Consolidated Statements of Earnings - USD ($) $ in Thousands	12 Months Ended
	Oct. 02, 2020	Sep. 27, 2019	Sep. 28, 2018
Income Statement [Abstract]
Revenues	$ 13,566,975	$ 12,737,868	$ 10,579,773
Direct cost of contracts	(10,980,307)	(10,260,840)	(8,421,223)
Gross profit	2,586,668	2,477,028	2,158,550
Selling, general and administrative expenses	(2,050,695)	(2,072,177)	(1,771,107)
Operating Profit	535,973	404,851	387,443
Other Income (Expense):
Interest income	4,729	9,487	8,984
Interest expense	(62,206)	(83,847)	(76,760)
Miscellaneous (expense) income, net	(37,293)	20,468	11,314
Total other expense, net	(94,770)	(53,892)	(56,462)
Earnings from Continuing Operations Before Taxes	441,203	350,959	330,981
Income Tax Expense for Continuing Operations	(55,320)	(36,954)	(325,632)
Net Earnings of the Group from Continuing Operations	385,883	314,005	5,349
Net Earnings of the Group from Discontinued Operations	137,984	559,214	167,793
Net Earnings of the Group	523,867	873,219	173,142
Net Earnings Attributable to Noncontrolling Interests from Continuing Operations	(32,022)	(23,045)	(9,534)
Net Earnings (Loss) Attributable to Jacobs from Continuing Operations	353,861	290,960	(4,185)
Net Earnings Attributable to Noncontrolling Interests from Discontinued Operations	0	(2,195)	(177)
Net Earnings Attributable to Jacobs from Discontinued Operations	137,984	557,019	167,616
Net Earnings Attributable to Jacobs	$ 491,845	$ 847,979	$ 163,431
Net Earnings (Loss) Per Share:
Basic Net Earnings (Loss) from Continuing Operations Per Share (in dollars per share)	$ 2.69	$ 2.11	$ (0.03)
Basic Net Earnings from Discontinued Operations Per Share (in dollars per share)	1.05	4.03	1.21
Basic Earnings Per Share (in dollars per share)	3.74	6.14	1.18
Diluted Net Earnings (Loss) from Continuing Operations Per Share (in dollars per share)	2.67	2.09	(0.03)
Diluted Net Earnings from Discontinued Operations Per Share (in dollars per share)	1.04	4.00	1.21
Diluted Earnings Per Share (in dollars per share)	$ 3.71	$ 6.08	$ 1.18