Contractual Guarantees, Litigation, Investigations, and Insurance	12 Months Ended
	Sep. 30, 2022
Contractual Guarantees, Litigation, Investigations, and Insurance [Abstract]
Contractual Guarantees Litigation Investigations And Insurance	Contractual Guarantees, Litigation, Investigations and Insurance In the normal course of business, we make contractual commitments (some of which are supported by separate guarantees) and on occasion we are a party in a litigation or arbitration proceeding. The litigation or arbitration in which we are involved primarily includes personal injury claims, professional liability claims and breach of contract claims. Where we provide a separate guarantee, it is strictly in support of the underlying contractual commitment. Guarantees take various forms including surety bonds required by law, or standby letters of credit ("LOC" and also referred to as “bank guarantees”) or corporate guarantees given to induce a party to enter into a contract with a subsidiary. Standby LOCs are also used as security for advance payments or in various other transactions. The guarantees have various expiration dates ranging from an arbitrary date to completion of our work (e.g., engineering only) to completion of the overall project. See Note 18- Commitments and Contingencies and Derivative Financial Instruments for more information surrounding LOCs and surety bonds. We maintain insurance coverage for most insurable aspects of our business and operations. Our insurance programs have varying coverage limits depending upon the type of insurance, and include certain conditions and exclusions which insurance companies may raise in response to any claim that is asserted by or against the Company. We have also elected to retain a portion of certain losses, claims and liabilities that occur through the use of various deductibles, limits, and retentions under our insurance programs and utilize a number of internal financing mechanisms for these self insurance arrangements including the operation of certain captive insurance entities. As a result, we may be subject to a future liability for which we are only partially insured or completely uninsured. We intend to mitigate any such future liability by continuing to exercise prudent business judgment in negotiating the terms and conditions of the contracts which the Company enters with its clients. Our insurers are also subject to business risk and, as a result, one or more of them may be unable to fulfill their insurance obligations due to insolvency or otherwise. Additionally, as a contractor providing services to the U.S. federal government we are subject to many types of audits, investigations and claims by, or on behalf of, the government including with respect to contract performance, pricing, cost allocations, procurement practices, labor practices and socioeconomic obligations. Furthermore, our income, franchise and similar tax returns and filings are also subject to audit and investigation by the Internal Revenue Service, most states within the United States, as well as by various government agencies representing jurisdictions outside the United States. Our Consolidated Balance Sheets include amounts representing our probable estimated liability relating to such claims, guarantees, litigation, audits and investigations. We perform an analysis to determine the level of reserves to establish for insurance-related claims that are known and have been asserted against us, as well as for insurance-related claims that are believed to have been incurred based on actuarial analysis, but have not yet been reported to our claims administrators as of the respective balance sheet dates. We include any adjustments to such insurance reserves in our consolidated results of operations. Insurance recoveries are recorded as assets if recovery is probable and estimated liabilities are not reduced by expected insurance recoveries. The Company believes, after consultation with counsel, that such guarantees, litigation, U.S. government contract-related audits, investigations and claims and income tax audits and investigations should not have a material adverse effect on our consolidated financial statements, beyond amounts currently accrued. In 2012, CH2M HILL Australia PTY Limited, a subsidiary of CH2M, entered into a 50/50 integrated joint venture with Australian construction contractor UGL Infrastructure Pty Limited. The joint venture entered into a Consortium Agreement with General Electric and GE Electrical International Inc. The Consortium was awarded a subcontract by JKC Australia LNG Pty Limited ("JKC") for the engineering, procurement, construction and commissioning of a 360 MW Combined Cycle Power Plant for INPEX Operations Australia Pty Limited at Blaydin Point, Darwin, NT, Australia (the "Legacy CH2M Matter"). The subcontract was terminated in January 2017. In or around August 2017, the Consortium commenced an arbitration. On April 12, 2022, JKC and the Consortium entered into a confidential deed of settlement (“Settlement Agreement”). Under