Discontinued Operations- Schedule of Earnings (Loss) From Discontinued Operations, Net of tax (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 28, 2025	Mar. 29, 2024	Mar. 28, 2025	Mar. 29, 2024
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Net (Loss) Earnings of the Group from Discontinued Operations	$ (5,550)	$ 72,889	$ (6,551)	$ 119,530
Net Earnings Attributable to Noncontrolling Interests from Discontinued Operations	0	(3,013)	0	(6,388)
Net (loss) earnings attributable to Jacobs from discontinued operations	(5,550)	69,876	(6,551)	113,142
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff \| SpinCo Business
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues	(67)	1,421,914	(3)	2,770,912
Direct cost of contracts	58
Direct cost of contracts		(1,229,261)	(3)	(2,392,450)
Gross (loss) profit	(9)	192,653	(6)	378,462
Selling, general and administrative expense	(5,683)	(94,908)	(7,031)	(218,653)
Operating (Loss) Profit	(5,692)	97,745	(7,037)	159,809
Other income, net	0	(167)	0	314
(Loss) Earnings Before Taxes from Discontinued Operations	(5,692)	97,578	(7,037)	160,123
Income Tax Benefit (Expense)	132	(23,919)	475	(39,251)
Net (Loss) Earnings of the Group from Discontinued Operations	(5,560)	73,659	(6,562)	120,872
Net Earnings Attributable to Noncontrolling Interests from Discontinued Operations	0	(3,013)	0	(6,388)
Net (loss) earnings attributable to Jacobs from discontinued operations	$ (5,560)	$ 70,646	$ (6,562)	$ 114,484

Disposal Group, Including Discontinued Operation, Costs of Goods Sold, Net of Expense Reversal

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Disposal Group, Including Discontinued Operation, Other Income, Net of Expenses

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Amount before tax of income (loss) from a discontinued operation. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

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Amount of tax expense (benefit) related to a discontinued operation. Includes, but is not limited to, tax expense (benefit) related to income (loss) from operations during the phase-out period, tax expense (benefit) related to gain (loss) on disposal, tax expense (benefit) related to gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and tax expense (benefit) related to adjustments of a prior period gain (loss) on disposal.

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Amount of general and administrative expense attributable to disposal group, including, but not limited to, discontinued operation.

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Amount of gross profit attributable to disposal group, including, but not limited to, discontinued operation.

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Amount after tax of income (loss) from a discontinued operation including the portion attributable to the noncontrolling interest. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

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