XML 53 R41.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Income Taxes (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2017 | Jan. 01, 2017 | Sep. 30, 2018 | Oct. 01, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Income tax benefit | $ 623 | $ (10,358) |  |
Effective tax rate (as a percent) | (1.40%) |  |  |
Deferred tax benefit from tax reform remeasurement | $ 10,100 |  |  |
Effective income tax rate excluding revaluation of deferred taxes (as a percent) | 20.90% |  |  |
Effective income tax rate excluding excess tax benefit and TCJA impacts (as a percent) | 28.00% | 32.80% |  |
Liability for uncertain tax positions | $ 9,400 |  |  | $ 9,300
Period during which unrecognized tax benefits would affect the effective tax rate | 12 months |  |  |
Accounting Standards Update 2016-09 |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Excess tax benefit | $ 3,200 |  |  | $ 1,800
Scenario, Forecast |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Statutory federal tax rate |  |  | 24.50% |

X
- Definition Effective Income Tax Rate Reconciliation, Excluding Revaluation Of Deferred Taxes, Percent + References No definition available. + Details
Name: | ttek_EffectiveIncomeTaxRateReconciliationExcludingRevaluationOfDeferredTaxesPercent
Namespace Prefix: | ttek_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Effective Income Tax Rate Reconciliation, Excluding Share-based Compensation Excess Tax Benefit And Tax Cuts And Jobs Act Impacts, Percent + References No definition available. + Details
Name: | ttek_EffectiveIncomeTaxRateReconciliationExcludingSharebasedCompensationExcessTaxBenefitAndTaxCutsAndJobsActImpactsPercent
Namespace Prefix: | ttek_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount + References No definition available. + Details
Name: | ttek_EffectiveIncomeTaxRateReconciliationSharebasedCompensationExcessTaxBenefitAmount
Namespace Prefix: | ttek_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount recognized for uncertainty in income taxes. + References No definition available. + Details
Name: | ttek_LiabilityForUncertainTaxPositionsCurrentAndNoncurrent
Namespace Prefix: | ttek_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit) + References No definition available. + Details
Name: | ttek_TaxCutsandJobsActof2017IncompleteAccountingChangeinTaxRateProvisionalIncomeTaxExpenseBenefit
Namespace Prefix: | ttek_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The period over which the unrecognized tax benefits are expected to affect the effective tax rate. + References No definition available. + Details
Name: | ttek_UnrecognizedTaxBenefitsPeriodToAffectTaxRate
Namespace Prefix: | ttek_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)(2)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateContinuingOperations
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a),(b) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
Name: | us-gaap_IncomeTaxExpenseBenefit
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201609Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |