$TTEK
TETRA TECH INC Stock $ttek

$ttek Overview Financials Valuation SEC Filings Company Website

2020 Q3 Form 10-K Financial Statement

#000083164120000154 Filed on November 23, 2020

Income Statement

Concept	2020 Q3	2019 Q3	2019 Q2
Revenue	$753.4M	$841.5M	$825.8M
YoY Change	-10.47%	13.82%	17.93%
Cost Of Revenue	$464.4M	$532.7M	$505.2M
YoY Change	-12.82%	15.6%	14.45%
Gross Profit	$125.4M	$95.00M	$118.0M
YoY Change	32.0%	-13.32%	29.05%
Gross Profit Margin	16.65%	11.29%	14.29%
Selling, General & Admin	$56.30M	$55.20M	$53.10M
YoY Change	1.99%	2.41%	13.46%
% of Gross Profit	44.9%	58.11%	45.0%
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$5.500M	$7.500M	$4.200M
YoY Change	-26.67%	53.06%	-17.65%
% of Gross Profit	4.39%	7.89%	3.56%
Operating Expenses	$42.90M	$56.20M	$53.20M
YoY Change	-23.67%	3.88%	9.24%
Operating Profit	$66.74M	$20.67M	$64.84M
YoY Change	222.94%	-52.26%	51.8%
Interest Expense	-$2.700M	-$4.000M	-$3.500M
YoY Change	-32.5%	-6.98%	-14.63%
% of Operating Profit	-4.05%	-19.36%	-5.4%
Other Income/Expense, Net
YoY Change
Pretax Income	$64.00M	$16.60M	$61.30M
YoY Change	285.54%	-67.55%	58.7%
Income Tax	$19.40M	$5.100M	$12.04M
% Of Pretax Income	30.31%	30.72%	19.65%
Net Earnings	$44.70M	$11.50M	$49.25M
YoY Change	288.7%	-65.51%	71.33%
Net Earnings / Revenue	5.93%	1.37%	5.96%
Basic Earnings Per Share	$0.83	$0.21	$0.90
Diluted Earnings Per Share	$0.82	$0.21	$0.88
COMMON SHARES
Basic Shares Outstanding	53.84M shares	54.62M shares	54.82M shares
Diluted Shares Outstanding	54.60M shares	55.62M shares	55.77M shares

Balance Sheet

Concept	2020 Q3	2019 Q3	2019 Q2
SHORT-TERM ASSETS
Cash & Short-Term Investments	$157.5M	$120.7M	$111.2M
YoY Change	30.49%	-43.6%	-45.28%
Cash & Equivalents	$157.5M	$120.7M	$111.2M
Short-Term Investments
Other Short-Term Assets	$81.10M	$62.20M	$123.8M
YoY Change	30.39%	3.49%	90.17%
Inventory
Prepaid Expenses
Receivables	$649.0M	$768.7M	$729.0M
Other Receivables	$19.50M	$13.90M	$6.700M
Total Short-Term Assets	$999.8M	$1.080B	$1.116B
YoY Change	-7.41%	2.8%	-2.91%
LONG-TERM ASSETS
Property, Plant & Equipment	$35.51M	$39.44M	$40.07M
YoY Change	-9.97%	-8.87%	-27.79%
Goodwill	$993.5M	$924.8M	$851.6M
YoY Change	7.43%	15.77%	5.18%
Intangibles		$16.44M	$10.44M
YoY Change		1.97%	-49.93%
Long-Term Investments	$7.332M	$6.873M	$7.655M
YoY Change	6.68%	103.95%	141.71%
Other Assets	$57.05M	$51.66M	$39.59M
YoY Change	10.43%	32.99%	12.79%
Total Long-Term Assets	$1.379B	$1.068B	$979.9M
YoY Change	29.15%	17.44%	5.04%
TOTAL ASSETS
Total Short-Term Assets	$999.8M	$1.080B	$1.116B
Total Long-Term Assets	$1.379B	$1.068B	$979.9M
Total Assets	$2.379B	$2.147B	$2.096B
YoY Change	10.76%	9.59%	0.65%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$111.8M	$206.6M	$179.2M
YoY Change	-45.89%	28.95%	15.42%
Accrued Expenses	$269.5M	$203.4M	$160.8M
YoY Change	32.5%	41.15%	14.53%
Deferred Revenue	$171.9M	$165.6M	$147.5M
YoY Change	3.8%	15.59%
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due	$49.26M	$12.60M	$12.50M
YoY Change	290.98%	-32.62%	-19.35%
Total Short-Term Liabilities	$793.5M	$770.0M	$646.9M
YoY Change	3.05%	24.57%	15.52%
LONG-TERM LIABILITIES
Long-Term Debt	$242.4M	$263.9M	$324.1M
YoY Change	-8.16%	-37.01%	-30.08%
Other Long-Term Liabilities	$80.59M	$83.07M	$53.93M
YoY Change	-2.99%	43.99%	-1.65%
Total Long-Term Liabilities	$323.0M	$347.0M	$53.93M
YoY Change	-6.92%	501.47%	-1.65%
TOTAL LIABILITIES
Total Short-Term Liabilities	$793.5M	$770.0M	$646.9M
Total Long-Term Liabilities	$323.0M	$347.0M	$53.93M
Total Liabilities	$1.116B	$1.117B	$700.8M
YoY Change	-0.05%	65.28%	13.98%
SHAREHOLDERS EQUITY
Retained Earnings	$1.199B	$1.071B	$1.068B
YoY Change	11.89%	13.36%	19.16%
Common Stock	$538.0K	$78.68M	$94.84M
YoY Change	-99.32%	-47.32%	-41.44%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$1.037B	$989.3M	$1.016B
YoY Change
Total Liabilities & Shareholders Equity	$2.379B	$2.147B	$2.096B
YoY Change	10.76%	9.59%	0.65%

