Basis of Presentation (Policies)	9 Months Ended
Basis of Presentation (Policies)	Jun. 29, 2018
Basis Of Presentation [Abstract]
Use of Estimates and Assumptions	Use of Estimates and Assumptions The preparation of financial statements in conformity with U.S. GAAP requires us to employ estimates and make assumptions that affect the reported amounts of certain assets and liabilities, the revenues and expenses reported for the periods covered by the accompanying consolidated financial statements, and certain amounts disclosed in these Notes to the Consolidated Financial Statements. Although such estimates and assumptions are based on management’s most recent assessment of the underlying facts and circumstances utilizing the most current information available and past experience, actual results could differ significantly from those estimates and assumptions. Our estimates, judgments, and assumptions are evaluated periodically and adjusted accordingly. Please refer to Note 2 Significant Accounting Policies of Notes to Consolidated Financial Statements included in our 2017 Form 10-K for a discussion of the significant estimates and assumptions affecting our consolidated financial statements.
Fair Value and Fair Value Measurements	Fair Value and Fair Value Measurements Certain amounts included in the accompanying consolidated financial statements are presented at “fair value.” Fair value is defined as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants as of the date fair value is determined (the “measurement date”). When determining fair value, we consider the principal or most advantageous market in which we would transact, and we consider only those assumptions we believe a typical market participant would consider when pricing an asset or liability. In measuring fair value, we use the following inputs in the order of priority indicated: Level 1 - Quoted prices in active markets for identical assets or liabilities. Level 2 - Observable inputs other than quoted prices in active markets included in Level 1, such as (i) quoted prices for similar assets or liabilities; (ii) quoted prices in markets that have insufficient volume or infrequent transactions (e.g., less active markets); and (iii) model-driven valuations in which all significant inputs are observable or can be derived principally from, or corroborated with, observable market data for substantially the full term of the asset or liability. Level 3 - Unobservable inputs to the valuation methodology that are significant to the fair value measurement. Please refer to Note 2 Significant Accounting Policies of Notes to Consolidated Financial Statements included in our 2017 Form 10-K for a more complete discussion of the various items within the consolidated financial statements measured at fair value and the methods used to determine fair value. The net carrying amounts of cash and cash equivalents, trade receivables and payables, and notes payable approximate fair value due to the short-term nature of these instruments. See Note 11 Long Term Debt for a discussion of the fair value of long-term debt.
New Accounting Pronouncements	New Accounting Pronouncements From time to time, the Financial Accounting Standards Board (“FASB”) issues accounting standards updates (each being an “ASU”) to its Accounting Standards Codification (“ASC”), which constitutes the primary source of U.S. GAAP. The Company regularly monitors ASUs as they are issued and considers their applicability to its business. All ASUs applicable to the Company are adopted by their effective dates and in the manner prescribed by the FASB. Revenue Recognition In May 2014, the FASB issued ASU No. 2014-09 Revenue from Contracts with Customers. The new guidance provided by ASU 2014-09 is intended to remove inconsistencies and perceived weaknesses in the existing revenue requirements, provide a more robust framework for addressing revenue issues, improve comparability, provide more useful information and simplify the preparation of financial statements. The effective date for ASU 2014-09 is for annual reporting periods beginning after December 15, 2017 and interim periods therein. The Company’s adoption activities are being performed over three phases: (i) assessment, (ii) design, and (iii) implementation. Our assessment and design phases are complete. We have established a cross-functional team to implement ASU 2014-09. As part of the implementation process, the Company has identified the following potentially significant differences to date: Performance Obligations Under current U.S. GAAP, the Company typically segments contracts that contain multiple services by service type, such as engineering, procurement and construction services, for purposes of revenue recognition. Under ASU 2014-09, multiple-service contracts where the Company is responsible for providing a single deliverable (e.g., a constructed asset) will be treated as a single performance obligation for purposes of revenue recognition and thus no longer will be segmented. Typically, this will occur when the company is contracted to perform both engineering and construction on a project. In these circumstances, the timing and pattern of revenue recognition will change. The remainder of the Company's contracts will continue to be treated as a single unit of account because they either contain only one service or because the Company has determined that the component services in the contract are