Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies MasTec is subject to a variety of legal cases, claims and other disputes that arise from time to time in the ordinary course of its business, including project contract price and acquisition purchase price disputes. MasTec cannot provide assurance that it will be successful in recovering all or any of the potential damages it has claimed or in defending claims against the Company. The outcome of such cases, claims and disputes cannot be predicted with certainty and an unfavorable resolution of one or more of them could have a material adverse effect on the Company’s business, financial condition, results of operations and cash flows. In the third quarter of 2021, a settlement was finalized in favor of MasTec for approximately $25 million, of which $19 million is due in 2022, and is recorded within other current and other long-term assets within the Company’s consolidated balance sheets, as appropriate. Net of legal and other costs incurred, the Company recorded $5 million of other income related to this settlement in the Company’s financial statements in the third quarter of 2021. Other Commitments and Contingencies Leases. In the ordinary course of business, the Company enters into non-cancelable operating leases for certain of its facility, vehicle and equipment needs, including related party leases. See Note 8 - Lease Obligations and Note 15 - Related Party Transactions. Letters of Credit. In the ordinary course of business, the Company is required to post letters of credit for its insurance carriers and surety bond providers and in support of performance under certain contracts as well as certain obligations associated with the Company’s equity investments and other strategic arrangements, including its variable interest entities. Such letters of credit are generally issued by a bank or similar financial institution. The letter of credit commits the issuer to pay specified amounts to the holder of the letter of credit under certain conditions. If this were to occur, the Company would be required to reimburse the issuer of the letter of credit, which, depending upon the circumstances, could result in a charge to earnings. As of September 30, 2021 and December 31, 2020, there were $134.9 million and $151.8 million, respectively, of letters of credit issued under the Company’s credit facilities. The Company is not aware of any material claims relating to its outstanding letters of credit as of September 30, 2021 or December 31, 2020. Performance and Payment Bonds. In the ordinary course of business, MasTec is required by certain customers to provide performance and payment bonds for contractual commitments related to its projects. These bonds provide a guarantee to the customer that the Company will perform under the terms of a contract and that the Company will pay its subcontractors and vendors. If the Company fails to perform under a contract or to pay its subcontractors and vendors, the customer may demand that the surety make payments or provide services under the bond. The Company must reimburse the surety for expenses or outlays it incurs. As of September 30, 2021 and December 31, 2020, outstanding performance and payment bonds approximated $1,723.9 million and $764.8 million, respectively, and estimated costs to complete projects secured by these bonds totaled $569.6 million and $263.2 million as of September 30, 2021 and December 31, 2020, respectively. Included in these balances as of September 30, 2021 are $115.0 million of outstanding performance and payment bonds issued on behalf of the Company’s proportionately consolidated non-controlled contractual joint ventures, representing the Company’s proportionate share of the total bond obligation for the related projects. Investment and Strategic Arrangements. The Company holds undivided interests, ranging from 85% to 90%, in multiple proportionately consolidated non-controlled contractual joint ventures that provide infrastructure construction services for electrical transmission projects, as well as undivided interests ranging from 30% to 50% in three civil construction projects. Income and/or losses incurred by these joint ventures are generally shared proportionally by the respective joint venture members, with the members of the joint ventures jointly and severally liable for all of the obligations of the joint venture. The respective joint venture agreements provide that each joint venture partner indemnify the other party for any liabilities incurred by such joint venture in excess of its ratable portion of such liabilities. Thus, it is possible that the Company could be required to pay or perform obligations in excess of its share if the other joint venture partners fail or refuse to pay or perform their respective share of the obligations. As of September 30, 2021, the Company was not aware of material future claims against it in connection with these arrangements. Included in the Company’s cash balances as of September 30, 2021 and December 31, 2020 are amounts held by entities that are proportionately consolidated totaling $10.8 million and $8.2 million, respectively. These amounts are available to support the operations of those entities, but are not available for the Company’s other operations. In addition, the Company provided $0.7 million of project-related financing to its contractual joint ventures for the nine month period ended September 30, 2021. The Company has other investment and strategic arrangements, under which it may incur costs or provide financing, performance, financial and/or other guarantees. See Note 4 - Fair Value of Financial Instruments and Note 15 - Related Party Transactions for additional information pertaining to the Company’s investment and strategic arrangements. Self-Insurance. MasTec maintains insurance policies for workers’ compensation, general liability and automobile liability, which are subject to per claim deductibles. The Company is self-insured up to the amount of the deductible. The Company also maintains excess umbrella coverage. As of September 30, 2021 and December 31, 2020, MasTec’s estimated liability for unpaid claims and associated expenses, including incurred but not reported losses related to these policies, totaled $153.6 million and $129.6 million, respectively, of which $98.7 million and $86.1 million, respectively, were reflected within other long-term liabilities in the consolidated balance sheets. MasTec also maintains an insurance policy with respect to employee group medical claims, which is subject to annual per employee maximum losses. MasTec’s estimated liability for employee group medical claims totaled $4.7 million and $4.3 million as of September 30, 2021 and December 31, 2020, respectively. The Company is required to post collateral, generally in the form of letters of credit, surety bonds and cash to certain of its insurance carriers. Insurance-related letters of credit for the Company’s workers’ compensation, general liability and automobile liability policies amounted to $64.1 million and $59.3 million as of September 30, 2021 and December 31, 2020, respectively. Outstanding surety bonds related to self-insurance programs amounted to $39.0 million and $37.4 million as of September 30, 2021 and December 31, 2020, respectively. Collective Bargaining Agreements and Multiemployer Plans. As discussed in Note 10 - Other Retirement Plans, certain of MasTec’s subsidiaries are party to various collective bargaining agreements with unions representing certain of their employees, which require the Company to pay specified wages, provide certain benefits and contribute certain amounts to MEPPs. The Employee Retirement Income Security Act of 1974, as amended by the Multiemployer Pension Plan Amendments Act of 1980 (collectively, “ERISA”), which governs U.S.-registered MEPPs, subjects employers to substantial liabilities in the event of an employer’s complete or partial withdrawal from, or upon termination of, such plans. The Company currently contributes, and in the past, has contributed to, plans that are underfunded, and, therefore, could have potential liability associated with a voluntary or involuntary withdrawal from, or termination of, these plans. As of September 30, 2021, the Company does not have plans to withdraw from, and is not aware of circumstances that would reasonably lead to material claims against it, in connection with the MEPPs in which it participates. There can be no assurance, however, that the Company will not be assessed liabilities in the future, including in the form of a surcharge on future benefit contributions or increased contributions on underfunded plans. The amount the Company could be obligated to pay or contribute in the future cannot be estimated, as these amounts are based on future levels of work of the union employees covered by these plans, investment returns, which could be negatively affected by economic and market conditions, and the level of underfunding of such plans. Indemnities. The Company generally indemnifies its customers for the services it provides under its contracts, as well as other specified liabilities, which may subject the Company to indemnity claims, liabilities and related litigation. As of September 30, 2021 and December 31, 2020, the Company was not aware of any material asserted or unasserted claims in connection with these indemnity obligations. Other Guarantees. From time to time in the ordinary course of its business, MasTec guarantees the obligations of its subsidiaries, including obligations under certain contracts with customers, certain lease obligations, and in some states, obligations in connection with obtaining contractors’ licenses. MasTec has also issued performance and other guarantees in connection with certain of its equity investments. MasTec also generally warrants the work it performs following substantial completion of a project. Much of the work performed by the Company is evaluated for defects shortly after the work is completed. If warranty claims occur, the Company could be required to repair or replace warrantied items, or, if customers elect to repair or replace the warrantied item using the services of another provider, the Company could be required to pay for the cost of the repair or replacement. Warranty claims have historically not been material. Concentrations of Risk. In the third quarter of 2021, DIRECTV® was spun off from AT&T. As a result, for customer reporting purposes, AT&T and DIRECTV® are reported separately and all prior periods have been updated to give retroactive effect to the spin off of DIRECTV® from AT&T. For the nine month period ended September 30, 2021, the Company had approximately 545 customers. As of September 30, 2021, one customer accounted for approximately 11% of the Company’s consolidated net accounts receivable position, which represents accounts receivable, net, less deferred revenue. As of December 31, 2020, two customers each accounted for approximately 15% and 12%, respectively, of the Company’s consolidated net accounts receivable position. In addition, the Company derived 58% and 60% of its revenue from its top ten customers for the three month periods ended September 30, 2021 and 2020, respectively, and derived 56% and 58% of its revenue from its top ten customers for the nine month periods ended September 30, 2021 and 2020, respectively