Cashflow Statement

Concept	2020 Q3	2019 Q3	2019 Q2
OPERATING ACTIVITIES
Net Income	$44.70M	$11.50M	$49.25M
YoY Change	288.7%	-65.51%	71.33%
Depreciation, Depletion And Amortization	$5.500M	$7.500M	$4.200M
YoY Change	-26.67%	53.06%	-17.65%
Cash From Operating Activities	$67.90M	$95.10M	$14.20M
YoY Change	-28.6%	117.12%	-82.53%
INVESTING ACTIVITIES
Capital Expenditures	-$2.800M	-$6.200M	-$2.800M
YoY Change	-54.84%	264.71%	12.0%
Acquisitions
YoY Change
Other Investing Activities	-$39.50M	-$48.80M	-$38.50M
YoY Change	-19.06%	-234.44%	-14.82%
Cash From Investing Activities	-$42.30M	-$55.00M	-$41.30M
YoY Change	-23.09%	-259.42%	-13.42%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-10.40M	-87.80M	63.40M
YoY Change	-88.15%	39.37%	-2981.82%
NET CHANGE
Cash From Operating Activities	67.90M	95.10M	14.20M
Cash From Investing Activities	-42.30M	-55.00M	-41.30M
Cash From Financing Activities	-10.40M	-87.80M	63.40M
Net Change In Cash	15.20M	-47.70M	36.30M
YoY Change	-131.87%	-411.76%	15.61%
FREE CASH FLOW
Cash From Operating Activities	$67.90M	$95.10M	$14.20M
Capital Expenditures	-$2.800M	-$6.200M	-$2.800M
Free Cash Flow	$70.70M	$101.3M	$17.00M
YoY Change	-30.21%	122.64%	-79.71%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2020	dei	Entity Central Index Key EntityCentralIndexKey	0000831641
CY2020	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2020
CY2020	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2020	dei	Amendment Flag AmendmentFlag	false
CY2020Q3	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1	P1Y
CY2020Q3	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due Current OperatingLeasesFutureMinimumPaymentsDueCurrent	108800000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due In Two Years OperatingLeasesFutureMinimumPaymentsDueInTwoYears	66400000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due In Three Years OperatingLeasesFutureMinimumPaymentsDueInThreeYears	51400000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due In Four Years OperatingLeasesFutureMinimumPaymentsDueInFourYears	36500000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due In Five Years OperatingLeasesFutureMinimumPaymentsDueInFiveYears	25800000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due Thereafter OperatingLeasesFutureMinimumPaymentsDueThereafter	54600000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due OperatingLeasesFutureMinimumPaymentsDue	343500000	USD
CY2020	dei	Document Type DocumentType	10-K
CY2020	dei	Document Annual Report DocumentAnnualReport	true
CY2020	dei	Document Period End Date DocumentPeriodEndDate	2020-09-27
CY2020	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--09-27
CY2020	dei	Document Transition Report DocumentTransitionReport	false
CY2020	dei	Entity File Number EntityFileNumber	0-19655
CY2020	dei	Entity Registrant Name EntityRegistrantName	TETRA TECH, INC.
CY2020	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
CY2020	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	95-4148514
CY2020	dei	Entity Address Address Line1 EntityAddressAddressLine1	3475 East Foothill Boulevard
CY2020	dei	Entity Address City Or Town EntityAddressCityOrTown	Pasadena
CY2020	dei	Entity Address State Or Province EntityAddressStateOrProvince	CA
CY2020	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	91107
CY2020	dei	City Area Code CityAreaCode	626
CY2020	dei	Local Phone Number LocalPhoneNumber	351-4664
CY2020	dei	Security12b Title Security12bTitle	Common Stock, $0.01 par value
CY2020	dei	Trading Symbol TradingSymbol	TTEK
CY2020	dei	Security Exchange Name SecurityExchangeName	NASDAQ
CY2020	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2020	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2020	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2020	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2020	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2020	dei	Entity Small Business EntitySmallBusiness	false
CY2020	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2020	dei	Icfr Auditor Attestation Flag IcfrAuditorAttestationFlag	true
CY2020	dei	Entity Shell Company EntityShellCompany	false
CY2020Q1	dei	Entity Public Float EntityPublicFloat	3600000000	USD
CY2020Q4	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	53777381	shares
CY2020Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	157515000	USD
CY2019Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	120732000	USD
CY2020Q3	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	649035000	USD
CY2019Q3	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	768720000	USD
CY2020Q3	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	92632000	USD
CY2019Q3	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	114324000	USD
CY2020Q3	us-gaap	Prepaid Expense And Other Assets Current PrepaidExpenseAndOtherAssetsCurrent	81094000	USD
CY2019Q3	us-gaap	Prepaid Expense And Other Assets Current PrepaidExpenseAndOtherAssetsCurrent	62196000	USD
CY2020Q3	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	19509000	USD
CY2019Q3	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	13820000	USD
CY2020Q3	us-gaap	Assets Current AssetsCurrent	999785000	USD
CY2019Q3	us-gaap	Assets Current AssetsCurrent	1079792000	USD
CY2020Q3	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	35507000	USD
CY2019Q3	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	39441000	USD
CY2020Q3	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	239396000	USD
CY2020Q3	us-gaap	Equity Method Investments EquityMethodInvestments	7332000	USD
CY2019Q3	us-gaap	Equity Method Investments EquityMethodInvestments	6873000	USD
CY2020Q3	us-gaap	Goodwill Goodwill	993498000	USD
CY2019Q3	us-gaap	Goodwill Goodwill	924820000	USD
CY2020Q3	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	13943000	USD
CY2019Q3	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	16440000	USD
CY2020Q3	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	32052000	USD
CY2019Q3	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	28385000	USD
CY2020Q3	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	57045000	USD
CY2019Q3	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	51657000	USD
CY2020Q3	us-gaap	Assets Assets	2378558000	USD
CY2019Q3	us-gaap	Assets Assets	2147408000	USD
CY2020Q3	us-gaap	Accounts Payable Current AccountsPayableCurrent	111804000	USD
CY2019Q3	us-gaap	Accounts Payable Current AccountsPayableCurrent	206609000	USD
CY2020Q3	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	199801000	USD
CY2019Q3	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	203384000	USD
CY2020Q3	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	171905000	USD
CY2019Q3	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	165611000	USD
CY2020Q3	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	69650000	USD
CY2020Q3	us-gaap	Debt Current DebtCurrent	49264000	USD
CY2019Q3	us-gaap	Debt Current DebtCurrent	12500000	USD
CY2020Q3	us-gaap	Business Combination Contingent Consideration Liability Current BusinessCombinationContingentConsiderationLiabilityCurrent	16142000	USD
CY2019Q3	us-gaap	Business Combination Contingent Consideration Liability Current BusinessCombinationContingentConsiderationLiabilityCurrent	24977000	USD
CY2020Q3	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	174890000	USD
CY2019Q3	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	156873000	USD
CY2020Q3	us-gaap	Liabilities Current LiabilitiesCurrent	793456000	USD
CY2019Q3	us-gaap	Liabilities Current LiabilitiesCurrent	769954000	USD
CY2020Q3	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	16316000	USD
CY2019Q3	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	12971000	USD
CY2020Q3	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	242395000	USD
CY2019Q3	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	263934000	USD
CY2020Q3	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	191955000	USD
CY2020Q3	us-gaap	Business Combination Contingent Consideration Liability Noncurrent BusinessCombinationContingentConsiderationLiabilityNoncurrent	16475000	USD
CY2019Q3	us-gaap	Business Combination Contingent Consideration Liability Noncurrent BusinessCombinationContingentConsiderationLiabilityNoncurrent	28015000	USD
CY2020Q3	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	80588000	USD
CY2019Q3	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	83070000	USD
CY2020Q3	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2019Q3	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2020Q3	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	2000000	shares
CY2019Q3	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	2000000	shares
CY2019Q3	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0.01
CY2020Q3	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0.01
CY2019Q3	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2019Q3	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2020Q3	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2020Q3	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2020Q3	us-gaap	Preferred Stock Value PreferredStockValue	0	USD
CY2019Q3	us-gaap	Preferred Stock Value PreferredStockValue	0	USD
CY2019Q3	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	150000000	shares
CY2020Q3	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	150000000	shares
CY2020Q3	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
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CY2020Q3	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	53797000	shares
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CY2019Q3	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	54565000	shares
CY2019Q3	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	54565000	shares
CY2020Q3	us-gaap	Common Stock Value CommonStockValue	538000	USD
CY2019Q3	us-gaap	Common Stock Value CommonStockValue	546000	USD
CY2020Q3	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	0	USD
CY2019Q3	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	78132000	USD
CY2020Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-161786000	USD
CY2019Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-160584000	USD
CY2020Q3	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1198567000	USD
CY2019Q3	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1071192000	USD
CY2020Q3	us-gaap	Stockholders Equity StockholdersEquity	1037319000	USD
CY2019Q3	us-gaap	Stockholders Equity StockholdersEquity	989286000	USD
CY2020Q3	us-gaap	Minority Interest MinorityInterest	54000	USD
CY2019Q3	us-gaap	Minority Interest MinorityInterest	178000	USD
CY2020Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1037373000	USD
CY2019Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	989464000	USD
CY2020Q3	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	2378558000	USD