the terms of the Settlement Agreement, CH2M, as guarantor of CH2M Australia PTY Limited’s obligations with respect to the subcontract with JKC, made a cash payment to JKC in April 2022 of AUD640 million (or approximately $475 million using mid-April 2022 exchange rates). As a result of the settlement agreement, additional pre-tax charges of $91.3 million were recorded during the year ended September 30, 2022 for this matter (over amounts previously reserved and reported in long-term Other Deferred Liabilities in the Company's Consolidated Balance Sheet). The Settlement Agreement provided for a release of claims between JKC and each member of the Consortium, and in connection with this agreement the members of the Consortium also waived all claims against each other and their respective parent guarantors relating to the project. On December 22, 2008, a coal fly ash pond at the Kingston Power Plant of the Tennessee Valley Authority ("TVA") was breached, releasing fly ash waste into the Emory River and surrounding community. In February 2009, TVA awarded a contract to the Company to provide project management services associated with the clean-up. All remediation and dredging were completed in August 2013 by other contractors under direct contracts with TVA. The Company did not perform the remediation, and its scope was limited to program management services. Certain employees of the contractors performing the cleanup work on the project filed lawsuits against the Company beginning in August 2013, alleging they were injured due to the Company's failure to protect the plaintiffs from exposure to fly ash, and asserting related personal injuries. The primary case, Greg Adkisson, et al. v. Jacobs Engineering Group Inc., case No. 3:13-CV-505-TAV-HBG, filed in the U.S. District Court for the Eastern District of Tennessee, consists of 10 consolidated cases. This case and the related cases involve several hundred plaintiffs that were employees of the contractors that completed the remediation and dredging work. The cases are at various stages of litigation, and several of the cases are currently stayed pending resolution of other cases and/or appeal. Additionally, in May 2019, Roane County and the cities of Kingston and Harriman filed a lawsuit against TVA and the Company alleging that they misled the public about risks associated with the released fly ash. In October 2020, the Court granted Jacobs and TVA’s motion to dismiss the Roane County litigation and closed the case. In addition, in November 2019, a resident of Roane County, Margie Delozier, filed a putative class action against TVA and the Company alleging they failed to adequately warn local residents about risks associated with the released fly ash. The Company and TVA filed separate motions to dismiss the Delozier case in April 2020. In February 2021, the Court granted dismissal of the Delozier Complaint with prejudice, with the exception of plaintiffs’ nuisance cause of action, which plaintiffs voluntarily dismissed in June 2021. In August 2021, Thomas Ryan, a resident of Roane County, filed an action against Jacobs and TVA claiming personal injury and property damage. In June 2022, the Court granted Jacobs' motion to dismiss Ryan’s action in its entirety, closing the case. Separately, in February 2020, the Company learned that the district attorney in Roane County recommended that the Tennessee Bureau of Investigation investigate issues pertaining to clean up worker safety at Kingston. On November 16, 2021, the Roane County district attorney announced that it had concluded its investigation into issues pertaining to the Kingston coal ash spill cleanup. No indictments were issued. There has been no finding of liability against the Company or that any of the alleged illnesses are the result of exposure to fly ash in any of the above matters. The Company disputes the allegations asserted in all of the above matters and is vigorously defending these matters. The Company does not expect the resolution of these matters to have a material adverse effect on the Company's business, financial condition, results of operations or cash flows. On October 31, 2019, the Company received a request from the Enforcement Division of the Securities and Exchange Commission ("the SEC") for the production of certain information and documents. The information and documents sought by the SEC primarily relate to the operations of a joint venture in Morocco which was at one time partially-owned by the Company (and subsequently divested), including in respect of possible corrupt practices. In July 2022, the Company received a confirmatory letter from the SEC staff stating that its investigation of this matter had been terminated and that the staff does not intend to recommend an enforcement action against the Company. During fourth quarter of fiscal 2022, the Company recorded a receivable for certain expected third-party recoveries equal to approximately $27 million before tax. The Company expects the payment to be received by the second quarter of fiscal year 2023.