Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Employee Benefit Trust, Cash

No definition available.

Name:	jec_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedEmployeeBenefitTrustCash
Namespace Prefix:	jec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Dilutive Securities, Effect on Basic Earnings Per Share, Preference Share

+ References

No definition available.

+ Details

Name:	jec_DilutiveSecuritiesEffectOnBasicEarningsPerSharePreferenceShare
Namespace Prefix:	jec_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479830/718-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

Name:	us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479907/805-20-50-5

+ Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479328/805-10-50-2

+ Details

Name:	us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow during the period for redemption of redeemable noncontrolling interests.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 15
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-15

+ Details

Name:	us-gaap_PaymentsForRepurchaseOfRedeemableNoncontrollingInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of decrease to net income for accretion of temporary equity to its redemption value to derive net income apportioned to common stockholders.

+ References

No definition available.

+ Details

Name:	us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	srt_OwnershipAxis=jec_PAConsultingEmployeesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=jec_PAConsultingGroupLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

PA Consulting Redeemable Noncontrolling Interests - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 28, 2024	Jun. 30, 2023	Jun. 28, 2024	Jun. 30, 2023	Sep. 29, 2023	Mar. 02, 2021
Business Acquisition [Line Items]
Repurchase of redeemable noncontrolling interests			$ 41,788	$ 90,425
Preferred redeemable noncontrolling interests redemption value adjustment	$ (20)	$ 0	$ 1,746	0
Preference share effect on basic earnings per share (in dollars per share)			$ 0.01
PA Consulting Employees
Business Acquisition [Line Items]
Ownership interest of employees	70.00%		70.00%		69.00%
PA Consulting Group Limited
Business Acquisition [Line Items]
Percentage of outstanding shares of common and preferred stock acquired						65.00%
Allocated share-based compensation expense			$ 11,500	$ 5,100
Cash in employee benefit trust	$ 3,600		$ 3,600		$ 2,800