Basis of Presentation	3 Months Ended
Basis of Presentation	Jan. 01, 2021
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 October 2, 2020 (“2020 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 January 1, 2021, and for the three months ended January 1, 2021. 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-13 Leases for required disclosures related to leases. On November 24, 2020, a subsidiary of Jacobs completed the acquisition of Buffalo Group LLC ("Buffalo Group"), a leader in advanced cyber and intelligence solutions. The Company paid total consideration of $212.8 million, which was comprised of approximately $181.4 million in cash to the former owners of Buffalo Group and the assumption of Buffalo Group's debt of approximately $7.7 million and $23.7 million in other assumed liabilities. The Company repaid all of the assumed Buffalo Group debt by the end of the first fiscal quarter of 2021. The Company has recorded its preliminary purchase price allocation associated with the acquisition, which is summarized in Note 15- Business Combinations. On March 6, 2020, a subsidiary of Jacobs completed the acquisition of the nuclear consulting, remediation and program management business of John Wood Group, a U.K.-based energy services company, for an enterprise value of £246 million, or approximately $317.9 million, less cash acquired of $24.3 million. The Company has recorded its preliminary purchase price allocation associated with the acquisition, which is summarized in Note 15- 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 were 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. As of October 2, 2020, all of the ECR business to be sold under the terms of the ECR sale had been conveyed to Worley and as such, no amounts remain held for sale. For further discussion, see Note 16- Sale of Energy, Chemicals and Resources ("ECR") Business to the consolidated financial statements.