Basis of Presentation and Accounting Policies (Policies)	9 Months Ended
	Apr. 29, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation Dycom Industries, Inc. (“Dycom” or the “Company”) is a leading provider of specialty contracting services throughout the United States and in Canada. The Company provides program management, engineering, construction, maintenance and installation services for telecommunications providers, underground facility locating services for various utilities, including telecommunications providers, and other construction and maintenance services for electric and gas utilities. The accompanying unaudited condensed consolidated financial statements include the results of Dycom and its subsidiaries, all of which are wholly-owned. All intercompany accounts and transactions have been eliminated. In the opinion of management, all adjustments (consisting of normal and recurring adjustments) considered necessary for a fair statement of the results for the interim periods presented have been included. These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X of the Securities and Exchange Commission (“SEC”). Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. Operating results for the interim period are not necessarily indicative of the results expected for any other interim period or for the full fiscal year. These condensed consolidated financial statements and accompanying notes should be read in conjunction with Management’s Discussion and Analysis of Financial Condition and Results of Operations contained in this report and the Company’s audited financial statements for the year ended July 30, 2016 included in the Company’s Annual Report on Form 10-K for the year ended July 30, 2016, filed with the SEC on August 31, 2016.
Segment Information	Segment Information. The Company operates in one reportable segment. Its services are provided by its operating segments on a decentralized basis. Each operating segment consists of a subsidiary (or in certain instances, the combination of two or more subsidiaries). Management of the operating segments report to the Company’s Chief Operating Officer who reports to the Chief Executive Officer, the chief operating decision maker. All of the Company’s operating segments have been aggregated into one reportable segment based on their similar economic characteristics, nature of services and production processes, type of customers, and service distribution methods. The Company’s operating segments provide services throughout the United States and in Canada. Revenues from services provided in Canada were not material during the three or nine months ended April 29, 2017 and April 23, 2016. Additionally, the Company had no material long-lived assets in Canada as of April 29, 2017 or July 30, 2016.
Accounting Period	Accounting Period. The Company’s fiscal year ends on the last Saturday in July. As a result, each fiscal year consists of either 52 weeks or 53 weeks of operations (with the additional week of operations occurring in the fourth quarter). Fiscal 2016 consisted of 53 weeks of operations and fiscal 2017 will consist of 52 weeks of operations.
Use of Estimates	Use of Estimates. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the amounts reported in these condensed consolidated financial statements and accompanying notes. These estimates are based on the Company’s historical experience and management’s understanding of current facts and circumstances. At the time they are made, the Company believes that such estimates are fair when considered in conjunction with the consolidated financial position and results of operations taken as a whole. However, actual results could differ materially from those estimates. There have been no material changes to the Company’s significant accounting policies and critical accounting estimates described in the Company’s Annual Report on Form 10-K for the year ended July 30, 2016.
Revenue Recognition, Policy	Revenue Recognition. The Company performs a majority of its services under master service agreements and other agreements that contain customer-specified service requirements, such as discrete pricing for individual tasks. Revenue is recognized under these arrangements based on units-of-delivery as each unit is completed. The remainder of the Company’s services, representing less than 5% of its contract revenues during each of the nine months ended April 29, 2017 and April 23, 2016, are performed under contracts using the cost-to-cost measure of the percentage of completion method of accounting. Revenue is recognized under these arrangements based on the ratio of contract costs incurred to date to total estimated contract costs. For contracts using the cost-to-cost measure of the percentage of completion method of accounting, the Company accrues the entire amount of a contract loss at the time the loss is determined to be probable and can be reasonably estimated. During the nine months ended April 29, 2017 and April 23, 2016, there were no material impacts to the Company’s results of operations due to changes in contract estimates. There were no material amounts of unapproved change orders or claims recognized during the nine months ended April 29, 2017 or April 23, 2016. The current asset “Costs and estimated earnings in excess of billings” represents revenues recognized in excess of amounts billed. The current liability “Billings in excess of costs and estimated earnings” represents billings in excess of revenues recognized.
