Earnings Per Share and Certain Related Information - Schedule of Compute Basic and Diluted of EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 29, 2023	Sep. 30, 2022	Oct. 01, 2021
Numerator for Basic and Diluted EPS:
Net earnings attributable to Jacobs from continuing operations	$ 666,619	$ 644,071	$ 467,022
Preferred Redeemable Noncontrolling interests redemption value adjustment (See Note 14- PA Consulting Business Combination)	8,340	0	(57,307)
Net earnings from continuing operations allocated to common stock for EPS calculation	674,959	644,071	409,715
Net (loss) earnings from discontinued operations allocated to common stock for EPS calculation	(842)	(32)	10,008
Net earnings allocated to common stock for EPS calculation	$ 674,117	$ 644,039	$ 419,723
Denominator for Basic and Diluted EPS:
Shares used for calculating basic EPS attributable to common stock (in shares)	126,607	128,665	130,194
Effect of dilutive securities:
Stock compensation plans (in shares)	607	780	1,080
Shares used for calculating diluted EPS attributable to common stock (in shares)	127,214	129,445	131,274
Net Earnings Per Share:
Basic Net Earnings from Continuing Operations Per Share (in dollars per share)	$ 5.33	$ 5.01	$ 3.15
Basic Net (Loss) Earnings from Discontinued Operations Per Share (in dollars per share)	(0.01)	0	0.08
Basic Earnings Per Share (in dollars per share)	5.32	5.01	3.22
Basic Earnings Per Share:
Diluted Net Earnings from Continuing Operations Per Share (in dollars per share)	5.31	4.98	3.12
Diluted Net (Loss) Earnings from Discontinued Operations Per Share (in dollars per share)	(0.01)	0	0.08
Diluted Earnings Per Share (in dollars per share)	$ 5.30	$ 4.98	$ 3.20