Commitments and Contingencies	3 Months Ended
Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 14 – 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 April 2019, an arbitral tribunal award related to a Canadian acquisition was finalized (the “Award”) for approximately $50 million in favor of MasTec. The collectibility of the Award is uncertain and currently under review. Additionally, MasTec has incurred significant arbitration, legal and other costs related to this matter and expects to incur additional costs while pursuing collection of the Award. 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, surety bond providers and in support of performance under certain contracts as well as certain obligations associated with the Company’s equity investments, 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 March 31, 2019 and December 31, 2018, there were $130.7 million and $128.4 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 March 31, 2019 or December 31, 2018. 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 projects in process. 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 subcontractors and vendors. If the Company fails to perform under a contract or to pay 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 March 31, 2019 and December 31, 2018, outstanding performance and payment bonds approximated $233.1 million and $123.6 million, respectively, and estimated costs to complete projects secured by these bonds totaled $61.3 million and $53.0 million as of March 31, 2019 and December 31, 2018, respectively. These amounts do not include performance and payment bonds associated with the Company’s equity investments. Investment Arrangements. From time to time, the Company may participate in selected investment or strategic arrangements to expand its operations, customer base or geographic reach, including arrangements that combine the Company’s skills and resources with those of others to allow for the performance of particular projects. 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. The Company also holds a 35% undivided interest in a proportionately consolidated non-controlled Canadian contractual joint venture that was underway when the Company acquired Pacer in 2014, whose sole activity involves the construction of a bridge, a business in which the Company does not otherwise engage. This joint venture, which is managed by a third party, and for which the Company has minimal direct construction involvement, automatically terminates upon completion of the project. 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 March 31, 2019, the Company was not aware of circumstances that would reasonably lead to material future claims against it in connection with these arrangements. Included in the Company’s cash balances as of March 31, 2019 and December 31, 2018 are amounts held by entities that are proportionately consolidated totaling $26.7 million and $11.8 million, respectively. These amounts are available to support the operations of those entities, but are not available for the Company’s other operations. Advances on project work associated with the Company’s proportionately consolidated contractual joint ventures, which are reflected within other current liabilities, totaled $3.4 million and $7.0 million as of March 31, 2019 and December 31, 2018. The Company has other investment 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 details regarding the Company’s other investment 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 March 31, 2019 and December 31, 2018, MasTec’s liability for unpaid claims and associated expenses, including incurred but not reported losses related to these policies, totaled $112.8 million and $108.9 million, respectively, of which $73.1 million and $70.8 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 $3.1 million and $2.9 million as of March 31, 2019 and December 31, 2018, 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 $67.6 million as of both March 31, 2019 and December 31, 2018. Outstanding surety bonds related to self-insurance programs amounted to $34.8 million as of both March 31, 2019 and December 31, 2018. In addition, cash collateral deposited with insurance carriers, which is included within other long-term assets, amounted to $1.6 million for these policies as of both March 31, 2019 and December 31, 2018. Employment Agreements. The Company has employment agreements with certain executives and other employees, which provide for compensation and certain other benefits and for severance payments under certain circumstances. Certain employment agreements also contain clauses that become effective upon a change in control of the Company. Upon the occurrence of any of the defined events in the various employment agreements, the Company would be obligated to pay certain amounts to the relevant employees, which vary with the level of the employees’ respective responsibility. 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 multiemployer pension plans, 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 March 31, 2019, 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. 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 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 March 31, 2019 and December 31, 2018, the Company was not aware of any material asserted or unasserted claims in connection with these indemnity obligations. Other Guarantees. In the ordinary course of its business, from time to time, 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 for a one to two year period following substantial completion of a project. Much of the work performed by the Company is evaluated for defects shortly after the work is completed. Warranty claims are not, and have historically not been, material. However, 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. Concentrations of Risk. The Company had approximately 320 customers for the three month period ended March 31, 2019. As of March 31, 2019, three customers each accounted for approximately 23%, 15% and 12%, respectively, of the Company’s consolidated net accounts receivable position, which represents accounts receivable, net, less BIEC. As of December 31, 2018, three customers each accounted for approximately 26%, 18% and 12%, respectively, of the Company’s consolidated net accounts receivable position. In addition, the Company derived 62% and 74%, respectively, of its revenue from its top ten customers for the three month periods ended March 31, 2019 and 2018.

