Stock Repurchase And Dividends [Abstract]

No definition available.

Name:	ttek_StockRepurchaseAndDividendsAbstract
Namespace Prefix:	ttek_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate dividends paid during the period for each share of common stock outstanding.

+ References

+ Details

Name:	us-gaap_CommonStockDividendsPerShareCashPaid
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

+ Details

Name:	us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of paid and unpaid cash, stock, and paid-in-kind (PIK) dividends declared, for example, but not limited to, common and preferred stock.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 405
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6957935&loc=d3e64057-112817

+ Details

Name:	us-gaap_Dividends
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

Name:	us-gaap_SubsequentEventLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Details

Name:	srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Stock Repurchase and Dividends - Schedule of Dividends Declared and Paid and Subsequent Event (Details) - USD ($) $ / shares in Units, $ in Thousands															3 Months Ended		9 Months Ended
	Sep. 04, 2020	Jul. 27, 2020	May 29, 2020	Apr. 27, 2020	Feb. 28, 2020	Jan. 27, 2020	Dec. 13, 2019	Nov. 11, 2019	May 31, 2019	Apr. 29, 2019	Feb. 28, 2019	Jan. 28, 2019	Dec. 14, 2018	Nov. 05, 2018	Jun. 28, 2020	Jun. 30, 2019	Jun. 28, 2020	Jun. 30, 2019
Stock Repurchase And Dividends [Abstract]
Dividend paid per share (in dollars per share)				$ 0.17		$ 0.15		$ 0.15		$ 0.15		$ 0.12		$ 0.12	$ 0.17	$ 0.15	$ 0.47	$ 0.39
Dividend Paid			$ 9,175		$ 8,225		$ 8,190		$ 8,219		$ 6,616		$ 6,654				$ 25,590	$ 21,489
Subsequent Event [Line Items]
Dividend paid per share (in dollars per share)				$ 0.17		$ 0.15		$ 0.15		$ 0.15		$ 0.12		$ 0.12	$ 0.17	$ 0.15	$ 0.47	$ 0.39
Subsequent Event
Subsequent Event [Line Items]
Quarterly cash dividend declared (in dollars per share)		$ 0.17
Forecast \| Subsequent Event
Stock Repurchase And Dividends [Abstract]
Dividend paid per share (in dollars per share)	$ 0.17
Subsequent Event [Line Items]
Dividend paid per share (in dollars per share)	$ 0.17