XML 76 R62.htm IDEA: XBRL DOCUMENT
v3.22.2.2

Acquisitions - Narrative (Details) £ / shares in Units, $ in Thousands, £ in Millions, $ in Millions |  | 3 Months Ended | 6 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | ---
Sep. 23, 2022 employee £ / shares | Jan. 31, 2023 GBP (£) | Sep. 27, 2020 USD ($) | Mar. 29, 2020 USD ($) | Mar. 31, 2019 USD ($) | Apr. 01, 2018 AUD ($) | Oct. 02, 2022 USD ($) acquisition | Oct. 03, 2021 USD ($) employee | Sep. 27, 2020 USD ($) acquisition | Sep. 27, 2020 AUD ($) acquisition | Sep. 29, 2019 USD ($) | Sep. 29, 2019 AUD ($) | Sep. 30, 2018 USD ($) | Sep. 30, 2018 AUD ($) | Sep. 27, 2020 AUD ($)
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number Of Acquisitions | acquisition |  |  |  |  |  |  | 4 |  |  |  |  |  |  |  |
Contingent earn-out liability |  |  |  |  |  |  | $ 65,600 |  |  |  |  |  |  |  |
Fair value adjustments to contingent consideration liabilities |  |  |  |  |  |  | $ (329) | $ 3,273 | $ 14,971 |  |  |  |  |  |
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] |  |  |  |  |  |  | Foreign currency translation adjustments, net of tax | Foreign currency translation adjustments, net of tax | Foreign currency translation adjustments, net of tax | Foreign currency translation adjustments, net of tax |  |  |  |  |
Interest expense | Contingent consideration |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] |  |  |  |  |  |  | Interest Expense | Interest Expense | Interest Expense | Interest Expense |  |  |  |  |
Operating income | Contingent consideration |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] |  |  |  |  |  |  | Income from operations | Income from operations | Income from operations | Income from operations |  |  |  |  |
Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Earn-out period |  |  |  |  |  |  | 3 years |  |  |  |  |  |  |  |
Significant unobservable input, earn-out period |  |  |  |  |  |  | 3 years |  |  |  |  |  |  |  |
Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Earn-out period |  |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |
Significant unobservable input, earn-out period |  |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |
Existing customer contracts | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Useful life of intangible assets |  |  |  |  |  |  | 1 year |  |  |  |  |  |  |  |
Existing customer contracts | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Useful life of intangible assets |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |
Technology and trade names | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Useful life of intangible assets |  |  |  |  |  |  | 3 years |  |  |  |  |  |  |  |
Technology and trade names | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Useful life of intangible assets |  |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |
RPS Group plc |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Pence per share expected to be acquired | £ / shares | £ 2.22 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of employees | employee | 5,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
RPS Group plc | Forecast | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of outstanding shares expected to be acquired |  | 100.00% |  |  |  |  |  |  |  |  |  |  |  |  |
Expected consideration received upon closing of acquisition | £ |  | £ 636 |  |  |  |  |  |  |  |  |  |  |  |  |
Business acquisitions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair value of acquisition purchase price |  |  |  |  |  |  | $ 88,300 | $ 151,700 | $ 88,600 |  |  |  |  |  |
Initial cash payments |  |  |  |  |  |  | 44,000 | 101,400 | 71,400 |  |  |  |  |  |
Payables related to estimated post-closing adjustments |  |  |  |  |  |  | (2,500) |  | 700 |  |  |  |  |  |
Promissory note |  |  |  |  |  |  | 15,500 |  |  |  |  |  |  |  |
Contingent earn-out liability |  |  | $ 16,500 |  |  |  | 31,300 | 50,300 | 16,500 |  |  |  |  |  |
Aggregate maximum of contingent consideration |  |  | 28,000 |  |  |  | 47,000 | $ 74,000 | $ 28,000 |  |  |  |  |  |
Earn-out period |  |  |  |  |  |  |  |  | 3 years | 3 years |  |  |  |  |
Number of acquisitions | acquisition |  |  |  |  |  |  |  |  | 2 | 2 |  |  |  |  |
Business acquisitions | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Earn-out period |  |  |  |  |  |  |  | 3 years |  |  |  |  |  |  |
Business acquisitions | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Earn-out period |  |  |  |  |  |  |  | 4 years |  |  |  |  |  |  |
Hoare Lea |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of employees | employee |  |  |  |  |  |  |  | 900 |  |  |  |  |  |  |
NDY |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Contingent earn-out liability |  |  | 1,800 |  |  | $ 9.4 |  |  | $ 1,800 |  |  |  |  |  | $ 2.6
Aggregate maximum of contingent consideration |  |  |  |  |  | $ 25.0 |  |  |  |  |  |  |  |  |
Earn-out period |  |  |  |  |  | 3 years |  |  |  |  |  |  |  |  |
Fair value adjustments to contingent consideration liabilities |  |  |  |  |  |  |  |  | 3,700 | $ 5.2 | $ (5,400) | $ (7.9) | $ (2,100) | $ (3.0) |
Maximum contingent consideration, year one |  |  |  |  |  | $ 7.4 |  |  |  |  |  |  |  |  |
Maximum contingent consideration, year two |  |  |  |  |  | 8.8 |  |  |  |  |  |  |  |  |
Maximum contingent consideration, year three |  |  |  |  |  | $ 8.8 |  |  |  |  |  |  |  |  |
Percentage of maximum potential earn-out |  |  |  |  |  | 38.00% |  |  |  |  |  |  |  |  |
EGT |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Contingent earn-out liability |  |  | 7,500 |  | $ 21,100 |  |  |  | 7,500 |  |  |  |  |  |
Aggregate maximum of contingent consideration |  |  |  |  | $ 25,000 |  |  |  |  |  |  |  |  |  |
Earn-out period |  |  |  |  | 3 years |  |  |  |  |  |  |  |  |  |
Fair value adjustments to contingent consideration liabilities |  |  |  |  |  |  |  |  | 4,700 |  |  |  |  |  |
Maximum contingent consideration, year one |  |  |  |  | $ 8,500 |  |  |  |  |  |  |  |  |  |
Maximum contingent consideration, year two |  |  |  |  | 9,000 |  |  |  |  |  |  |  |  |  |
Maximum contingent consideration, year three |  |  |  |  | $ 7,500 |  |  |  |  |  |  |  |  |  |
Percentage of maximum potential earn-out |  |  |  |  | 84.00% |  |  |  |  |  |  |  |  |  |
SEG |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Contingent earn-out liability |  |  | 8,100 | $ 11,300 |  |  |  |  | $ 8,100 |  |  |  |  |  |
Aggregate maximum of contingent consideration |  |  |  | $ 20,000 |  |  |  |  |  |  |  |  |  |  |
Earn-out period |  |  |  | 3 years |  |  |  |  |  |  |  |  |  |  |
Fair value adjustments to contingent consideration liabilities |  |  | $ 3,400 |  |  |  |  |  |  |  |  |  |  |  |
Maximum contingent consideration, year one |  |  |  | $ 5,000 |  |  |  |  |  |  |  |  |  |  |
Maximum contingent consideration, year two |  |  |  | 7,000 |  |  |  |  |  |  |  |  |  |  |
Maximum contingent consideration, year three |  |  |  | $ 8,000 |  |  |  |  |  |  |  |  |  |  |
Percentage of maximum potential earn-out |  |  |  | 57.00% |  |  |  |  |  |  |  |  |  |  |
All acquisitions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate maximum of contingent consideration |  |  |  |  |  |  | $ 120,900 |  |  |  |  |  |  |  |