CY2019Q3	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	2147408000	USD
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2994891000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3107348000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2964148000	USD
CY2020	us-gaap	Gross Profit GrossProfit	446535000	USD
CY2019	us-gaap	Gross Profit GrossProfit	408183000	USD
CY2018	us-gaap	Gross Profit GrossProfit	384458000	USD
CY2020	ttek	Selling General And Administrative Expenses Including Depreciation And Amortization Of Intangible Assets SellingGeneralAndAdministrativeExpensesIncludingDepreciationAndAmortizationOfIntangibleAssets	204615000	USD
CY2019	ttek	Selling General And Administrative Expenses Including Depreciation And Amortization Of Intangible Assets SellingGeneralAndAdministrativeExpensesIncludingDepreciationAndAmortizationOfIntangibleAssets	200230000	USD
CY2018	ttek	Selling General And Administrative Expenses Including Depreciation And Amortization Of Intangible Assets SellingGeneralAndAdministrativeExpensesIncludingDepreciationAndAmortizationOfIntangibleAssets	190120000	USD
CY2020	ttek	Business Combination Acquisition And Integration Related Costs BusinessCombinationAcquisitionAndIntegrationRelatedCosts	0	USD
CY2019	ttek	Business Combination Acquisition And Integration Related Costs BusinessCombinationAcquisitionAndIntegrationRelatedCosts	10351000	USD
CY2018	ttek	Business Combination Acquisition And Integration Related Costs BusinessCombinationAcquisitionAndIntegrationRelatedCosts	0	USD
CY2020	ttek	Fair Value Adjustments To Contingent Consideration FairValueAdjustmentsToContingentConsideration	14971000	USD
CY2019	ttek	Fair Value Adjustments To Contingent Consideration FairValueAdjustmentsToContingentConsideration	-1085000	USD
CY2018	ttek	Fair Value Adjustments To Contingent Consideration FairValueAdjustmentsToContingentConsideration	-4252000	USD
CY2020	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	15800000	USD
CY2019	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	7755000	USD
CY2018	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2020	us-gaap	Operating Income Loss OperatingIncomeLoss	241091000	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	188762000	USD
CY2018	us-gaap	Operating Income Loss OperatingIncomeLoss	190086000	USD
CY2020	us-gaap	Investment Income Interest InvestmentIncomeInterest	1375000	USD
CY2019	us-gaap	Investment Income Interest InvestmentIncomeInterest	1732000	USD
CY2018	us-gaap	Investment Income Interest InvestmentIncomeInterest	1824000	USD
CY2020	us-gaap	Interest Expense InterestExpense	14475000	USD
CY2019	us-gaap	Interest Expense InterestExpense	15358000	USD
CY2018	us-gaap	Interest Expense InterestExpense	17348000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	227991000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	175136000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	174562000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	54101000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	16375000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	37605000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	173890000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	158761000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	136957000	USD
CY2020	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	31000	USD
CY2019	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	93000	USD
CY2018	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	74000	USD
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	173859000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	158668000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	136883000	USD
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.21
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.89
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.46
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.16
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.84
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.42
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	54235000	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	54986000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	55670000	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	55022000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	55936000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	56598000	shares
CY2020	us-gaap	Profit Loss ProfitLoss	173890000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	158761000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	136957000	USD
CY2020	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent	3436000	USD
CY2019	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent	-21109000	USD
CY2018	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent	-29656000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax Parent OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent	-4638000	USD
CY2019	us-gaap	Other Comprehensive Income Derivatives Qualifying As Hedges Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPortionAttributableToParent	-12125000	USD
CY2018	us-gaap	Other Comprehensive Income Derivatives Qualifying As Hedges Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPortionAttributableToParent	806000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-1202000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-33234000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-28850000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	1000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	-243000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	64000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	172687000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	125770000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	108043000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	172657000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	125434000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	108033000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	30000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	336000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	10000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	172687000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	125770000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	108043000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	173890000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	158761000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	136957000	USD
CY2020	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	24611000	USD
CY2019	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	28844000	USD
CY2018	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	38636000	USD
CY2020	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	6605000	USD
CY2019	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	4073000	USD
CY2018	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	4008000	USD
CY2020	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	6310000	USD
CY2019	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	4048000	USD
CY2018	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	3440000	USD
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	19424000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	17618000	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	19582000	USD
CY2020	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	565000	USD
CY2019	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	-37615000	USD
CY2018	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	-29360000	USD
CY2020	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	1267000	USD
CY2019	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	16964000	USD
CY2018	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	7167000	USD
CY2020	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	15800000	USD
CY2019	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	7755000	USD
CY2018	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2020	ttek	Fair Value Adjustments To Contingent Consideration FairValueAdjustmentsToContingentConsideration	14971000	USD
CY2019	ttek	Fair Value Adjustments To Contingent Consideration FairValueAdjustmentsToContingentConsideration	-1085000	USD
CY2018	ttek	Fair Value Adjustments To Contingent Consideration FairValueAdjustmentsToContingentConsideration	-4252000	USD
CY2020	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	11066000	USD
CY2019	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	232000	USD
CY2018	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	-1045000	USD
CY2020	ttek	Increase Decrease In Accounts Receivable And Contract With Customer Asset IncreaseDecreaseInAccountsReceivableAndContractWithCustomerAsset	-154748000	USD
CY2019	ttek	Increase Decrease In Accounts Receivable And Contract With Customer Asset IncreaseDecreaseInAccountsReceivableAndContractWithCustomerAsset	10226000	USD
CY2018	ttek	Increase Decrease In Accounts Receivable And Contract With Customer Asset IncreaseDecreaseInAccountsReceivableAndContractWithCustomerAsset	46273000	USD
CY2020	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	11321000	USD
CY2019	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	-2568000	USD
CY2018	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	12638000	USD
CY2020	us-gaap	Increase Decrease In Accounts Payable IncreaseDecreaseInAccountsPayable	-102162000	USD
CY2019	us-gaap	Increase Decrease In Accounts Payable IncreaseDecreaseInAccountsPayable	39011000	USD
CY2018	us-gaap	Increase Decrease In Accounts Payable IncreaseDecreaseInAccountsPayable	-16032000	USD
CY2020	ttek	Increase Decrease In Accrued Compensation IncreaseDecreaseInAccruedCompensation	-8173000	USD
CY2019	ttek	Increase Decrease In Accrued Compensation IncreaseDecreaseInAccruedCompensation	18359000	USD
CY2018	ttek	Increase Decrease In Accrued Compensation IncreaseDecreaseInAccruedCompensation	27492000	USD
CY2020	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	5894000	USD
CY2019	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	-6039000	USD
CY2018	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	15228000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	19460000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-16929000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	24998000	USD
CY2020	us-gaap	Increase Decrease In Income Taxes Payable Net Of Income Taxes Receivable IncreaseDecreaseInIncomeTaxesPayableNetOfIncomeTaxesReceivable	-5192000	USD
CY2019	us-gaap	Increase Decrease In Income Taxes Payable Net Of Income Taxes Receivable IncreaseDecreaseInIncomeTaxesPayableNetOfIncomeTaxesReceivable	-11386000	USD
CY2018	us-gaap	Increase Decrease In Income Taxes Payable Net Of Income Taxes Receivable IncreaseDecreaseInIncomeTaxesPayableNetOfIncomeTaxesReceivable	17596000	USD
CY2020	us-gaap	Payment For Contingent Consideration Liability Operating Activities PaymentForContingentConsiderationLiabilityOperatingActivities	0	USD
CY2019	us-gaap	Payment For Contingent Consideration Liability Operating Activities PaymentForContingentConsiderationLiabilityOperatingActivities	0	USD
CY2018	us-gaap	Payment For Contingent Consideration Liability Operating Activities PaymentForContingentConsiderationLiabilityOperatingActivities	2349000	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	262479000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	208513000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	185733000	USD
CY2020	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	68488000	USD
CY2019	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	84159000	USD
CY2018	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	68256000	USD
CY2020	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	12245000	USD
CY2019	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	16198000	USD
CY2018	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	9726000	USD
CY2020	us-gaap	Proceeds From Divestiture Of Businesses ProceedsFromDivestitureOfBusinesses	17710000	USD
CY2019	us-gaap	Proceeds From Divestiture Of Businesses ProceedsFromDivestitureOfBusinesses	651000	USD
CY2018	us-gaap	Proceeds From Divestiture Of Businesses ProceedsFromDivestitureOfBusinesses	35348000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-63023000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-99706000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-42634000	USD
CY2020	us-gaap	Proceeds From Issuance Of Long Term Debt And Capital Securities Net ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet	344991000	USD
CY2019	us-gaap	Proceeds From Issuance Of Long Term Debt And Capital Securities Net ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet	417262000	USD
CY2018	us-gaap	Proceeds From Issuance Of Long Term Debt And Capital Securities Net ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet	401965000	USD
CY2020	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	331066000	USD
CY2019	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	415491000	USD
CY2018	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	485946000	USD
CY2020	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	117188000	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	100000000	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	75000000	USD
CY2020	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	11166000	USD
CY2019	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	6893000	USD
CY2018	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	8871000	USD
CY2020	us-gaap	Payment For Contingent Consideration Liability Financing Activities PaymentForContingentConsiderationLiabilityFinancingActivities	22900000	USD
CY2019	us-gaap	Payment For Contingent Consideration Liability Financing Activities PaymentForContingentConsiderationLiabilityFinancingActivities	12018000	USD
CY2018	us-gaap	Payment For Contingent Consideration Liability Financing Activities PaymentForContingentConsiderationLiabilityFinancingActivities	1412000	USD
CY2020	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	0	USD
CY2019	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	0	USD
CY2018	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	1737000	USD
CY2020	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	10334000	USD
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	11751000	USD
CY2018	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	13520000	USD
CY2020	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	34743000	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	29674000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	24477000	USD
CY2020	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	1311000	USD
CY2019	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	0	USD
CY2018	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	0	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-163049000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-135063000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-181958000	USD
CY2020	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	207000	USD
CY2019	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-1727000	USD
CY2018	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-4947000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	36614000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-27983000	USD
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-43806000	USD
CY2019Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	120901000	USD
CY2018Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	148884000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	192690000	USD
CY2020Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	157515000	USD
CY2019Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	120901000	USD
CY2018Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	148884000	USD
CY2020	us-gaap	Interest Paid Net InterestPaidNet	13256000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	12310000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	15570000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	136957000	USD
CY2020	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	1400000	USD
CY2019	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	5200000	USD
CY2018	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	2500000	USD
CY2020	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	55039000	USD
CY2019	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	66038000	USD
CY2018	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	49842000	USD
CY2020Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	157515000	USD
CY2019Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	120732000	USD
CY2018Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	146185000	USD
CY2020Q3	us-gaap	Restricted Cash RestrictedCash	0	USD
CY2019Q3	us-gaap	Restricted Cash RestrictedCash	169000	USD
CY2018Q3	us-gaap	Restricted Cash RestrictedCash	2699000	USD
CY2020Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	157515000	USD
CY2019Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	120901000	USD
CY2018Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	148884000	USD
CY2017Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	928624000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-29720000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	806000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	108043000	USD
CY2018	us-gaap	Minority Interest Decrease From Distributions To Noncontrolling Interest Holders MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	52000	USD
CY2018	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.44
CY2018	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	24477000	USD
CY2018	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	19582000	USD
CY2018	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	13511000	USD
CY2018	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	-8871000	USD
CY2018	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	5740000	USD
CY2018	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	75000000	USD
CY2018Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	967100000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	158761000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-20866000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	-12125000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	125770000	USD
CY2019	us-gaap	Minority Interest Decrease From Distributions To Noncontrolling Interest Holders MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	287000	USD
CY2019	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.54
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	29674000	USD
CY2019	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	17618000	USD
CY2019	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	-6893000	USD
CY2019	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	11751000	USD
CY2019	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	6846000	USD
CY2019	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	100000000	USD
CY2019Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	989464000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	173890000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	3435000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	-4638000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	172687000	USD
CY2020	us-gaap	Minority Interest Decrease From Distributions To Noncontrolling Interest Holders MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	154000	USD
CY2020	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.64
CY2020	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	34743000	USD
CY2020	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	19424000	USD
CY2020	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	-11166000	USD
CY2020	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	10334000	USD
CY2020	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	8715000	USD
CY2020	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	117188000	USD
CY2020Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1037373000	USD
CY2020	us-gaap	Nature Of Operations NatureOfOperations	Description of Business <div style="margin-bottom:6pt;margin-top:6pt;text-align:justify;text-indent:36pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">We are a leading global provider of consulting and engineering services that focuses on water, environment, sustainable infrastructure, resource management, energy, and international development. We are a global company that is </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Leading with Science® </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">to provide innovative solutions for our public and private clients. We typically begin at the earliest stage of a project by identifying technical solutions and developing execution plans tailored to our clients’ needs and resources. </span><span style="background-color:#ffffff;color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Our solutions may span the entire life cycle of consulting and engineering projects and include applied science, data analysis, research, engineering, design, construction management, and operations and maintenance.</span></div><div style="margin-bottom:6pt;margin-top:6pt;text-align:justify;text-indent:36pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">We manage our business under two reportable segments. Our Government Services Group (“GSG”) reportable segment primarily includes activities with U.S. government clients (federal, state and local) and all activities with development agencies worldwide. Our Commercial/International Services Group (“CIG”) reportable segment primarily includes activities with U.S. commercial clients and international clients other than development agencies. This alignment allows us to capitalize on our growing market opportunities and enhance the development of high-end consulting and technical solutions to meet our growing client demand. We continue to report the results of the wind-down of our non-core construction activities in the Remediation and Construction Management (“RCM”) reportable segment. Certain reclassifications were made to the prior years to conform to the current-year presentation.</span></div>
CY2020	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	2	segment
CY2020	us-gaap	Fiscal Period FiscalPeriod	<span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Fiscal Year.</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> We report results of operations based on 52 or 53-week periods ending on the Sunday nearest September 30. Fiscal years 2020, 2019 and 2018 each contained 52 weeks.</span>
CY2020	us-gaap	Use Of Estimates UseOfEstimates	<span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Use of Estimates.</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America ("U.S. GAAP") requires us to make estimates and assumptions. These estimates and assumptions affect the amounts reported in our consolidated financial statements and accompanying notes. Although such estimates and assumptions are based on management's best knowledge of current events and actions we may take in the future, actual results could differ materially from those estimates.</span>
CY2020	ttek	Maximum Term Of Original Maturity To Classify An Instrument As Cash Equivalent MaximumTermOfOriginalMaturityToClassifyAnInstrumentAsCashEquivalent	P90D
CY2020	ttek	Unbilled Contracts Receivable Period For Billing And Collection UnbilledContractsReceivablePeriodForBillingAndCollection	P12M
CY2020Q3	us-gaap	Lessee Operating Lease Renewal Term LesseeOperatingLeaseRenewalTerm	P5Y
CY2020	ttek	Number Of Levels Below Reportable Segments For Goodwill Impairment Testing NumberOfLevelsBelowReportableSegmentsForGoodwillImpairmentTesting	1	Level
CY2020	ttek	Number Of Levels Below Reportable Segments For Goodwill Impairment Testing NumberOfLevelsBelowReportableSegmentsForGoodwillImpairmentTesting	1	Level
CY2020	ttek	Concentration Of Credit Risk Number Of Financial Institutions For Investment Exposure ConcentrationOfCreditRiskNumberOfFinancialInstitutionsForInvestmentExposure	1	Institution
CY2020Q3	ttek	Percentage Of Account Receivables Due From Agencies PercentageOfAccountReceivablesDueFromAgencies	0.28
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2994891000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3107348000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2964148000	USD
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2994891000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3107348000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2964148000	USD
CY2020Q3	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	92632000	USD
CY2019Q3	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	114324000	USD
CY2020Q3	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	171905000	USD
CY2019Q3	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	165611000	USD
CY2020Q3	ttek	Contract With Customer Asset Liability Net Current ContractWithCustomerAssetLiabilityNetCurrent	-79273000	USD
CY2019Q3	ttek	Contract With Customer Asset Liability Net Current ContractWithCustomerAssetLiabilityNetCurrent	-51287000	USD
CY2020	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	118000000	USD
CY2019	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	90000000	USD
CY2020	us-gaap	Contract With Customer Liability Cumulative Catch Up Adjustment To Revenue Change In Measure Of Progress ContractWithCustomerLiabilityCumulativeCatchUpAdjustmentToRevenueChangeInMeasureOfProgress	800000	USD
CY2019	us-gaap	Contract With Customer Liability Cumulative Catch Up Adjustment To Revenue Change In Measure Of Progress ContractWithCustomerLiabilityCumulativeCatchUpAdjustmentToRevenueChangeInMeasureOfProgress	800000	USD
CY2020Q3	us-gaap	Provision For Loss On Contracts ProvisionForLossOnContracts	13200000	USD
CY2019Q3	us-gaap	Provision For Loss On Contracts ProvisionForLossOnContracts	11500000	USD
CY2020Q3	ttek	Revenue Recognition Estimated Cost To Complete Related Contracts RevenueRecognitionEstimatedCostToCompleteRelatedContracts	118000000	USD
CY2020Q3	us-gaap	Billed Contract Receivables BilledContractReceivables	402818000	USD
CY2019Q3	us-gaap	Billed Contract Receivables BilledContractReceivables	496985000	USD
CY2020Q3	us-gaap	Unbilled Contracts Receivable UnbilledContractsReceivable	253364000	USD
CY2019Q3	us-gaap	Unbilled Contracts Receivable UnbilledContractsReceivable	282297000	USD
CY2020Q3	us-gaap	Accounts Receivable Gross Current AccountsReceivableGrossCurrent	656182000	USD
CY2019Q3	us-gaap	Accounts Receivable Gross Current AccountsReceivableGrossCurrent	779282000	USD
CY2020Q3	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	7147000	USD
CY2019Q3	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	10562000	USD
CY2020Q3	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	649035000	USD
CY2019Q3	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	768720000	USD
CY2020	ttek	Unbilled Contracts Receivable Period For Billing And Collection UnbilledContractsReceivablePeriodForBillingAndCollection	P12M
CY2020Q3	ttek	Government Contract Receivable Unbilled Amounts Related To Claims And Requests For Equitable Adjustment On Contract GovernmentContractReceivableUnbilledAmountsRelatedToClaimsAndRequestsForEquitableAdjustmentOnContract	14000000	USD
CY2019Q3	ttek	Government Contract Receivable Unbilled Amounts Related To Claims And Requests For Equitable Adjustment On Contract GovernmentContractReceivableUnbilledAmountsRelatedToClaimsAndRequestsForEquitableAdjustmentOnContract	15000000	USD
CY2020Q3	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	3200000000	USD
CY2020Q3	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	1846527000	USD
CY2020Q3	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	1372446000	USD
CY2020Q3	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	3218973000	USD
CY2020	ttek	Revenue Remaining Performance Obligation Termination Notice Period One RevenueRemainingPerformanceObligationTerminationNoticePeriodOne	P30D
CY2020	ttek	Revenue Remaining Performance Obligation Termination Notice Period Two RevenueRemainingPerformanceObligationTerminationNoticePeriodTwo	P60Y
CY2020	ttek	Revenue Remaining Performance Obligation Termination Notice Period Three RevenueRemainingPerformanceObligationTerminationNoticePeriodThree	P90D
CY2018Q4	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	200000000	USD
CY2018Q3	us-gaap	Stock Repurchase Program Remaining Authorized Repurchase Amount1 StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1	25000000	USD
CY2020Q1	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	200000000	USD
CY2020Q3	us-gaap	Stock Repurchase Program Remaining Authorized Repurchase Amount1 StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1	207800000	USD
CY2019	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	1562521	shares
CY2020	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	800000	USD
CY2019	ttek	Shares Repurchased Average Price Per Share SharesRepurchasedAveragePricePerShare	64.00
CY2019	us-gaap	Stock Repurchased During Period Value StockRepurchasedDuringPeriodValue	100000000	USD
CY2019Q4	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.15
CY2019Q4	us-gaap	Dividends Dividends	8190000	USD
CY2020Q1	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.15
CY2020Q1	us-gaap	Dividends Dividends	8225000	USD
CY2020Q2	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.17
CY2020Q2	us-gaap	Dividends Dividends	9175000	USD
CY2020Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.17
CY2020Q3	us-gaap	Dividends Dividends	9153000	USD
CY2020	us-gaap	Dividends Dividends	34743000	USD
CY2018Q4	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.12
CY2018Q4	us-gaap	Dividends Dividends	6654000	USD
CY2019Q1	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.12
CY2019Q1	us-gaap	Dividends Dividends	6616000	USD
CY2019Q2	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.15
CY2019Q2	us-gaap	Dividends Dividends	8219000	USD
CY2019Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.15
CY2019Q3	us-gaap	Dividends Dividends	8185000	USD
CY2019	us-gaap	Dividends Dividends	29674000	USD
CY2020	ttek	Fair Value Adjustments To Contingent Consideration FairValueAdjustmentsToContingentConsideration	15000000.0	USD
CY2019	ttek	Fair Value Adjustments To Contingent Consideration FairValueAdjustmentsToContingentConsideration	-1100000	USD
CY2018	ttek	Fair Value Adjustments To Contingent Consideration FairValueAdjustmentsToContingentConsideration	-4300000	USD
CY2020Q3	us-gaap	Business Combination Contingent Consideration Arrangements Range Of Outcomes Value High BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh	70900000	USD
CY2020Q3	us-gaap	Business Combination Contingent Consideration Liability BusinessCombinationContingentConsiderationLiability	32600000	USD
CY2018Q3	us-gaap	Goodwill Goodwill	798820000	USD
CY2019	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	146699000	USD
CY2019	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	7755000	USD
CY2019	us-gaap	Goodwill Translation And Purchase Accounting Adjustments GoodwillTranslationAndPurchaseAccountingAdjustments	-12944000	USD
CY2019Q3	us-gaap	Goodwill Goodwill	924820000	USD
CY2020	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	80176000	USD
CY2020	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	15800000	USD
CY2020	us-gaap	Goodwill Translation And Purchase Accounting Adjustments GoodwillTranslationAndPurchaseAccountingAdjustments	4302000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	2600000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	600000	USD
CY2020Q3	us-gaap	Goodwill Goodwill	993498000	USD
CY2020Q2	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2020Q3	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	106421000	USD
CY2020Q3	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	92478000	USD
CY2019Q3	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	96722000	USD
CY2019Q3	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	80282000	USD
CY2020	us-gaap	Finite Lived Intangible Assets Foreign Currency Translation Gain Loss FiniteLivedIntangibleAssetsForeignCurrencyTranslationGainLoss	-400000	USD
