Investments in Marketable Securities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified
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Dec. 31, 2014
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Dec. 31, 2013
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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Total cash equivalents and marketable securities |
$ 54,373us-gaap_AvailableForSaleSecurities |
$ 89,292us-gaap_AvailableForSaleSecurities |
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring |
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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Total cash equivalents and marketable securities |
22,926us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
42,436us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Fair Value, Inputs, Level 1 | US Treasury and Government | Fair Value, Measurements, Recurring |
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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Total cash equivalents and marketable securities |
22,685us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember |
37,029us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember |
Fair Value, Inputs, Level 1 | Certificates of Deposit | Fair Value, Measurements, Recurring |
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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Total cash equivalents and marketable securities |
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5,000us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CertificatesOfDepositMember |
Fair Value, Inputs, Level 1 | Accrued Interest | Fair Value, Measurements, Recurring |
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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Total cash equivalents and marketable securities |
241us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = trgt_AccruedInterestMember |
407us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = trgt_AccruedInterestMember |
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring |
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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Total cash equivalents and marketable securities |
31,447us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
46,856us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Fair Value, Inputs, Level 2 | Corporate Debt Securities | Fair Value, Measurements, Recurring |
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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Total cash equivalents and marketable securities |
30,372us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember |
43,347us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember |
Fair Value, Inputs, Level 2 | Municipal Bonds | Fair Value, Measurements, Recurring |
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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Total cash equivalents and marketable securities |
$ 1,075us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember |
$ 3,509us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember |