Business, Basis of Presentation and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) for interim financial information and with the instructions for Form 10-Q and Rule 10-01 of Regulation S-X. Pursuant to these rules and regulations, certain information and footnote disclosures normally included in the annual audited consolidated financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. The accompanying condensed consolidated balance sheet as of December 31, 2014 is derived from the Company’s audited financial statements as of that date. Because certain information and footnote disclosures have been condensed or omitted, these condensed unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto as of and for the year ended December 31, 2014 contained in the 2014 Form 10-K. In management’s opinion, all normal and recurring adjustments considered necessary for a fair presentation of the financial position, results of operations and cash flows for the periods presented have been included. Certain prior year amounts have been reclassified to conform to the current period presentation. Interim period operating results do not necessarily indicate the results that may be expected for any other interim period or for the full fiscal year. The Company believes that the disclosures made in these condensed unaudited consolidated financial statements are adequate to make the information not misleading.
Reclassifications	Certain prior year amounts have been reclassified to conform to the current period presentation.
Principles of Consolidation	Principles of Consolidation The accompanying condensed unaudited consolidated financial statements include MasTec, Inc. and its subsidiaries and include the accounts of all majority owned subsidiaries over which the Company exercises control and, when applicable, entities in which the Company has a controlling financial interest. Other parties’ interests in companies for which MasTec exercises control and has a controlling financial interest are reported as non-controlling interests within equity. Net income or loss attributable to non-controlling interests is reported as a separate line item below net income or loss. The Company’s investments in entities in which the Company does not have a controlling interest, but for which it has the ability to exert significant influence, are accounted for using the equity method of accounting. Equity method investments are recorded as other long-term assets in the condensed unaudited consolidated balance sheets. Income or loss from these investments is recorded within other income or expense in the condensed unaudited consolidated statements of operations. The cost method is used for investments in entities in which the Company does not have the ability to exert significant influence. All significant intercompany balances and transactions have been eliminated in consolidation. The assets and liabilities of foreign subsidiaries with a functional currency other than the U.S. dollar are translated into U.S. dollars at period-end exchange rates, with resulting translation gains or losses accumulated within other comprehensive income or loss. Revenue and expenses are translated into U.S. dollars at average rates of exchange during the applicable period. Substantially all of the Company’s foreign operations use the local currency as the functional currency. Gains or losses resulting from transactions executed in a foreign currency are included in other income or expense, net. The Company does not currently have subsidiaries that operate in highly inflationary environments. The results of operations and financial position of any discontinued operations are aggregated and presented separately from the Company’s continuing operations in the condensed unaudited consolidated financial statements for all periods presented.
Translation of Foreign Currencies	The assets and liabilities of foreign subsidiaries with a functional currency other than the U.S. dollar are translated into U.S. dollars at period-end exchange rates, with resulting translation gains or losses accumulated within other comprehensive income or loss. Revenue and expenses are translated into U.S. dollars at average rates of exchange during the applicable period. Substantially all of the Company’s foreign operations use the local currency as the functional currency. Gains or losses resulting from transactions executed in a foreign currency are included in other income or expense, net. The Company does not currently have subsidiaries that operate in highly inflationary environments.
Investments in Affiliates and Other Entities	Investments in Affiliates and Other Entities In the ordinary course of business, the Company enters into various investment arrangements, which may include equity or other interests in business entities, including contractual joint ventures or other forms of equity participation. These investment arrangements may include financing arrangements, such as the extension of loans. See Note 3 - Acquisitions and Note 5 - Fair Value of Financial Instruments for discussion pertaining to certain of the Company’s cost and equity method investments and other investment arrangements. In connection with certain of these investment arrangements, the Company provides infrastructure construction services to or through its equity investees and/or contractual joint ventures. Management determines whether such investment arrangements involve a variable interest entity (“VIE”) based on the characteristics of the particular entity. If an entity is determined to be a VIE, then management determines if the Company is the primary beneficiary of the entity and whether or not consolidation of the VIE within the Company's financial statements is required. The primary beneficiary consolidating the VIE must normally have both (i) the power to direct the primary activities of the VIE and (ii) the obligation to absorb losses of the VIE or the right to receive benefits from the VIE, which, in either case, could be significant to the VIE. If management determines that the Company is the primary beneficiary of a VIE, then the VIE would be consolidated, and the other party’s equity interest in the VIE would be accounted for as a non-controlling interest. As of September 30, 2015, the Company determined that certain of its investment arrangements were VIEs, but that it was not the primary beneficiary. In arrangements in which the Company has an undivided interest in the assets, liabilities, revenues and profits or losses of an unincorporated entity, such amounts are consolidated on a basis proportional to the Company’s ownership interest in the unincorporated entity.
Variable Interest Entities	In the ordinary course of business, the Company enters into various investment arrangements, which may include equity or other interests in business entities, including contractual joint ventures or other forms of equity participation. These investment arrangements may include financing arrangements, such as the extension of loans. See Note 3 - Acquisitions and Note 5 - Fair Value of Financial Instruments for discussion pertaining to certain of the Company’s cost and equity method investments and other investment arrangements. In connection with certain of these investment arrangements, the Company provides infrastructure construction services to or through its equity investees and/or contractual joint ventures. Management determines whether such investment arrangements involve a variable interest entity (“VIE”) based on the characteristics of the particular entity. If an entity is determined to be a VIE, then management determines if the Company is the primary beneficiary of the entity and whether or not consolidation of the VIE within the Company's financial statements is required. The primary beneficiary consolidating the VIE must normally have both (i) the power to direct the primary activities of the VIE and (ii) the obligation to absorb losses of the VIE or the right to receive benefits from the VIE, which, in either case, could be significant to the VIE. If management determines that the Company is the primary beneficiary of a VIE, then the VIE would be consolidated, and the other party’s equity interest in the VIE would be accounted for as a non-controlling interest.
Unincorporated Joint Ventures, Proportionate Consolidation	In arrangements in which the Company has an undivided interest in the assets, liabilities, revenues and profits or losses of an unincorporated entity, such amounts are consolidated on a basis proportional to the Company’s ownership interest in the unincorporated entity.
Management Estimates	Management Estimates The preparation of financial statements in conformity with U.S. GAAP requires the use of estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Key estimates include: the recognition of revenue and project profit or loss (which the Company defines as project revenue, less project costs of revenue, including depreciation), in particular, on long-term construction contracts, or other projects accounted for under the percentage-of-completion method, for which the recorded amounts require estimates of costs to complete projects, ultimate project profit and the amount of contract price adjustments that are probable; allowances for doubtful accounts; estimated fair values of goodwill and intangible assets and liabilities, acquisition-related contingent consideration and investments in cost and equity method investees; asset lives used in computing depreciation and amortization; accrued self-insured claims; share-based compensation; accounting for income taxes; and the estimated impact of contingencies and ongoing litigation. While management believes that such estimates are fair when considered in conjunction with its consolidated financial position and results of operations taken as a whole, actual results could differ from those estimates and such differences could be material to the condensed unaudited consolidated financial statements.
