XML 68 R56.htm IDEA: XBRL DOCUMENT
v3.21.2

Income Taxes - Narrative (Details) - USD ($) $ in Millions | 9 Months Ended |
--- | --- | ---
Jun. 27, 2021 | Jun. 28, 2020 | Sep. 27, 2020
Income Tax Disclosure [Abstract] |  |  |
Effective tax rate | 20.40% | 21.20% |
Reduction in income tax expense due to excess tax benefits on share-based payments | $ 8.7 | $ 7.0 |
Effective tax rate, excluding excess tax benefits on share-based payments | 25.00% | 25.40% |
Liability for uncertain tax positions | $ 12.8 |  | $ 9.7

X
- Definition Effective Income Tax Rate Reconciliation, Excluding Excess Tax Benefits On Share-Based Payments + References No definition available. + Details
Name: | ttek_EffectiveIncomeTaxRateReconciliationExcludingExcessTaxBenefitsOnShareBasedPayments
Namespace Prefix: | ttek_
Data Type: | dtr-types:percentItemType
Balance Type: | na
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 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/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32687-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateContinuingOperations
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to expense for award under share-based payment arrangement. Excludes expense determined to be nondeductible upon grant or after for award under share-based payment arrangement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 740 -Section 35 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=120384911&loc=d3e23163-113944 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_IncomeTaxDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration