Fair Value of Financial Instruments	9 Months Ended
Fair Value of Financial Instruments	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Note 5 – Fair Value of Financial Instruments The Company’s financial instruments include cash and cash equivalents, accounts and notes receivable, cash collateral deposited with insurance carriers, life insurance assets, cost and equity method investments, deferred compensation plan assets and liabilities, accounts payable and other current liabilities, acquisition-related contingent consideration, certain intangible assets and liabilities, including off-market contracts, and debt obligations. Fair value is the price that would be received to sell an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value guidance establishes a valuation hierarchy, which requires maximizing the use of observable inputs when measuring fair value. The three levels of inputs that may be used are: (i) Level 1 - quoted market prices in active markets for identical assets or liabilities; (ii) Level 2 - observable market based inputs or other observable inputs; and (iii) Level 3 - significant unobservable inputs that cannot be corroborated by observable market data, which are generally determined using valuation models incorporating management estimates of market participant assumptions. In instances in which the inputs used to measure fair value fall into different levels of the fair value hierarchy, the fair value measurement classification is determined based on the lowest level input that is significant to the fair value measurement in its entirety. Management’s assessment of the significance of a particular item to the fair value measurement in its entirety requires judgment, including the consideration of inputs specific to the asset or liability. Fair values of financial instruments are estimated using public market prices, quotes from financial institutions and other available information. Due to their short-term maturity, the carrying amounts of cash and cash equivalents, accounts receivable and accounts payable and other current liabilities approximate their fair values. Management believes the carrying values of notes receivable, cash collateral deposited with insurance carriers, deferred compensation plan assets and liabilities and outstanding balances on its credit facilities approximate their fair values. Cost and equity method investments are initially recorded at their cost basis. Assets and Liabilities Measured at Fair Value on a Recurring Basis As of September 30, 2015 and December 31, 2014, financial instruments required to be measured at fair value on a recurring basis consisted primarily of acquisition-related contingent consideration liabilities, which represent the estimated fair value of additional future earn-outs payable for acquisitions of businesses (“ASC 805 contingent consideration”), in accordance with U.S. GAAP. The fair value of ASC 805 contingent consideration is based on management estimates and entity-specific assumptions, which are Level 3 inputs, and is evaluated on an ongoing basis. As of September 30, 2015 and December 31, 2014, the fair value of the Company’s ASC 805 contingent consideration totaled $94.0 million and $146.1 million, respectively. There were no additions to ASC 805 contingent consideration from new business combinations for the three month periods ended September 30, 2015 or 2014, or for the nine month period ended September 30, 2015. Additions from new business combinations were $33.6 million for the nine month period ended September 30, 2014. The Company paid approximately $5.5 million, $37.7 million, $1.3 million and $48.3 million, respectively, in connection with ASC 805 contingent consideration for the three and nine month periods ended September 30, 2015 and 2014. For the three and nine month periods ended September 30, 2015, the Company recognized net reductions of $4.4 million and $8.0 million, respectively, of ASC 805 contingent consideration, which related primarily to finalization of earn-out arrangements in the Oil and Gas, Electrical Transmission and Communications segments, and were recorded within other expense (income), net, in the condensed unaudited consolidated statements of operations. Foreign currency translation gains associated with ASC 805 contingent consideration for the three and nine month periods ended September 30, 2015 and 2014 were $2.8 million, $6.4 million, $2.9 million and $2.5 million, respectively. Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis Assets and liabilities recognized or disclosed at fair value on a non-recurring basis, for which remeasurement occurs in the event of an impairment or other measurement event, if applicable, include items such as cost and equity method investments, life insurance assets, long-lived assets, goodwill, other intangible assets and liabilities, including off-market contracts and debt. As of both September 30, 2015 and December 31, 2014, the carrying amount of the Company’s 4.875% senior notes due 2023 (the “4.875% Senior Notes”) totaled $400 million. As of September 30, 2015 and December 31, 2014, the estimated fair value of the Company’s 4.875% Senior Notes, based on quoted market prices in active markets, a Level 1 input, totaled $332.0 million and $375.0 million, respectively. Cost and Equity Method Investments. The aggregate carrying value of the Company’s cost and equity method investment assets, including long-term receivables from investees and contractual joint ventures, totaled approximately $68.0 million and $17.7 million as of September 30, 2015 and December 31, 2014, respectively. In June 2015, MasTec invested $6 million, and committed to future equity contributions and/or loan guarantees of up to an additional $78 million, for a 33% equity interest in two joint ventures. As of September 30, 2015, the Company had invested $51 million in these joint ventures and expects to satisfy its remaining commitments in the fourth quarter of 2015. From time to time, MasTec may elect to advance additional amounts above its commitments to fund temporary capital requirements. The joint ventures were formed to design, build, own and operate a header system and two pipelines that will transport natural gas. A subsidiary of MasTec will construct the pipelines, with construction expected to commence in 2016. Each pipeline is planned to interconnect at the United States/Mexico border with pipelines currently under development and construction in Mexico. The fair values of the Company’s cost and equity method investments are not readily available. The Company is not aware of events or changes in circumstances that would have a significant adverse effect on the carrying values of its cost and/or equity method investments as of September 30, 2015 or December 31, 2014.

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.