CY2019	us-gaap	Finite Lived Intangible Assets Foreign Currency Translation Gain Loss FiniteLivedIntangibleAssetsForeignCurrencyTranslationGainLoss	-300000	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	11600000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	11600000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	18200000	USD
CY2020Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	8786000	USD
CY2020Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	2652000	USD
CY2020Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	1915000	USD
CY2020Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	590000	USD
CY2020Q3	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	13943000	USD
CY2020Q3	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	125511000	USD
CY2019Q3	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	149904000	USD
CY2020Q3	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	90004000	USD
CY2019Q3	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	110463000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	227991000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	175136000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	174562000	USD
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	24102000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	30051000	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	46840000	USD
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	6872000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	8923000	USD
CY2018	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	9228000	USD
CY2020	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	20398000	USD
CY2019	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	15016000	USD
CY2018	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	10897000	USD
CY2020	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	51372000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	53990000	USD
CY2018	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	66965000	USD
CY2020	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	2187000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-9108000	USD
CY2018	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-22072000	USD
CY2020	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	870000	USD
CY2019	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-1195000	USD
CY2018	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-1471000	USD
CY2020	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-328000	USD
CY2019	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-27312000	USD
CY2018	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-5817000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	2729000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-37615000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-29360000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	54101000	USD
CY2020	us-gaap	Tax Adjustments Settlements And Unusual Provisions TaxAdjustmentsSettlementsAndUnusualProvisions	0	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	16375000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	37605000	USD
CY2019	us-gaap	Tax Adjustments Settlements And Unusual Provisions TaxAdjustmentsSettlementsAndUnusualProvisions	-200000	USD
CY2018	us-gaap	Tax Adjustments Settlements And Unusual Provisions TaxAdjustmentsSettlementsAndUnusualProvisions	-300000	USD
CY2020	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.245
CY2020	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.027
CY2019	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.034
CY2018	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.042
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits Research EffectiveIncomeTaxRateReconciliationTaxCreditsResearch	0.022
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits Research EffectiveIncomeTaxRateReconciliationTaxCreditsResearch	0.047
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits Research EffectiveIncomeTaxRateReconciliationTaxCreditsResearch	0.014
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Deductions Qualified Production Activities EffectiveIncomeTaxRateReconciliationDeductionsQualifiedProductionActivities	0
CY2020Q3	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	4400000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Deductions Qualified Production Activities EffectiveIncomeTaxRateReconciliationDeductionsQualifiedProductionActivities	0
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Deductions Qualified Production Activities EffectiveIncomeTaxRateReconciliationDeductionsQualifiedProductionActivities	0.002
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	0.007
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	0.010
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	0.005
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	0.011
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	0.017
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	0.020
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Disposition Of Business EffectiveIncomeTaxRateReconciliationDispositionOfBusiness	0.015
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Disposition Of Business EffectiveIncomeTaxRateReconciliationDispositionOfBusiness	0.009
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Disposition Of Business EffectiveIncomeTaxRateReconciliationDispositionOfBusiness	0.017
CY2020	ttek	Effective Income Tax Rate Reconciliation Sharebased Payment Arrangement Percent EffectiveIncomeTaxRateReconciliationSharebasedPaymentArrangementPercent	-0.022
CY2019	ttek	Effective Income Tax Rate Reconciliation Sharebased Payment Arrangement Percent EffectiveIncomeTaxRateReconciliationSharebasedPaymentArrangementPercent	-0.024
CY2018	ttek	Effective Income Tax Rate Reconciliation Sharebased Payment Arrangement Percent EffectiveIncomeTaxRateReconciliationSharebasedPaymentArrangementPercent	-0.027
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Change In Deferred Tax Assets Valuation Allowance EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance	0.016
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Change In Deferred Tax Assets Valuation Allowance EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance	-0.135
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Change In Deferred Tax Assets Valuation Allowance EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance	-0.005
CY2020	ttek	Effective Income Tax Rate Reconciliation Change In Uncertain Tax Positions Percent EffectiveIncomeTaxRateReconciliationChangeInUncertainTaxPositionsPercent	0.004
CY2019	ttek	Effective Income Tax Rate Reconciliation Change In Uncertain Tax Positions Percent EffectiveIncomeTaxRateReconciliationChangeInUncertainTaxPositionsPercent	0.024
CY2019Q3	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	3600000	USD
CY2018	ttek	Effective Income Tax Rate Reconciliation Change In Uncertain Tax Positions Percent EffectiveIncomeTaxRateReconciliationChangeInUncertainTaxPositionsPercent	0.019
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Tax Cuts And Jobs Act Of2017 Percent EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent	0
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Tax Cuts And Jobs Act Of2017 Percent EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent	-0.014
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Tax Cuts And Jobs Act Of2017 Percent EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent	-0.084
CY2020	ttek	Effective Income Tax Rate Reconciliation Other Non Recurring Adjustments To Deferred Taxes Percent EffectiveIncomeTaxRateReconciliationOtherNonRecurringAdjustmentsToDeferredTaxesPercent	-0.013
CY2019	ttek	Effective Income Tax Rate Reconciliation Other Non Recurring Adjustments To Deferred Taxes Percent EffectiveIncomeTaxRateReconciliationOtherNonRecurringAdjustmentsToDeferredTaxesPercent	-0.004
CY2018	ttek	Effective Income Tax Rate Reconciliation Other Non Recurring Adjustments To Deferred Taxes Percent EffectiveIncomeTaxRateReconciliationOtherNonRecurringAdjustmentsToDeferredTaxesPercent	0.021
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Tax Cuts And Jobs Act Of2017 Transition Tax On Accumulated Foreign Earnings Percent EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017TransitionTaxOnAccumulatedForeignEarningsPercent	0
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Tax Cuts And Jobs Act Of2017 Transition Tax On Accumulated Foreign Earnings Percent EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017TransitionTaxOnAccumulatedForeignEarningsPercent	0.014
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Tax Cuts And Jobs Act Of2017 Transition Tax On Accumulated Foreign Earnings Percent EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017TransitionTaxOnAccumulatedForeignEarningsPercent	0
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.026
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.033
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.018
CY2020	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.237
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.093
CY2018Q3	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	1200000	USD
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.215
CY2020	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.237
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.093
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.215
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Share Based Compensation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount	-8300000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Share Based Compensation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount	-6400000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Share Based Compensation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount	-5100000	USD
CY2019	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Deferred Tax Liability Income Tax Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateDeferredTaxLiabilityIncomeTaxBenefit	2600000	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Deferred Tax Liability Income Tax Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateDeferredTaxLiabilityIncomeTaxBenefit	10100000	USD
CY2020	ttek	Effective Income Tax Rate Reconciliation Excluding Impact Of Non Deductible Goodwill Impairment And Transaction Costs Tax Benefits On Share Based Payments Tcja And Valuation Allowance Percent EffectiveIncomeTaxRateReconciliationExcludingImpactOfNonDeductibleGoodwillImpairmentAndTransactionCostsTaxBenefitsOnShareBasedPaymentsTCJAAndValuationAllowancePercent	0.256
