Basis of Presentation	3 Months Ended
Basis of Presentation	Dec. 27, 2019
Basis Of Presentation [Abstract]
Basis of Presentation	Basis of Presentation Unless the context otherwise requires: •References herein to “Jacobs” are to Jacobs Engineering Group Inc. and its predecessors; •References herein to the “Company”, “we”, “us” or “our” are to Jacobs Engineering Group Inc. and its consolidated subsidiaries; and •References herein to the “Group” are to the combined economic interests and activities of the Company and the persons and entities holding noncontrolling interests in our consolidated subsidiaries. The accompanying consolidated financial statements and financial information included herein have been prepared pursuant to the interim period reporting requirements of Form 10-Q. Consequently, certain information and note disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) have been condensed or omitted. Readers of this Quarterly Report on Form 10-Q should also read our consolidated financial statements and the notes thereto included in our Annual Report on Form 10-K for the fiscal year ended September 27, 2019 (“2019 Form 10-K”). In the opinion of management, the accompanying unaudited consolidated financial statements contain all adjustments (consisting of normal recurring adjustments) necessary for a fair presentation of our consolidated financial statements at December 27, 2019, and for the three months ended December 27, 2019. Our interim results of operations are not necessarily indicative of the results to be expected for the full fiscal year. Effective the beginning of fiscal first quarter 2020, the Company adopted ASU 2016-02, Leases ("ASC 842"), including the subsequent ASU's that amended and clarified the related guidance. The Company adopted ASC 842 using a modified retrospective approach, and accordingly the new guidance was applied to leases that existed or were entered into after the first day of adoption without adjusting the comparative periods presented. Please refer to Note-14 Leases for a discussion of our updated policies and disclosures related to leases. Effective the beginning of fiscal first quarter 2019, the Company adopted ASC 606, Revenue from Contracts with Customers, including the subsequent ASUs that amended and clarified the related guidance. The Company adopted ASC Topic 606 using the modified retrospective method, and accordingly the new guidance was applied retrospectively to contracts that were not completed or substantially completed as of September 29, 2018 (the date of initial application). Please refer to Note 13- Revenue Accounting for Contracts and Adoption of ASC Topic 606 for a discussion of our updated policies related to revenue recognition. On June 12, 2019, Jacobs completed the acquisition of The KeyW Holding Corporation (“KeyW”), a U.S.-based national security solutions provider to the intelligence, cyber, and counterterrorism communities by acquiring 100% of the outstanding shares of KeyW common stock. The Company paid total consideration of $902.6 million which was comprised of approximately $604.2 million in cash to the former stockholders and certain equity award holders of KeyW and the assumption of KeyW’s debt of approximately $298.4 million. The Company repaid all of the assumed KeyW debt by the end of Q4 fiscal 2019. The Company has recorded its preliminary purchase price allocation associated with the acquisition, which is summarized in Note 5- Business Combinations. On April 26, 2019, Jacobs completed the sale of its Energy, Chemicals and Resources ("ECR") business to Worley Limited, a company incorporated in Australia ("Worley"), for a purchase price of $3.4 billion consisting of (i) $2.8 billion in cash plus (ii) 58.2 million ordinary shares of Worley, subject to adjustments for changes in working capital and certain other items (the “ECR sale”). As a result of the ECR sale, substantially all ECR-related assets and liabilities have been sold (the "Disposal Group"). We determined that the Disposal Group should be reported as discontinued operations in accordance with ASC 210-05, Discontinued Operations because their disposal represents a strategic shift that had a major effect on our operations and financial results. As such, the financial results of the ECR business are reflected in our unaudited Consolidated Statements of Earnings as discontinued operations for all periods presented. Additionally, current and non-current assets and liabilities of the Disposal Group are reflected as held-for-sale in the unaudited Consolidated Balance Sheet as of September 27, 2019. Further, as of the quarter ended December 27, 2019, a portion of the ECR business remains held by Jacobs and continues to be classified as held for sale during the first quarter of fiscal 2020 in accordance with U.S. GAAP. For further discussion see Note 7- Sale of Energy, Chemicals and Resources ("ECR") Business to the consolidated financial statements.