Goodwill and Intangible Assets	Goodwill and Intangible Assets. The Company accounts for goodwill and other intangibles in accordance with ASC Topic 350, Intangibles - Goodwill and Other (“ASC Topic 350”). Goodwill and other indefinite-lived intangible assets are assessed annually for impairment as of the first day of the fourth fiscal quarter of each year, or more frequently if events occur that would indicate a potential reduction in the fair value of a reporting unit below its carrying value. The Company performs its annual impairment review of goodwill at the reporting unit level. Each of the Company’s operating segments with goodwill represents a reporting unit for the purpose of assessing impairment. If the Company determines the fair value of the reporting unit’s goodwill or other indefinite-lived intangible assets is less than their carrying value as a result of the tests, an impairment loss is recognized and reflected in operating income or loss in the consolidated statements of operations during the period incurred. In accordance with ASC Topic 360, Impairment or Disposal of Long-Lived Assets, the Company reviews finite-lived intangible assets for impairment whenever an event occurs or circumstances change that indicates that the carrying amount of such assets may not be fully recoverable. Recoverability is determined based on an estimate of undiscounted future cash flows resulting from the use of an asset and its eventual disposition. Should an asset not be recoverable, an impairment loss is measured by comparing the fair value of the asset to its carrying value. If the Company determines the fair value of an asset is less than the carrying value, an impairment loss is recognized in operating income or loss in the consolidated statements of operations during the period incurred. The Company uses judgment in assessing whether goodwill and intangible assets are impaired. Estimates of fair value are based on the Company’s projection of revenues, operating costs, and cash flows taking into consideration historical and anticipated future results, general economic and market conditions, as well as the impact of planned business or operational strategies. The Company determines the fair value of its reporting units using a weighting of fair values derived equally from the income approach and the market approach valuation methodologies. The income approach uses the discounted cash flow method and the market approach uses the guideline company method. Changes in the Company’s judgments and projections could result in significantly different estimates of fair value, potentially resulting in impairments of goodwill and other intangible assets. The inputs used for fair value measurements of the reporting units and other related indefinite-lived intangible assets are the lowest level (Level 3) inputs. See Note 7, Goodwill and Intangible Assets, for additional information regarding the Company’s annual assessment of goodwill and other indefinite-lived intangible assets and additional disclosure regarding recently acquired operations.
Other Assets	Other Assets. As of April 29, 2017 and July 30, 2016, other non-current assets consisted of deferred financing costs related to the Company’s revolving credit facility of $5.2 million and $6.4 million, respectively, insurance recoveries/receivables related to accrued claims of $8.9 million and $5.7 million, respectively, as well as other long-term deposits, prepaid discounts, and other non-current assets totaling $10.8 million and $12.7 million, respectively. Additionally, other non-current assets included $5.4 million and $5.0 million of restricted cash held as collateral in support of the Company’s insurance obligations as of April 29, 2017 and July 30, 2016, respectively. Changes in restricted cash are reported in cash flows used in investing activities in the condensed consolidated statements of cash flows. As of April 29, 2017 and July 30, 2016, other non-current assets also included $4.0 million for an investment in nonvoting senior units of a former customer, which is accounted for using the cost method.
Fair Value of Financial Instruments	Fair Value of Financial Instruments. The Company’s financial instruments primarily consist of cash and equivalents, restricted cash, accounts receivable, income taxes receivable and payable, accounts payable, certain accrued expenses, and long-term debt. The carrying amounts of these items approximate fair value due to their short maturity, except for certain of the Company’s outstanding long-term debt, which is based on observable market-based inputs (Level 2). See Note 10, Debt, for further information regarding the fair value of such financial instruments. The Company’s cash and equivalents are based on quoted market prices in active markets for identical assets (Level 1) as of April 29, 2017 and July 30, 2016. During the nine months ended April 29, 2017 and April 23, 2016, the Company had no material nonrecurring fair value measurements of assets or liabilities subsequent to their initial recognition.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements There have been no changes in the expected dates of adoption or estimated effects on the Company’s consolidated financial statements of recently issued accounting pronouncements from those disclosed in the Company’s Annual Report on Form 10-K for the year ended July 30, 2016 filed with the SEC on August 31, 2016. Accounting standards adopted during the period covered in this Quarterly Report on Form 10-Q and recently issued accounting pronouncements are discussed below. Recently Adopted Accounting Standards Business Combinations. In September 2015, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments (“ASU 2015-16”). ASU 2015-16 replaces the requirement for an acquirer in a business combination to retrospectively adjust provisional amounts recognized at the acquisition date with a corresponding adjustment to goodwill when measurement period adjustments are identified. The new guidance requires an acquirer to recognize adjustments in the reporting period in which the adjustment amounts are determined. The acquirer must record, in the same period’s financial statements, the effect on earnings of changes in depreciation, amortization, or other income effects, if any, as a result of the change to the provisional amounts, calculated as if the accounting had been completed at the acquisition date. Additionally, the acquirer must present separately on the face of the income statement, or disclose in the notes, the portion of the amount recorded in current period earnings by line item that would have been recorded in previous reporting periods if the adjustments had been recognized as of the acquisition date. The Company adopted ASU 2015-16 during the first quarter of fiscal 2017 and it did not have a material effect on the Company’s consolidated financial statements. Accounting Standards Not Yet Adopted Goodwill. In January 2017, the FASB issued Accounting Standards Update No. 