CY2019	ttek	Effective Income Tax Rate Reconciliation Excluding Impact Of Non Deductible Goodwill Impairment And Transaction Costs Tax Benefits On Share Based Payments Tcja And Valuation Allowance Percent EffectiveIncomeTaxRateReconciliationExcludingImpactOfNonDeductibleGoodwillImpairmentAndTransactionCostsTaxBenefitsOnShareBasedPaymentsTCJAAndValuationAllowancePercent	0.246
CY2018	ttek	Effective Income Tax Rate Reconciliation Excluding Impact Of Non Deductible Goodwill Impairment And Transaction Costs Tax Benefits On Share Based Payments Tcja And Valuation Allowance Percent EffectiveIncomeTaxRateReconciliationExcludingImpactOfNonDeductibleGoodwillImpairmentAndTransactionCostsTaxBenefitsOnShareBasedPaymentsTCJAAndValuationAllowancePercent	0.303
CY2020Q3	us-gaap	Deferred Tax Assets Operating Loss Carryforwards State And Local DeferredTaxAssetsOperatingLossCarryforwardsStateAndLocal	1146000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Operating Loss Carryforwards State And Local DeferredTaxAssetsOperatingLossCarryforwardsStateAndLocal	764000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Reserves DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsReserves	6262000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Reserves DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsReserves	5500000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	6283000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Renewal Term LesseeOperatingLeaseRenewalTerm	P5Y
CY2020Q3	us-gaap	Debt Longterm And Shortterm Combined Amount DebtLongtermAndShorttermCombinedAmount	291659000	USD
CY2019Q3	us-gaap	Debt Longterm And Shortterm Combined Amount DebtLongtermAndShorttermCombinedAmount	276434000	USD
CY2020Q3	us-gaap	Debt Current DebtCurrent	49264000	USD
CY2019Q3	us-gaap	Debt Current DebtCurrent	12500000	USD
CY2020Q3	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	242395000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	7506000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities	28223000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities	28232000	USD
CY2020Q3	ttek	Deferred Tax Assets Leasing Arrangements DeferredTaxAssetsLeasingArrangements	66941000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	5905000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	6700000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Operating Loss Carryforwards Domestic DeferredTaxAssetsOperatingLossCarryforwardsDomestic	43475000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Operating Loss Carryforwards Domestic DeferredTaxAssetsOperatingLossCarryforwardsDomestic	39782000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	24395000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	20543000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	133840000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	67941000	USD
CY2020Q3	us-gaap	Deferred Tax Liabilities Tax Deferred Income DeferredTaxLiabilitiesTaxDeferredIncome	14451000	USD
CY2019Q3	us-gaap	Deferred Tax Liabilities Tax Deferred Income DeferredTaxLiabilitiesTaxDeferredIncome	21886000	USD
CY2020Q3	us-gaap	Deferred Tax Liabilities Prepaid Expenses DeferredTaxLiabilitiesPrepaidExpenses	5967000	USD
CY2019Q3	us-gaap	Deferred Tax Liabilities Prepaid Expenses DeferredTaxLiabilitiesPrepaidExpenses	3026000	USD
CY2019Q3	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	263934000	USD
CY2020Q3	us-gaap	Bank Overdrafts BankOverdrafts	33600000	USD
CY2020	ttek	Bank Overdraft Protection BankOverdraftProtection	50000000.0	USD
CY2020Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	49264000	USD
CY2020Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	15625000	USD
CY2020Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	226770000	USD
CY2020Q3	us-gaap	Debt Longterm And Shortterm Combined Amount DebtLongtermAndShorttermCombinedAmount	291659000	USD
CY2020Q3	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	66941000	USD
CY2020Q3	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	29130000	USD
CY2019Q3	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	26482000	USD
CY2020Q3	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	1615000	USD
CY2019Q3	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	1133000	USD
CY2020Q3	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	118104000	USD
CY2019Q3	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	52527000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	15736000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	15414000	USD
CY2020Q3	us-gaap	Undistributed Earnings Of Foreign Subsidiaries UndistributedEarningsOfForeignSubsidiaries	66900000	USD
CY2020	ttek	Foreign Earnings Repatriated Tax Expense Benefit ForeignEarningsRepatriatedTaxExpenseBenefit	2000000.0	USD
CY2020Q3	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	24400000	USD
CY2020Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	9200000	USD
CY2019Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	9169000	USD
CY2018Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	8328000	USD
CY2017Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	9337000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	700000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	1342000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	1928000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	0	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	356000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	1116000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	641000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	100000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	0	USD
CY2020	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	0	USD
CY2019	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	757000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	4053000	USD
CY2020Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	9228000	USD
CY2019Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	9169000	USD
CY2018Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	8328000	USD
CY2020Q3	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	35507000	USD
CY2019Q3	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	39441000	USD
CY2020	us-gaap	Depreciation Depreciation	13000000.0	USD
CY2019	us-gaap	Depreciation Depreciation	17300000	USD
CY2018	us-gaap	Depreciation Depreciation	19600000	USD
CY2019Q3	us-gaap	Assets Held For Sale Not Part Of Disposal Group AssetsHeldForSaleNotPartOfDisposalGroup	5400000	USD
CY2020	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	8500000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	209443000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	185535000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	180034000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	18548000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	-10399000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	-5472000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	136883000	USD
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	54235000	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	54986000	shares
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	87348000	USD
CY2020	us-gaap	Sublease Income SubleaseIncome	2216000	USD
CY2020	ttek	Lease Cost Other LeaseCostOther	72000	USD
CY2020	us-gaap	Lease Cost LeaseCost	85204000	USD
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	80289000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	317587000	USD
CY2020Q3	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	239396000	USD
CY2020Q3	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	69650000	USD
CY2020Q3	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	191955000	USD
CY2020Q3	us-gaap	Operating Lease Liability OperatingLeaseLiability	261605000	USD
CY2020Q3	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P5Y
CY2020Q3	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.025
CY2020Q3	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	75074000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	64972000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	44733000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	30991000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	21466000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	44169000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	281405000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	19800000	USD
CY2020Q3	us-gaap	Operating Lease Liability OperatingLeaseLiability	261605000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due OperatingLeasesFutureMinimumPaymentsDue	343500000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due Current OperatingLeasesFutureMinimumPaymentsDueCurrent	108800000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due In Two Years OperatingLeasesFutureMinimumPaymentsDueInTwoYears	66400000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due In Three Years OperatingLeasesFutureMinimumPaymentsDueInThreeYears	51400000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due In Four Years OperatingLeasesFutureMinimumPaymentsDueInFourYears	36500000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due In Five Years OperatingLeasesFutureMinimumPaymentsDueInFiveYears	25800000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due Thereafter OperatingLeasesFutureMinimumPaymentsDueThereafter	54600000	USD
CY2019	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	79300000	USD
CY2020	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	19424000	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	17618000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	19582000	USD
CY2020	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	4318000	USD
CY2019	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	4016000	USD
CY2018	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	5288000	USD
CY2020	us-gaap	Allocated Share Based Compensation Expense Net Of Tax AllocatedShareBasedCompensationExpenseNetOfTax	15106000	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense Net Of Tax AllocatedShareBasedCompensationExpenseNetOfTax	13602000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense Net Of Tax AllocatedShareBasedCompensationExpenseNetOfTax	14294000	USD
CY2019Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	894000	shares
CY2019Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	33.28
CY2020	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	355000	shares
CY2020	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	28.63
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod	0	shares
CY2020	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice	0
CY2020Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	539000	shares
CY2020Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	36.34
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P5Y14D
CY2020Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	29623000	USD