Revenue Recognition	Revenue Recognition Revenue is derived from projects performed under master and other service agreements as well as from fixed price contracts for specific projects or jobs requiring the construction and installation of an entire infrastructure system or specified units within an entire infrastructure system. The Company frequently provides maintenance, installation and repair work under unit price or fixed price master service or other service agreements that are renewed on a periodic basis. Revenue and related costs for master and other service agreements billed on a time and materials basis are recognized as the services are rendered. Revenue derived from projects performed under master service and other service agreements totaled 44% and 43% of revenue for the three month periods ended September 30, 2015 and 2014, respectively, and totaled 47% and 49% of revenue, respectively, for the nine month periods ended September 30, 2015 and 2014. The Company also performs services under master and other service agreements on a fixed fee basis, under which MasTec furnishes specified units of service for a fixed price per unit of service and revenue is recognized as the services are rendered. Revenue from fixed price contracts provides for a fixed amount of revenue for the entire project, subject to certain additions for changed scope or specifications. Revenue from these contracts, as well as for certain projects pursuant to master and other service agreements, is recognized using the percentage-of-completion method, under which the percentage of revenue to be recognized for a given project is measured by the percentage of costs incurred to date on the contract to the total estimated costs for the contract. Such contracts provide that the customer accept completion of progress to date and compensate the Company for services rendered, which may be measured in terms of costs incurred, units installed, hours expended or some other measure of progress. Contract costs include all direct materials, labor and subcontracted costs and those indirect costs related to contract performance, such as indirect labor, supplies, tools, repairs and the operational costs of capital equipment (excluding depreciation). Much of the materials associated with the Company’s work are customer-furnished and are therefore not included in contract revenue and costs. The estimation process for revenue recognized under the percentage-of-completion method is based on the professional knowledge and experience of the Company’s engineers, project managers and financial professionals. Management reviews estimates of contract revenue and costs on an ongoing basis. Changes in job performance, job conditions and final contract settlements are factors that influence management’s assessment of total contract value and total estimated costs to complete those contracts and, therefore, the Company’s profit recognition. Changes in these factors may result in revisions to costs and income, and their effects are recognized in the period in which the revisions are determined, which could materially affect the Company’s results of operations in the period in which such changes are recognized. Excluding the effects of project losses of $21.4 million on a Canadian wind project and $8.3 million on a non-controlled proportionately consolidated Canadian joint venture for the nine month period ended September 30, 2015, project profit was affected by less than 5% for both the nine month periods ended September 30, 2015 and 2014 as a result of changes in contract estimates included in projects that were in process as of December 31, 2014 and 2013, respectively. Provisions for losses on uncompleted contracts are made in the period in which such losses are determined to be probable and the amount can be reasonably estimated. The majority of fixed price contracts are generally completed within one year. The Company may incur costs subject to change orders, whether approved or unapproved by the customer, and/or claims related to certain contracts. Management determines the probability that such costs will be recovered based upon engineering studies and legal opinions, past practices with the customer, specific discussions, correspondence or preliminary negotiations with the customer. The Company treats project costs as a cost of contract performance in the period incurred if it is not probable that the costs will be recovered, or defers costs and/or recognizes revenue up to the amount of the related cost if it is probable that the contract price will be adjusted and can be reliably estimated. As of September 30, 2015 and December 31, 2014, the Company had approximately $28 million and $87 million, respectively, of change orders and/or claims that had been included as contract price adjustments on certain contracts that were in the process of being resolved in the normal course of business, including through negotiation, arbitration and other proceedings. These contract price adjustments, which are included within costs and earnings in excess of billings, or billed accounts receivable as appropriate, represent management’s best estimate of contract revenue that has been or will be earned and that management believes is probable of collection. As of both September 30, 2015 and December 31, 2014, outstanding change orders and/or claims were derived from contracts in the Electrical Transmission and Oil and Gas segments. The Company actively engages in substantive meetings with these customers to complete the final approval process and expects these processes to be completed within one year. The amounts ultimately realized upon final acceptance by its customers could be higher or lower than such estimated amounts. Billings in excess of costs and estimated earnings on uncompleted contracts are classified as current liabilities. Costs and estimated earnings in excess of billings, or work in process, is classified within current assets for the majority of the Company’s projects. Work in process on contracts is based on work performed but not yet billed to customers as per individual contract terms.