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (“ASU 2017-04”). ASU 2017-04 simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment testing. An entity will no longer determine goodwill impairment by calculating the implied fair value of goodwill by assigning the fair value of a reporting unit to all of its assets and liabilities as if that reporting unit had been acquired in a business combination. Instead, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value. The loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. ASU 2017-04 will be effective for the Company in fiscal 2021 and interim reporting periods within that year. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company expects the adoption of this guidance will not have a material effect on the Company’s consolidated financial statements. Business Combinations. In January 2017, the FASB issued Accounting Standards Update No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business (“ASU 2017-01”). The amendments in this update clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions or disposals of assets or businesses. ASU 2017-01 will be effective for the Company in fiscal 2019 and interim reporting periods within that year. Early adoption is permitted for transactions that have not been reported in financial statements that have been issued or made available for issuance. The Company expects the adoption of this guidance will not have a material effect on the Company’s consolidated financial statements. Revenue Recognition. In December 2016, the FASB issued Accounting Standards Update No. 2016-20, Technical Corrections and Improvements to Topic 606: Revenue from Contracts with Customers (“ASU 2016-20”). The amendments in this update affect certain aspects of the guidance issued in ASU 2014-09, including impairment testing of contract costs, contract loss provisions, and performance obligation disclosure. ASU 2016-08, 2016-10, ASU 2016-12, and 2016-20 must be adopted concurrently with ASU 2014-09. ASU 2014-09 will be effective for the Company beginning in fiscal 2019 and interim reporting periods within that year, using either the retrospective or cumulative effect transition method. The Company is currently evaluating the transition methods and the effect of the adoption of this guidance on the Company’s consolidated financial statements. Restricted Cash. In November 2016, the FASB issued Accounting Standards Update No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (“ASU 2016-18”). ASU 2016-18 is intended to reduce the diversity in practice regarding the classification and presentation of changes in restricted cash within the statement of cash flows. The amendments in this update require that amounts generally described as restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU 2016-18 will be effective for the Company in fiscal 2019 and interim reporting periods within that year. Early adoption is permitted, including adoption in an interim period. If an entity early adopts the amendments in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes that interim period. The Company expects the adoption of this guidance will not have a material effect on the Company’s consolidated financial statements. Income Taxes. In October 2016, the FASB issued Accounting Standards Update No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (“ASU 2016-16”). ASU 2016-16 amends the current GAAP prohibition of recognizing current and deferred income taxes for intra-entity asset transfers until the asset has been sold to an outside party. The update requires an entity to recognize the income tax consequences of an intra-entity transfer for assets other than inventory when the transfer occurs. ASU 2016-16 will be effective for the Company in fiscal 2019 and interim reporting periods within that year. Early adoption is permitted as of the beginning of an interim or annual reporting period. The Company expects the adoption of this guidance will not have a material effect on the Company’s consolidated financial statements. Statement of Cash Flows. In August 2016, the FASB issued Accounting Standards Update No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”). ASU 2016-15 is intended to reduce the diversity in practice regarding the classification of certain transactions within the statement of cash flows. ASU 2016-15 will be effective for the Company in fiscal 2019 and interim reporting periods within that year. Early adoption is permitted as of the beginning of an interim or annual reporting period. The Company expects the adoption of this guidance will not have a material effect on the Company’s consolidated financial statements. Stock Compensation - In March 2016, the FASB issued Accounting Standards Update No. 2016-09, Compensation - Stock Compensation (Topic 718) Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”). ASU 2016-09 includes provisions intended to simplify accounting for share-based payment transactions including income tax consequences, classification of share-based awards as either equity or liabilities, and classification on the statement of cash flows. Under ASU 2016-09, all excess tax benefits (or tax deficiencies) will be recognized as income tax benefit (or expense) in the statement of operations. Additionally, when applying the treasury stock method for computing diluted earnings per share under ASU 2016-09 the assumed proceeds will not include any windfall tax benefits, which may result in a greater number of dilutive shares outstanding. Further, excess tax benefits will be classified along with other income tax cash flows as an operating activity. ASU 2016-09 also permits income tax withholding up to the maximum statutory tax rate in applicable jurisdictions as the threshold to qualify for equity classification. ASU 2016-09 will be effective for the Company in fiscal 2018 and interim reporting periods within that year. Early adoption is permitted as of the beginning of an interim or annual reporting period with all adjustments to be reflected as of the beginning of the fiscal year of adoption. The application of ASU 2016-09 will result in greater volatility in the effective tax rate in future periods.