CY2020Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber	539000	shares
CY2020Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice	36.34
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Outstanding Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1	P5Y14D
CY2020	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	25000000.0	USD
CY2019	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	23300000	USD
CY2018	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	22400000	USD
CY2020Q3	us-gaap	Deferred Compensation Plan Assets DeferredCompensationPlanAssets	35100000	USD
CY2019Q3	us-gaap	Deferred Compensation Plan Assets DeferredCompensationPlanAssets	30400000	USD
CY2020Q3	us-gaap	Deferred Compensation Liability Classified Noncurrent DeferredCompensationLiabilityClassifiedNoncurrent	35000000.0	USD
CY2019Q3	us-gaap	Deferred Compensation Liability Classified Noncurrent DeferredCompensationLiabilityClassifiedNoncurrent	29500000	USD
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	173859000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	158668000	USD
CY2020Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Aggregate Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue	29623000	USD
CY2020Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber	437000	shares
CY2020Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice	34.17
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1	P4Y7M13D
CY2020Q3	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1	24932000	USD
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0	shares
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0	shares
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	55670000	shares
CY2020	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	787000	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	950000	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	928000	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	55022000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	55936000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	56598000	shares
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.21
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.89
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.46
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.16
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.84
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.42
CY2020	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2019	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2018	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	100000	shares
CY2019Q3	ttek	Loss Contingency Number Of Actions LossContingencyNumberOfActions	3	action
CY2020	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	2	segment
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2994891000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3107348000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2964148000	USD
CY2020	us-gaap	Operating Income Loss OperatingIncomeLoss	241091000	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	188762000	USD
CY2018	us-gaap	Operating Income Loss OperatingIncomeLoss	190086000	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	11600000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	11600000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	18200000	USD
CY2020	ttek	Fair Value Adjustments To Contingent Consideration FairValueAdjustmentsToContingentConsideration	15000000.0	USD
CY2019	ttek	Fair Value Adjustments To Contingent Consideration FairValueAdjustmentsToContingentConsideration	-1100000	USD
CY2018	ttek	Fair Value Adjustments To Contingent Consideration FairValueAdjustmentsToContingentConsideration	-4300000	USD
CY2020	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	15800000	USD
CY2019	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	7800000	USD
CY2020Q3	us-gaap	Assets Assets	2378558000	USD
CY2019Q3	us-gaap	Assets Assets	2147408000	USD
CY2020	us-gaap	Related Party Transaction Other Revenues From Transactions With Related Party RelatedPartyTransactionOtherRevenuesFromTransactionsWithRelatedParty	88200000	USD
CY2019	us-gaap	Related Party Transaction Other Revenues From Transactions With Related Party RelatedPartyTransactionOtherRevenuesFromTransactionsWithRelatedParty	99100000	USD
CY2018	us-gaap	Related Party Transaction Other Revenues From Transactions With Related Party RelatedPartyTransactionOtherRevenuesFromTransactionsWithRelatedParty	75000000.0	USD
CY2020	us-gaap	Related Party Transaction Expenses From Transactions With Related Party RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty	86400000	USD
CY2019	us-gaap	Related Party Transaction Expenses From Transactions With Related Party RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty	98500000	USD
CY2018	us-gaap	Related Party Transaction Expenses From Transactions With Related Party RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty	76600000	USD
CY2020Q3	us-gaap	Accounts Receivable Related Parties AccountsReceivableRelatedParties	20884000	USD
CY2019Q3	us-gaap	Accounts Receivable Related Parties AccountsReceivableRelatedParties	19351000	USD
CY2020Q3	ttek	Contract With Customer Asset Related Party ContractWithCustomerAssetRelatedParty	3261000	USD
CY2019Q3	ttek	Contract With Customer Asset Related Party ContractWithCustomerAssetRelatedParty	9681000	USD
CY2020Q3	us-gaap	Due To Related Parties Current And Noncurrent DueToRelatedPartiesCurrentAndNoncurrent	478000	USD
CY2019Q3	us-gaap	Due To Related Parties Current And Noncurrent DueToRelatedPartiesCurrentAndNoncurrent	111000	USD
CY2020Q1	ttek	Covid19 Incremental Costs COVID19IncrementalCosts	8200000	USD
CY2020Q3	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	15800000	USD
CY2019Q4	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	800000	USD
CY2020Q1	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	2200000	USD
CY2020Q2	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	4500000	USD
CY2020Q3	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	1000000.0	USD
CY2019Q3	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	7800000	USD
CY2019Q3	us-gaap	Restructuring Charges RestructuringCharges	10900000	USD
CY2019Q4	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	797623000	USD
CY2020Q1	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	734133000	USD
CY2020Q2	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	709771000	USD
CY2020Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	753364000	USD
CY2019Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	63302000	USD
CY2020Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	47530000	USD
CY2020Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	63525000	USD
CY2020Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	66735000	USD
CY2019Q4	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	47310000	USD
CY2020Q1	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	36397000	USD
CY2020Q2	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	45497000	USD
CY2020Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	44654000	USD
CY2019Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.87
CY2020Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.67
CY2020Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.84
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.83
CY2019Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.85
CY2020Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.66
CY2020Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.83
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.82
CY2019Q4	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	54560000	shares
CY2020Q1	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	54699000	shares
CY2020Q2	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	53985000	shares
CY2020Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	53841000	shares
CY2019Q4	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	55438000	shares
CY2020Q1	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	55463000	shares
CY2020Q2	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	54692000	shares
CY2020Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	54603000	shares
CY2018Q4	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	717431000	USD
CY2019Q1	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	722621000	USD
CY2019Q2	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	825793000	USD
CY2019Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	841502000	USD
CY2018Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	55711000	USD
CY2019Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	47545000	USD
CY2019Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	64841000	USD
CY2019Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	20665000	USD
CY2018Q4	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	41997000	USD
CY2019Q1	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	55911000	USD
CY2019Q2	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	49233000	USD
CY2019Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	11527000	USD
CY2018Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.76
CY2019Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.01
CY2019Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.90
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.21
CY2018Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.75
CY2019Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.00
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.88
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.21
CY2018Q4	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	55390000	shares
CY2019Q1	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	55143000	shares
CY2019Q2	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	54819000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	54617000	shares
CY2018Q4	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	56366000	shares
CY2019Q1	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	55985000	shares
CY2019Q2	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	55768000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	55618000	shares

Files In Submission

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0000831641-20-000154-index-headers.html	Edgar Link	pending
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$TTEK
TETRA TECH INC Stock $ttek

2020 Q3 Form 10-K Financial Statement

#000083164120000154 Filed on November 23, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$TTEK TETRA TECH INC Stock $ttek

2020 Q3 Form 10-K Financial Statement

#000083164120000154 Filed on November 23, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$TTEK
TETRA TECH INC Stock $ttek