Revenue Recognition, Percentage-of-Completion Method	Revenue from fixed price contracts provides for a fixed amount of revenue for the entire project, subject to certain additions for changed scope or specifications. Revenue from these contracts, as well as for certain projects pursuant to master and other service agreements, is recognized using the percentage-of-completion method, under which the percentage of revenue to be recognized for a given project is measured by the percentage of costs incurred to date on the contract to the total estimated costs for the contract. Such contracts provide that the customer accept completion of progress to date and compensate the Company for services rendered, which may be measured in terms of costs incurred, units installed, hours expended or some other measure of progress. Contract costs include all direct materials, labor and subcontracted costs and those indirect costs related to contract performance, such as indirect labor, supplies, tools, repairs and the operational costs of capital equipment (excluding depreciation). Much of the materials associated with the Company’s work are customer-furnished and are therefore not included in contract revenue and costs. The estimation process for revenue recognized under the percentage-of-completion method is based on the professional knowledge and experience of the Company’s engineers, project managers and financial professionals. Management reviews estimates of contract revenue and costs on an ongoing basis. Changes in job performance, job conditions and final contract settlements are factors that influence management’s assessment of total contract value and total estimated costs to complete those contracts and, therefore, the Company’s profit recognition. Changes in these factors may result in revisions to costs and income, and their effects are recognized in the period in which the revisions are determined, which could materially affect the Company’s results of operations in the period in which such changes are recognized. Excluding the effects of project losses of $21.4 million on a Canadian wind project and $8.3 million on a non-controlled proportionately consolidated Canadian joint venture for the nine month period ended September 30, 2015, project profit was affected by less than 5% for both the nine month periods ended September 30, 2015 and 2014 as a result of changes in contract estimates included in projects that were in process as of December 31, 2014 and 2013, respectively. Provisions for losses on uncompleted contracts are made in the period in which such losses are determined to be probable and the amount can be reasonably estimated. The majority of fixed price contracts are generally completed within one year.
New Accounting Pronouncements	New Accounting Pronouncements Accounting Standards Not Yet Adopted In September 2015, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments (“ASU 2015-16”). ASU 2015-16 eliminates the requirement to retrospectively account for adjustments to provisional amounts within the measurement period recognized at the acquisition date in a business combination. ASU 2015-16 requires that these adjustments be recognized in the reporting period in which the adjustment amounts are determined and be calculated as if the accounting had been completed as of the acquisition date. ASU 2015-16 is effective prospectively for fiscal years, and for interim periods within those years, beginning after December 15, 2015. Early application is permitted. The Company is currently evaluating the impact of this ASU on its consolidated financial statements. In July 2015, the FASB issued ASU 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory (“ASU 2015-11”). ASU 2015-11 requires that inventory measured using any method other than last-in, first out (“LIFO”) or the retail inventory method to be subsequently measured at the lower of cost or net realizable value, rather than at the lower of cost or market value. Under this ASU, subsequent measurement of inventory using the LIFO and retail inventory method is unchanged. ASU 2015-11 is effective prospectively for fiscal years, and for interim periods within those years, beginning after December 15, 2016. Early application is permitted. The Company is currently evaluating the impact of this ASU on its consolidated financial statements. In April 2015, the FASB issued ASU 2015-05, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement. ASU 2015-05 provides guidance for determining whether a cloud computing arrangement includes a software license and requires that all software licenses within the scope of Subtopic 350-40 be accounted for in a manner consistent with other licenses of intangible assets. ASU 2015-05 is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2015. Early application is permitted. Retrospective application is permitted for all relevant prior periods. The Company is currently evaluating the potential impact of this ASU on its consolidated financial statements. In April 2015, the FASB issued ASU 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs (“ASU 2015-03”). ASU 2015-03 requires that debt issuance costs related to a recognized debt liability be presented as a direct deduction from the carrying amount of the debt, consistent with debt discounts. ASU 2015-03 is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2015. Early application is permitted. Retrospective application is required for all relevant prior periods. In August 2015, the FASB issued ASU 2015-15, Interest - Imputation of Interest (Subtopic 835-30): Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements - Amendments to SEC Paragraphs Pursuant to Staff Announcement at June 18, 2015 EITF Meeting (SEC Update) (“ASU 2015-15”). ASU 