Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Jun. 28, 2026 |
Jun. 29, 2025 |
Jun. 28, 2026 |
Jun. 29, 2025 |
|
| Income Statement [Abstract] | ||||
| Revenue | $ 1,308,555 | $ 1,369,816 | $ 3,739,374 | $ 4,112,490 |
| Subcontractor costs | (199,996) | (216,800) | (544,007) | (658,439) |
| Other costs of revenue | (865,354) | (901,477) | (2,517,701) | (2,766,854) |
| Gross profit | 243,205 | 251,539 | 677,666 | 687,197 |
| Selling, general and administrative expenses | (85,203) | (86,611) | (254,653) | (255,022) |
| Legal contingency costs | 0 | 0 | 0 | (115,000) |
| Contingent consideration – fair value adjustments | (77) | 58 | 7,429 | 2,355 |
| Impairment of goodwill | 0 | 0 | 0 | (92,416) |
| Income from operations | 157,925 | 164,986 | 430,442 | 227,114 |
| Interest expense, net | (7,158) | (8,288) | (23,124) | (23,996) |
| Other non-operating income | 0 | 0 | 12,361 | 0 |
| Income before income tax expense | 150,767 | 156,698 | 419,679 | 203,118 |
| Income tax expense | (40,966) | (42,815) | (110,858) | (83,045) |
| Net income | 109,801 | 113,883 | 308,821 | 120,073 |
| Net income attributable to noncontrolling interests | (217) | (39) | (586) | (94) |
| Net income attributable to Tetra Tech | 109,584 | 113,844 | 308,235 | 119,979 |
| Net income attributable to Tetra Tech | $ 109,584 | $ 113,844 | $ 308,235 | $ 119,979 |
| Earnings per share attributable to Tetra Tech: | ||||
| Basic (in dollars per share) | $ 0.42 | $ 0.43 | $ 1.19 | $ 0.45 |
| Diluted (in dollars per share) | $ 0.42 | $ 0.43 | $ 1.18 | $ 0.45 |
| Weighted-average common shares outstanding: | ||||
| Basic (in shares) | 258,151 | 263,026 | 259,685 | 265,589 |
| Diluted (in shares) | 259,779 | 264,855 | 261,459 | 268,113 |
| X | ||||||||||
- Definition Fair Value Adjustments To Contingent Consideration No definition available.
|
| X | ||||||||||
- Definition The aggregate amount is comprised primarily of marketing and bid and proposal costs, and corporate headquarters' costs related to the executives offices, finance, accounting, administration and information technology, including non-contract related portion of stock-based compensation, depreciation of property and equipment and amortization of identifiable intangible assets. No definition available.
|
| X | ||||||||||
- Definition The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities. Reference 1: http://www.xbrl.org/2003/role/exampleRef
|
| X | ||||||||||
- References No definition available.
|
| X | ||||||||||
- Definition The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Amount of impairment loss from asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- References No definition available.
|
| X | ||||||||||
- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Amount of interest expense classified as nonoperating. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition The amount of expense provided in the period for legal costs incurred on or before the balance sheet date pertaining to resolved, pending or threatened litigation, including arbitration and mediation proceedings. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Amount of Net Income (Loss) attributable to noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities, and addition from assumption of issuance of common shares for dilutive potential common shares; of income (loss) available to common shareholders. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition The net result for the period of deducting operating expenses from operating revenues. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Other costs incurred during the reporting period related to other revenue generating activities. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition Amount of income (expense) related to nonoperating activities, classified as other. Reference 1: http://www.xbrl.org/2003/role/exampleRef
|
| X | ||||||||||
- Definition The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- References No definition available.
|
| X | ||||||||||
- Definition Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|