Earnings Per Share and Certain Related Information - Schedule of EPS to Denominator (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 26, 2020	Jun. 28, 2019	Jun. 26, 2020	Jun. 28, 2019
Numerator for Basic and Diluted EPS:
Net earnings attributable to Jacobs from continuing operations	$ 226,886	$ 89,365	$ 284,344	$ 269,012
Net earnings from continuing operations allocated to participating securities	(24)	(105)	(77)	(444)
Net earnings from continuing operations allocated to common stock for EPS calculation	226,862	89,260	284,267	268,568
Net earnings attributable to Jacobs from discontinued operations	18,043	435,077	125,511	436,642
Net earnings from discontinued operations allocated to participating securities	(2)	(513)	(34)	(720)
Net earnings from discontinued operations allocated to common stock for EPS calculation	18,041	434,564	125,477	435,922
Net earnings allocated to common stock for EPS calculation	$ 244,903	$ 523,824	$ 409,744	$ 704,490
Denominator for Basic and Diluted EPS:
Weighted average basic shares (in shares)	130,229	136,772	131,995	139,263
Shares allocated to participating securities (in shares)	(14)	(161)	(36)	(230)
Shares used for calculating basic EPS attributable to common stock (in shares)	130,215	136,611	131,959	139,033
Effect of dilutive securities:
Stock compensation plans (in shares)	1,048	1,212	1,188	1,206
Shares used for calculating diluted EPS attributable to common stock (in shares)	131,263	137,823	133,147	140,239
Basic Earnings Per Share
Basic Net (Loss) Earnings from Continuing Operations Per Share (in dollars per share)	$ 1.74	$ 0.65	$ 2.15	$ 1.93
Basic Net Earnings from Discontinued Operations Per Share (in dollars per share)	0.14	3.18	0.95	3.14
Basic (Loss) Earnings Per Share (in dollars per share)	1.88	3.83	3.11	5.07
Diluted Earnings Per Share
Diluted Net (Loss) Earnings from Continuing Operations Per Share (in dollars per share)	1.73	0.65	2.13	1.92
Diluted Net Earnings from Discontinued Operations Per Share (in dollars per share)	0.14	3.15	0.94	3.11
Diluted (Loss) Earnings Per Share (in dollars per share)	$ 1.87	$ 3.80	$ 3.08	$ 5.02