Discontinued Operations- Schedule of Earnings (Loss) From Discontinued Operations, Net of tax (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 27, 2025	Jun. 28, 2024	Jun. 27, 2025	Jun. 28, 2024
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Net (Loss) Earnings of the Group from Discontinued Operations	$ (1,629)	$ 67,703	$ (8,180)	$ 187,232
Net Earnings Attributable to Noncontrolling Interests from Discontinued Operations	0	(3,693)	0	(10,080)
Net (Loss) Earnings Attributable to Jacobs from Discontinued Operations	(1,629)	64,010	(8,180)	177,152
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | SpinCo Business
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues	(3,197)	1,348,196	(3,200)	4,119,108
Direct cost of contracts	3
Direct cost of contracts		(1,152,358)	0	(3,544,808)
Gross (loss) profit	(3,194)	195,838	(3,200)	574,300
Selling, general and administrative expense	(518)	(106,360)	(7,549)	(325,013)
Operating (Loss) Profit	(3,712)	89,478	(10,749)	249,287
Other income, net	0	207	0	521
(Loss) Earnings Before Taxes from Discontinued Operations	(3,712)	89,685	(10,749)	249,808
Income Tax Benefit (Expense)	1,627	(22,467)	2,102	(61,718)
Net (Loss) Earnings of the Group from Discontinued Operations	(2,085)	67,218	(8,647)	188,090
Net Earnings Attributable to Noncontrolling Interests from Discontinued Operations	0	(3,693)	0	(10,080)
Net (Loss) Earnings Attributable to Jacobs from Discontinued Operations	$ (2,085)	$ 63,525	$ (8,647)	$ 178,010