Cover Page - shares	9 Months Ended
	Jun. 26, 2020	Jul. 23, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 26, 2020
Document Transition Report	false
Entity File Number	1-7463
Entity Registrant Name	JACOBS ENGINEERING GROUP INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	95-4081636
Entity Address, Address Line One	1999 Bryan Street
Entity Address, Address Line Two	Suite 1200
Entity Address, City or Town	Dallas
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75201
City Area Code	214
Local Phone Number	583 – 8500
Title of 12(b) Security	Common Stock
Trading Symbol	J
Security Exchange Name	NYSE
Entity Central Index Key	0000052988
Current Fiscal Year End Date	--10-02
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		130,208,041