Note 14 – 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 April 2019, an arbitral tribunal award related to a Canadian acquisition was finalized (the “Award”) for approximately $50 million in favor of MasTec. The collectibility of the Award is uncertain and currently under review. Additionally, MasTec has incurred significant arbitration, legal and other costs related to this matter and expects to incur additional costs while pursuing collection of the Award.

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, surety bond providers and in support of performance under certain contracts as well as certain obligations associated with the Company’s equity investments, 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 March 31, 2019 and December 31, 2018, there were $130.7 million and $128.4 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 March 31, 2019 or December 31, 2018.

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 projects in process. 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 subcontractors and vendors. If the Company fails to perform under a contract or to pay 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 March 31, 2019 and December 31, 2018, outstanding performance and payment bonds approximated $233.1 million and $123.6 million, respectively, and estimated costs to complete projects secured by these bonds totaled $61.3 million and $53.0 million as of March 31, 2019 and December 31, 2018, respectively. These amounts do not include performance and payment bonds associated with the Company’s equity investments.

Investment Arrangements. From time to time, the Company may participate in selected investment or strategic arrangements to expand its operations, customer base or geographic reach, including arrangements that combine the Company’s skills and resources with those of others to allow for the performance of particular projects. 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. The Company also holds a 35% undivided interest in a proportionately consolidated non-controlled Canadian contractual joint venture that was underway when the Company acquired Pacer in 2014, whose sole activity involves the construction of a bridge, a business in which the Company does not otherwise engage. This joint venture, which is managed by a third party, and for which the Company has minimal direct construction involvement, automatically terminates upon completion of the project. 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 March 31, 2019, the Company was not aware of circumstances that would reasonably lead to material future claims against it in connection with these arrangements. Included in the Company’s cash balances as of March 31, 2019 and December 31, 2018 are amounts held by entities that are proportionately consolidated totaling $26.7 million and $11.8 million, respectively. These amounts are available to support the operations of those entities, but are not available for the Company’s other operations. Advances on project work associated with the Company’s proportionately consolidated contractual joint ventures, which are reflected within other current liabilities, totaled $3.4 million and $7.0 million as of March 31, 2019 and December 31, 2018.

The Company has other investment 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 details regarding the Company’s other investment 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 March 31, 2019 and December 31, 2018, MasTec’s liability for unpaid claims and associated expenses, including incurred but not reported losses related to these policies, totaled $112.8 million and $108.9 million, respectively, of which $73.1 million and $70.8 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 $3.1 million and $2.9 million as of March 31, 2019 and December 31, 2018, 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 $67.6 million as of both March 31, 2019 and December 31, 2018. Outstanding surety bonds related to self-insurance programs amounted to $34.8 million as of both March 31, 2019 and December 31, 2018. In addition, cash collateral deposited with insurance carriers, which is included within other long-term assets, amounted to $1.6 million for these policies as of both March 31, 2019 and December 31, 2018.

Employment Agreements. The Company has employment agreements with certain executives and other employees, which provide for compensation and certain other benefits and for severance payments under certain circumstances. Certain employment agreements also contain clauses that become effective upon a change in control of the Company. Upon the occurrence of any of the defined events in the various employment agreements, the Company would be obligated to pay certain amounts to the relevant employees, which vary with the level of the employees’ respective responsibility.

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 multiemployer pension plans, 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 March 31, 2019, 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. 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 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 March 31, 2019 and December 31, 2018, the Company was not aware of any material asserted or unasserted claims in connection with these indemnity obligations.

Other Guarantees. In the ordinary course of its business, from time to time, 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 for a one to two year period following substantial completion of a project. Much of the work performed by the Company is evaluated for defects shortly after the work is completed. Warranty claims are not, and have historically not been, material. However, 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.

Concentrations of Risk. The Company had approximately 320 customers for the three month period ended March 31, 2019. As of March 31, 2019, three customers each accounted for approximately 23%, 15% and 12%, respectively, of the Company’s consolidated net accounts receivable position, which represents accounts receivable, net, less BIEC. As of December 31, 2018, three customers each accounted for approximately 26%, 18% and 12%, respectively, of the Company’s consolidated net accounts receivable position. In addition, the Company derived 62% and 74%, respectively, of its revenue from its top ten customers for the three month periods ended March 31, 2019 and 2018.