2015-15 clarifies that, subsequent to adoption of ASU 2015-03, an entity has the option to defer and present debt issuance costs from line-of-credit arrangements as an asset and subsequently amortize the costs ratably over the term of the line-of-credit arrangement, regardless of whether there are any outstanding borrowings on the line-of-credit arrangement. The Company does not expect the adoption of ASU 2015-03 or ASU 2015-15 to have a material impact on its consolidated financial statements. In February 2015, the FASB issued ASU 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis (“ASU 2015-02”). ASU 2015-02 changes the evaluation that a reporting entity must perform to determine whether it should consolidate certain types of legal entities, reduces the number of consolidation models and places emphasis on risk of loss when determining a controlling financial interest. Under ASU 2015-02, all entities are within the scope of Accounting Standards Codification (“ASC”) Subtopic 810, Consolidation, including limited partnerships and similar legal entities, unless a scope exception applies. The presumption that a general partner controls a limited partnership has been eliminated. In addition, fees paid to decision makers that meet certain conditions no longer cause consolidation of VIEs in certain instances. The amendments place more emphasis on variable interests other than fee arrangements and reduce the extent to which related party arrangements cause an entity to be considered a primary beneficiary. ASU 2015-02 is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2015. Early application is permitted. The Company is currently evaluating the potential impact of this ASU on its consolidated financial statements. In January 2015, the FASB issued ASU 2015-01, Income Statement - Extraordinary and Unusual Items (Subtopic 225-20): Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary Items (“ASU 2015-01”). ASU 2015-01 eliminates the presentation and disclosure requirements of extraordinary items because it was unclear when an item should be considered both unusual and infrequent and was extremely rare in practice. ASU 2015-01 is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2015. The Company does not expect the adoption of this ASU to have an impact on its consolidated financial statements. In November 2014, the FASB issued ASU 2014-16, Derivatives and Hedging (Topic 815): Determining Whether the Host Contract in a Hybrid Financial Instrument Issued in the Form of a Share is More Akin to Debt or to Equity (a consensus of the FASB Emerging Issues Task Force) (“ASU 2014-16”). The amendments in ASU 2014-16 do not change the current criteria in U.S. GAAP for determining when separation of certain embedded derivative features in a hybrid financial instrument is required. Rather, ASU 2014-16 clarifies how current U.S. GAAP should be interpreted in evaluating the economic characteristics and risks of a host contract in a hybrid financial instrument that is issued in the form of a share. ASU 2014-16 is effective for existing hybrid financial instruments issued in the form of a share on a modified retrospective basis for fiscal years, and for interim periods within those years, beginning after December 15, 2015. Retrospective application is permitted for all relevant prior periods. The Company does not expect the adoption of this ASU to have an impact on its consolidated financial statements. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”). The core principle of this ASU is that a company will recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration to which it expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under current guidance and will be required to disclose information about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including disclosure of assumptions and estimates where significant judgment has been applied. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which delayed the effective date of ASU 2014-09 by one year. ASU 2014-09, as amended, is effective using either the retrospective or cumulative effect transition method for fiscal years, and for interim periods within those years, beginning after December 15, 2017. Early application is permitted, but not before fiscal years, and interim periods within those years, beginning after December 15, 2016. The Company is currently determining which transition method will be used and evaluating the potential impact of this ASU on its consolidated financial statements. Recently Adopted Accounting Pronouncements In April 2014, the FASB issued ASU 2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity (“ASU 2014-08”). ASU 2014-08 changes the requirements for reporting discontinued operations and requires additional disclosures about discontinued operations. Only disposals of components of an entity representing a strategic shift that has, or will have, a major effect on an entity’s operations and financial results should be reported as discontinued operations under ASU 2014-08. Examples include a disposal of a major geographical area, a major line of business, or a major equity method investment. ASU 2014-08 also requires expanded disclosure about discontinued operations and requires disclosure about individually significant dispositions that do not qualify as a discontinued operation. ASU 2014-08 is effective prospectively for fiscal years, and for interim periods within those years, beginning after December 15, 2014. The Company adopted ASU 2014-08 as of January 1, 2015. The adoption of this ASU did not have an impact on the Company’s condensed unaudited consolidated financial statements, but could impact whether future disposals of operations would qualify as discontinued operations.