months Ended
Dec. 31, 2012
Stock Purchase Rights
 
Share-based Compensation Arrangement by Share-based Payment Award  
Expected life (years) 6 months
Risk-free interest rate 0.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= ter_StockPurchaseRightsMember
Volatility-historical 42.70%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= ter_StockPurchaseRightsMember
Dividend yield 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= ter_StockPurchaseRightsMember