Commitments and Contingencies	9 Months Ended
Jun. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies In the normal course of business, we are subject to certain contractual guarantees and litigation. The guarantees to which we are a party generally relate to project schedules and plant performance. Most of the litigation in which we are involved has us as a defendant in workers’ compensation, personal injury, environmental, employment/labor, professional liability, and other similar lawsuits. We maintain insurance coverage for various aspects of our business and operations. Our insurance programs have varying coverage limits and maximums, and insurance companies may seek to not pay any claims we might make. We have also elected to retain a portion of losses that occur through the use of various deductibles, limits, and retentions under our insurance programs. As a result, we may be subject to 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 our contracts. 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 and several of its agencies, we are subject to many levels of audits, investigations, and claims by, or on behalf of, the U.S. federal government with respect to our contract performance, pricing, costs, cost allocations, and procurement practices. 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 U.S., as well as by various government agencies representing jurisdictions outside the U.S. We record in our Consolidated Balance Sheets amounts representing our estimated liability relating to such claims, guarantees, litigation, and 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, and 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. 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 any material adverse effect on our consolidated financial statements. On September 30, 2015, Nui Phao Mining Company Limited (“NPMC”) commenced arbitration proceedings against Jacobs E&C Australia Pty Limited (“Jacobs E&C”). The arbitration is pending in Singapore before the Singapore International Arbitration Centre. In March 2011, Jacobs E&C was engaged by NPMC for the provision of management, design, engineering, and procurement services for the Nui Phao mine/mineral processing project in Vietnam. In the Notice of Arbitration and in a subsequently filed Statement of Claim and Supplementary Statement of Claim dated February 1, 2016 and February 26, 2016, respectively, NPMC asserts various causes of action and alleges that the quantum of its claim exceeds $167 million. Jacobs has denied liability and is vigorously defending this claim. A hearing on the merits has been set for November 2017. The Company does not expect the resolution of this matter to have a material adverse effect on its financial condition, results of operations and/or cash flows. On December 7, 2009, the Judicial Council of California, Administrative Office of the Courts (“AOC”) initiated an action in the San Francisco County Superior Court against Jacobs Facilities Inc. (“JFI”) and Jacobs Project Management (“JPM”) and subsequently added Jacobs as a defendant. The action arises out of a contract between AOC and JFI pursuant to which JFI provided regular maintenance and repairs at certain AOC court facilities. AOC has alleged, among other things, that the Jacobs entities are required under California’s Contractors’ State License Law (“CSLL”) to disgorge certain fees paid by AOC, and the Jacobs entities have, among other things, cross-claimed for unpaid sums for work performed. On May 2, 2012, the jury returned a special verdict in favor of the Jacobs entities finding, among other things, JPM was owed approximately $4.7 million in unpaid fees and that JFI was not required to disgorge the approximate $18.3 million that AOC had paid for work performed. On August 20, 2015, the California Court of Appeal reversed the jury’s verdict, holding that JFI had violated the CSLL. The Court of Appeal remanded to the San Francisco County Superior Court for an evidentiary hearing to determine whether the JFI had “substantially complied” with the CSLL under California Business and Professions Code Section 7031(e). Establishing “substantial compliance” would prevent $18.3 million in disgorgement against Jacobs and permit Jacobs to recover $4.7 million. The evidentiary hearing on substantial compliance was conducted between July 18 and August 5, 2016. On December 29, 2016, the court issued a Statement of Decision in favor of the Company, finding that Jacobs Facilities had substantially complied with the CSLL, and entered a judgment in favor of JPM in the amount of $4.7 million plus prejudgment interest. On January 30, 2017, AOC filed a notice of appeal. The Company does not expect the resolution of this matter to have a material adverse effect on its financial condition, results of operations and/or cash flows.

Commitments and Contingencies

In the normal course of business, we are subject to certain contractual guarantees and litigation. The guarantees to which we are a party generally relate to project schedules and plant performance. Most of the litigation in which we are involved has us as a defendant in workers’ compensation, personal injury, environmental, employment/labor, professional liability, and other similar lawsuits.

We maintain insurance coverage for various aspects of our business and operations. Our insurance programs have varying coverage limits and maximums, and insurance companies may seek to not pay any claims we might make. We have also elected to retain a portion of losses that occur through the use of various deductibles, limits, and retentions under our insurance programs. As a result, we may be subject to 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 our contracts. 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 and several of its agencies, we are subject to many levels of audits, investigations, and claims by, or on behalf of, the U.S. federal government with respect to our contract performance, pricing, costs, cost allocations, and procurement practices. 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 U.S., as well as by various government agencies representing jurisdictions outside the U.S.

We record in our Consolidated Balance Sheets amounts representing our estimated liability relating to such claims, guarantees, litigation, and 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, and 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.

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 any material adverse effect on our consolidated financial statements.

On September 30, 2015, Nui Phao Mining Company Limited (“NPMC”) commenced arbitration proceedings against Jacobs E&C Australia Pty Limited (“Jacobs E&C”). The arbitration is pending in Singapore before the Singapore International Arbitration Centre. In March 2011, Jacobs E&C was engaged by NPMC for the provision of management, design, engineering, and procurement services for the Nui Phao mine/mineral processing project in Vietnam. In the Notice of Arbitration and in a subsequently filed Statement of Claim and Supplementary Statement of Claim dated February 1, 2016 and February 26, 2016, respectively, NPMC asserts various causes of action and alleges that the quantum of its claim exceeds $167 million. Jacobs has denied liability and is vigorously defending this claim. A hearing on the merits has been set for November 2017. The Company does not expect the resolution of this matter to have a material adverse effect on its financial condition, results of operations and/or cash flows.

On December 7, 2009, the Judicial Council of California, Administrative Office of the Courts (“AOC”) initiated an action in the San Francisco County Superior Court against Jacobs Facilities Inc. (“JFI”) and Jacobs Project Management (“JPM”) and subsequently added Jacobs as a defendant. The action arises out of a contract between AOC and JFI pursuant to which JFI provided regular maintenance and repairs at certain AOC court facilities. AOC has alleged, among other things, that the Jacobs entities are required under California’s Contractors’ State License Law (“CSLL”) to disgorge certain fees paid by AOC, and the Jacobs entities have, among other things, cross-claimed for unpaid sums for work performed. On May 2, 2012, the jury returned a special verdict in favor of the Jacobs entities finding, among other things, JPM was owed approximately $4.7 million in unpaid fees and that JFI was not required to disgorge the approximate $18.3 million that AOC had paid for work performed.

On August 20, 2015, the California Court of Appeal reversed the jury’s verdict, holding that JFI had violated the CSLL. The Court of Appeal remanded to the San Francisco County Superior Court for an evidentiary hearing to determine whether the JFI had “substantially complied” with the CSLL under California Business and Professions Code Section 7031(e). Establishing “substantial compliance” would prevent $18.3 million in disgorgement against Jacobs and permit Jacobs to recover $4.7 million. The evidentiary hearing on substantial compliance was conducted between July 18 and August 5, 2016. On December 29, 2016, the court issued a Statement of Decision in favor of the Company, finding that Jacobs Facilities had substantially complied with the CSLL, and entered a judgment in favor of JPM in the amount of $4.7 million plus prejudgment interest. On January 30, 2017, AOC filed a notice of appeal. The Company does not expect the resolution of this matter to have a material adverse effect on its financial condition, results of operations and/or cash flows.