distinct. Contract Modifications In many instances, the Company enters into separate contracts for related services (e.g., engineering and construction) but is held responsible for providing a single deliverable (“Phased Projects”). Under ASU 2014-09, the separate contracts may be required to be combined and treated as a single contract with one performance obligation. This modification or combination of contracts may result in a cumulative catchup adjustment, which will have an immediate impact on the Company’s results of operations in the period the contract combination or modification occurs. In addition, it will change the timing and pattern of revenue recognition after the period the contracts have been combined or modified. The Company analyzed its current Phased Projects and concluded that a number of these arrangements would be combined under ASU 2014-09. Based on the two noted changes above, the Company has identified selected changes to our systems, processes and internal controls and designed updates for each to meet the standard's revised reporting and disclosure requirements. The Company has also assessed the impact of ASU 2014-09 to the recently acquired CH2M business. We will align CH2M's accounting policies, processes and controls with the policies, processes and controls being implemented across the Company. The Company will adopt the new standard using the Modified Retrospective application. This standard could have a significant impact on the Company’s Consolidated Financial Statements and an administrative impact on its operations. The impact will depend on the magnitude of the items discussed above. While the Company will continue to evaluate the impact through the implementation phase, we expect a downward adjustment to retained earnings in the period of adoption due to revenue timing for certain engineering and construction contracts shifting when they are accounted for as a single performance obligation. Lease Accounting In February 2016, the FASB issued ASU 2016-02 Leases. ASU 2016-02 requires lessees to recognize assets and liabilities for most leases. ASU 2016-02 is effective for public entity financial statements for annual periods beginning after December 15, 2018, and interim periods within those annual periods. Early adoption is permitted, including adoption in an interim period. The new guidance currently requires a modified retrospective transition approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. In January 2018, the FASB released an exposure draft that, if issued in its current form, would provide us with the option to adopt the provisions of the new guidance prospectively, without adjusting the comparative periods presented. The Company is evaluating the impact of the new guidance on its consolidated financial statements. This standard could have a significant administrative impact on its operations, and the Company will further assess the impact through its implementation program. Other Pronouncements In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. ASU 2017-12 provides financial reporting improvements related to hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements. Additionally, ASU No. 2017-12 makes certain targeted improvements to simplify the application of the hedge accounting guidance. The revised guidance becomes effective for fiscal years beginning after December 15, 2018 with early adoption permitted. The Company is evaluating the impact of the new guidance on its consolidated financial statements. It is not expected that the updated guidance will have a significant impact on the Company’s consolidated financial statements. ASU 2017-04, Simplifying the Test for Goodwill Impairment, is effective for fiscal years beginning after December 15, 2019 with early adoption permitted. ASU 2017-04 removes the second step of the goodwill impairment test, which requires a hypothetical purchase price allocation. An entity will now recognize a goodwill impairment charge for the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the amount of goodwill allocated to the reporting unit. Management does not expect the adoption of ASU 2017-04 to have any impact on the Company's financial position, results of operations or cash flows. In March 2017, the FASB issued ASU No. 2017-07, Compensation- Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. This new standard intends to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost. The new standard requires the service cost component of net periodic cost be reported in the same line item(s) as other employee compensation costs and all other components of the net periodic cost be reported in the consolidated statements of earnings and comprehensive income below operating income. ASU 2017-7 is effective for fiscal years beginning after December 15, 2017 for public companies and early adoption is permitted. Management is currently evaluating the impact that the adoption of ASU 2017-07 will have on the Company's financial position, results of operations and cash flows. In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, which allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. ASU 2018-02 is effective for interim and annual reporting periods beginning after December 15, 2018, with early adoption permitted. Management is currently evaluating the impact that the adoption of ASU 2018-02 will have on the Company's financial position, results of operations and cash flows.