X
- Definition Represents the earn out period for operating income projection used for fair value measurement. + References No definition available. + Details
Name: | ttek_BusinessAcquisitionEarnOutPeriodForOperatingIncomeProjectionsUsedInFairValueMeasurement
Namespace Prefix: | ttek_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Business Combination, Consideration Transferred, Working Capital Adjustments + References No definition available. + Details
Name: | ttek_BusinessCombinationConsiderationTransferredWorkingCapitalAdjustments
Namespace Prefix: | ttek_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Business Combination, Contingent Consideration Arrangements, Earn Out Period + References No definition available. + Details
Name: | ttek_BusinessCombinationContingentConsiderationArrangementsEarnOutPeriod
Namespace Prefix: | ttek_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Business Combination, Contingent Consideration Arrangements, Percentage Of Maximum Potential Earn-out + References No definition available. + Details
Name: | ttek_BusinessCombinationContingentConsiderationArrangementsPercentageOfMaximumPotentialEarnOut
Namespace Prefix: | ttek_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High, Year One + References No definition available. + Details
Name: | ttek_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHighYearOne
Namespace Prefix: | ttek_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High, Year Three + References No definition available. + Details
Name: | ttek_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHighYearThree
Namespace Prefix: | ttek_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High, Year Two + References No definition available. + Details
Name: | ttek_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHighYearTwo
Namespace Prefix: | ttek_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Business Combination, Price of Acquisition, Expected + References No definition available. + Details
Name: | ttek_BusinessCombinationPriceOfAcquisitionExpected
Namespace Prefix: | ttek_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Expected Price Per Share Acquired + References No definition available. + Details
Name: | ttek_ExpectedPricePerShareAcquired
Namespace Prefix: | ttek_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition The amount of fair value adjustments to contingent consideration during the reporting period. + References No definition available. + Details
Name: | ttek_FairValueAdjustmentsToContingentConsideration
Namespace Prefix: | ttek_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Number Of Acquisitions + References No definition available. + Details
Name: | ttek_NumberOfAcquisitions
Namespace Prefix: | ttek_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the number of employees acquired in the acquisition. + References No definition available. + Details
Name: | ttek_NumberOfEmployeesAcquiredInAcquisition
Namespace Prefix: | ttek_
Data Type: | xbrli:integerItemType
Balance Type: | na
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_BusinessAcquisitionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of voting equity interests acquired at the acquisition date in the business combination. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463 + Details
Name: | us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6613-128477 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6578-128477 + Details
Name: | us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of liabilities incurred by the acquirer as part of consideration transferred in a business combination. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6578-128477 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 25 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6405-128476 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6613-128477 + Details
Name: | us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479 + Details
Name: | us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of liability recognized arising from contingent consideration in a business combination. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 35 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=116859824&loc=d3e6819-128478 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 25 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476 + Details
Name: | us-gaap_BusinessCombinationContingentConsiderationLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Indicates line item in statement in which net income is reported that includes gain (loss) from liability measured at fair value using unobservable input (level 3). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueRecurringBasisUnobservableInputReconciliationLiabilityGainLossStatementOfIncomeExtensibleList
Namespace Prefix: | us-gaap_
Data Type: | enum2:enumerationSetItemType
Balance Type: | na
Period Type: | duration

X
- Definition Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of businesses acquired by the entity during the period. + References No definition available. + Details
Name: | us-gaap_NumberOfBusinessesAcquired
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3213-108585 + Details
Name: | us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=us-gaap_InterestExpenseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByLiabilityClassAxis=ttek_ContingentConsiderationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=us-gaap_OperatingIncomeLossMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CustomerContractsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_TradeNamesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=ttek_RPSGroupPlcMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=ttek_HoareLeaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=ttek_NormanDisneyAndYoungMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=ttek_EGlobalTechMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=ttek_SegueTechnologiesIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=ttek_AllAcquisitionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |