MasTec (MTZ) 10-Q 30 Apr 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 24, 2018
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Entity Registrant Name	MASTEC INC
Trading Symbol	MTZ
Entity Central Index Key	15,615
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		80,467,691

Condensed Unaudited Consolidate

Condensed Unaudited Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenue		$ 1,396,834	$ 1,158,184
Costs of revenue, excluding depreciation and amortization		1,237,299	971,134
Depreciation and amortization		49,940	42,904
General and administrative expenses		63,622	64,781
Interest expense, net		17,058	12,597
Equity in earnings of unconsolidated affiliates		(5,585)	(1,646)
Other (income) expense, net		(3,089)	429
Income before income taxes		37,589	67,985
Provision for income taxes		(11,126)	(27,358)
Net income		26,463	40,627
Net loss attributable to non-controlling interests		(97)	(343)
Net income attributable to MasTec, Inc.	[1]	$ 26,560	$ 40,970
Earnings per share (Note 2):
Basic earnings per share (in dollars per share)		$ 0.33	$ 0.51
Basic weighted average common shares outstanding		81,150	80,697
Diluted earnings per share (in dollars per share)		$ 0.32	$ 0.50
Diluted weighted average common shares outstanding		82,221	82,157
[1]	Calculated as total net income less amounts attributable to non-controlling interests.

Condensed Unaudited Consolidat3

Condensed Unaudited Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 26,463	$ 40,627
Other comprehensive income:
Foreign currency translation (losses) gains, net of tax	(523)	1,178
Unrealized gains on equity investee activity, net of tax	7,716	636
Comprehensive income	33,656	42,441
Comprehensive loss attributable to non-controlling interests	(97)	(343)
Comprehensive income attributable to MasTec, Inc.	$ 33,753	$ 42,784

Condensed Unaudited Consolidat4

Condensed Unaudited Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 40,235	$ 40,326
Accounts receivable, net (Note 5)	1,705,126	1,598,015
Inventories, net	80,483	76,992
Prepaid expenses	54,077	101,270
Other current assets	27,674	35,763
Total current assets	1,907,595	1,852,366
Property and equipment, net	709,806	706,506
Goodwill, net	1,145,434	1,137,738
Other intangible assets, net	187,442	191,142
Other long-term assets	204,071	178,824
Total assets	4,154,348	4,066,576
Current liabilities:
Current portion of long-term debt	86,558	87,866
Accounts payable	457,832	377,954
Accrued salaries and wages	78,118	89,087
Other accrued expenses	137,063	148,971
Billings in excess of costs and earnings	215,707	194,494
Other current liabilities	72,062	65,455
Total current liabilities	1,047,340	963,827
Long-term debt	1,343,549	1,280,706
Deferred income taxes	197,275	204,518
Other long-term liabilities	191,987	184,172
Total liabilities	2,780,151	2,633,223
Commitments and contingencies (Note 14)
Equity
Preferred stock, $1.00 par value: authorized shares - 5,000,000; issued and outstanding shares – none	0	0
Common stock, $0.10 par value: authorized shares - 145,000,000; issued shares - 91,063,699 and 90,935,584 (including 1,523,484 and 1,421,041 of unvested stock awards) as of March 31, 2018 and December 31, 2017, respectively	9,106	9,094
Capital surplus	779,449	775,387
Retained earnings	885,277	857,154
Accumulated other comprehensive loss	(56,519)	(63,712)
Treasury stock, at cost: 10,171,531 and 8,132,811 shares as of March 31, 2018 and December 31, 2017, respectively	(245,573)	(147,124)
Total MasTec, Inc. shareholders’ equity	1,371,740	1,430,799
Non-controlling interests	2,457	2,554
Total equity	1,374,197	1,433,353
Total liabilities and equity	$ 4,154,348	$ 4,066,576

Condensed Unaudited Consolidat5

Condensed Unaudited Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, shares authorized	145,000,000	145,000,000
Common stock, shares issued	91,063,699	90,935,584
Treasury stock, shares	10,171,531	8,132,811
Restricted Stock Awards [Member] | Common Stock [Member]
Unvested stock awards (in shares)	1,523,484	1,421,041

Condensed Unaudited Consolidat6

Condensed Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income	$ 26,463	$ 40,627
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	49,940	42,904
Non-cash interest expense, net	725	870
Non-cash stock-based compensation expense	3,182	3,773
(Benefit from) provision for deferred income taxes	(7,243)	8,403
Equity in earnings of unconsolidated affiliates	(5,585)	(1,646)
Gains on sales of assets, net, including fixed assets held-for-sale	(2,758)	(57)
Other non-cash items, net	544	288
Changes in assets and liabilities, net of acquisitions:
Accounts receivable, net	(97,240)	73,723
Inventories	(651)	21,404
Other assets, current and long-term portion	55,033	2,190
Accounts payable and accrued expenses	26,351	(74,121)
Billings in excess of costs and earnings	16,888	19,612
Book overdrafts	6,123	(2,187)
Other liabilities, current and long-term portion	11,729	18,390
Net cash provided by operating activities	83,501	154,173
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	(4,329)	0
Capital expenditures	(22,545)	(28,901)
Proceeds from sale of property and equipment	5,382	511
Payments for other investments	(14,779)	(53,347)
Proceeds from other investments	5,415	12,118
Net cash used in investing activities	(30,856)	(69,619)
Cash flows from financing activities:
Proceeds from credit facilities	816,888	361,743
Repayments of credit facilities	(747,099)	(447,112)
Repayments of other borrowings	(14,612)	(1,499)
Payments of capital lease obligations	(18,112)	(12,912)
Repurchase of common stock	(90,880)	0
Distributions to non-controlling interests	(559)	(1,280)
Proceeds from stock-based awards, net	916
Payments for stock-based awards, net		(761)
Other financing activities	0	(5,973)
Net cash used in financing activities	(53,458)	(107,794)
Effect of currency translation on cash	722	160
Net decrease in cash and cash equivalents	(91)	(23,080)
Cash and cash equivalents - beginning of period	40,326	38,767
Cash and cash equivalents - end of period	40,235	15,687
Supplemental cash flow information:
Interest paid	21,355	18,023
Income tax (refunds) payments, net	(28,738)	1,772
Supplemental disclosure of non-cash information:
Equipment acquired under capital lease and financing arrangements	25,755	33,916
Accrued capital expenditures	4,629	1,029
Earn-Out Liabilities [Member]
Supplemental disclosure of non-cash information:
Additions to acquisition-related contingent consideration	$ 4,161	$ 0

Business, Basis of Presentation

Business, Basis of Presentation and Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Business, Basis of Presentation and Significant Accounting Policies	Note 1 – Business, Basis of Presentation and Significant Accounting Policies Nature of the Business MasTec, Inc. (collectively with its subsidiaries, “MasTec” or the “Company”) is a leading infrastructure construction company operating mainly throughout North America across a range of industries. The Company’s primary activities include the engineering, building, installation, maintenance and upgrade of communications, energy and utility infrastructure, such as: wireless, wireline/fiber, install-to-the-home and customer fulfillment activities; petroleum and natural gas pipeline infrastructure; electrical utility transmission and distribution; power generation; heavy civil; and industrial infrastructure. MasTec’s customers are primarily in these industries. MasTec reports its results under five reportable segments: (1) Communications; (2) Oil and Gas; (3) Electrical Transmission; (4) Power Generation and Industrial; and (5) Other. 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, 2017 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, 2017 contained in the Company’s 2017 Annual Report on Form 10-K (the “ 2017 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. 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. All significant intercompany balances and transactions have been eliminated in consolidation. Other parties’ interests in entities that MasTec consolidates 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 for 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. Income or loss from these investments is recorded as a separate line item in the statements of operations. Intercompany profits or losses associated with the Company’s equity method investments are eliminated until realized by the investee in transactions with third parties. For equity investees in which the Company has an undivided interest in the assets, liabilities and profits or losses of an unincorporated entity, but the Company does not exercise control over the entity, the Company consolidates its proportional interest in the accounts of the entity. Equity investments, other than those accounted for as equity method investments or those that are consolidated, are measured at fair value if their fair values are readily determinable. Equity investments that do not have readily determinable fair values are measured at cost, adjusted for changes from observable market transactions, less impairment. Realized and unrealized gains or losses related to equity investments are recognized in other income or expense. Management determines whether each business entity in which it has equity interests, debt, or other investments constitutes a variable interest entity (“VIE”) based on the nature and characteristics of such arrangements. If an investment arrangement is determined to be a VIE, then management determines if the Company is the VIE’s primary beneficiary by evaluating several factors, including the Company’s: (i) risks and responsibilities; (ii) ownership interests; (iii) decision making powers; and (iv) financial interests, among other factors. If management determines the Company is the primary beneficiary of a VIE, then it would be consolidated, and other parties’ interests in the VIE would be accounted for as non-controlling interests. 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. As of March 31, 2018 , the Company determined that certain of its investment arrangements were VIEs; however, because it does not have the power to direct the primary activities that most significantly impact the economic performance of these VIEs, the Company is not the primary beneficiary, and accordingly, has not consolidated these VIEs. 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 their local currency as their functional currency. Currency gains or losses resulting from transactions executed in currencies other than the functional currency are included in other income or expense, net. In these condensed unaudited consolidated financial statements, “$” means U.S. dollars unless otherwise noted. Management Estimates The preparation of consolidated financial statements in accordance with U.S. GAAP requires the use of estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. These estimates are based on historical experience and various other assumptions, the results of which form the basis of making judgments about the Company’s operating results and the carrying values of assets and liabilities that are not readily apparent from other sources. 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 project-related depreciation, in particular, on construction contracts accounted for under the cost-to-cost method, for which the recorded amounts require estimates of costs to complete and the amount of variable consideration included in the contract transaction price; allowances for doubtful accounts; fair value estimates, including those related to business acquisitions, valuations of goodwill and intangible assets, acquisition-related contingent consideration and equity investments; asset lives used in computing depreciation and amortization; fair values of financial instruments; self-insurance liabilities; other accruals and allowances; income taxes; and the estimated effects of litigation and other contingencies. While management believes that such estimates are reasonable when considered in conjunction with the Company’s consolidated financial position and results of operations taken as a whole, actual results could differ materially from those estimates. Significant Accounting Policies Revenue Recognition The Company adopted the requirements of Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers , which is also referred to as Accounting Standards Codification (“ASC”) Topic 606 (“Topic 606”), under the modified retrospective transition approach effective January 1, 2018, with application to all existing contracts that were not substantially completed as of January 1, 2018. The difference between the recognition criteria under Topic 606 and the Company’s previous revenue recognition practices under the previous revenue recognition guidance, ASC Topic 605-35, was recognized through a cumulative effect adjustment of approximately $2 million that was made to the opening balance of retained earnings as of January 1, 2018. Consistent with the modified retrospective transition approach, the comparative 2017 prior period was not adjusted to conform to the current period presentation. Under Topic 606, revenue is recognized when control of promised goods and services is transferred to customers, and the amount of revenue recognized reflects the consideration to which an entity expects to be entitled in exchange for the goods and services transferred. The adoption of Topic 606 did not have, and is not expected to have, a material effect on the timing or amount of revenue recognized as compared with the Company’s previous revenue recognition practices. Revenue is recognized by the Company primarily over time utilizing the cost-to-cost measure of progress for fixed price contracts and certain master service and other service agreements, consistent with the Company’s previous revenue recognition practices. Under Topic 606, the cost-to-cost measure of progress best depicts the transfer of control of goods or services to the customer for these contracts. Contracts. The Company derives revenue primarily from construction projects performed: i) under master and other service agreements, which provide a menu of available services in a specific geographic territory that are utilized on an as-needed basis, and are typically priced using time and materials or a fixed price per unit basis; or ii) under contracts for specific projects requiring the construction and installation of an entire infrastructure system or specified units within an infrastructure system, which are subject to multiple pricing options, including fixed price, unit price, time and materials, or cost plus a markup. Revenue derived from master service and other service agreements totaled 41% and 46% of consolidated revenue for the three month periods ended March 31, 2018 and 2017 , respectively. Revenue from fixed price contracts provides for a fixed amount of revenue for the entire project. Revenue from these contracts, as well as for certain projects pursuant to master and other service agreements, is recognized over time using the cost-to-cost measure of progress. For these contracts, the cost-to-cost measure of progress best depicts the continuous transfer of control of goods or services to the customer. Such contracts provide that the customer accept completion of progress to date and compensate the Company for services rendered. For certain of the Company’s master service and other service agreements, under which it performs installation and maintenance services, primarily for install-to-the-home service providers in its Communications segment, revenue is recognized at a point in time. This is generally when the work order has been fulfilled and control has been transferred to the customer, which is typically the same day the work order is initiated. Substantially all of the Company’s other revenue is recognized over time. Contract costs include all direct materials, labor and subcontracted costs, as well as indirect costs related to contract performance, such as indirect labor, supplies, tools, repairs and the operational costs of capital equipment. The cost estimation process for recognizing revenue over time under the cost-to-cost method is based on the professional knowledge and experience of the Company’s project managers, engineers and financial professionals. Management reviews estimates of total contract transaction price and total project costs on an ongoing basis. Changes in job performance, job conditions and management’s assessment of expected variable consideration are factors that influence estimates of the total contract transaction price, total costs to complete those contracts and profit recognition. Changes in these factors could result in revisions to revenue and costs of revenue in the period in which the revisions are determined on a prospective basis, which could materially affect the Company’s consolidated results of operations for that period. Provisions for losses on uncompleted contracts are recorded in the period in which such losses are determined. Revenue recognized for the three month period ended March 31, 2018 from performance obligations satisfied, or work completed, in previous periods totaled approximately $44.3 million . Under the typical payment terms of master and other service agreements and fixed price contracts, the customer makes progress payments based on quantifiable measures of performance by the Company as defined by each specific agreement. Progress payments, generally net of amounts retained, are paid by the customer over the duration of the contract. For install-to-the-home contracts, work orders are billed and paid as completed. Amounts billed and due from customers, as well as the amount of contract assets, are classified within accounts receivable, net, in the consolidated balance sheets. See Note 5 - Accounts Receivable, Net, and Contract Assets and Liabilities for related discussion. Amounts expected to be collected beyond one year are classified as other long-term assets. Performance Obligations. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer, and is the unit of account under Topic 606. The transaction price of a contract is allocated to each distinct performance obligation and recognized as revenue when or as the performance obligation is satisfied. The Company’s contracts often require significant integration services, and even when delivering multiple distinct services, are generally accounted for as a single performance obligation. Contract amendments and change orders are generally not distinct from the existing contract due to the significant integration service provided in the context of the contract, and are accounted for as a modification of the existing contract and performance obligation. The majority of the Company’s performance obligations are completed within one year. When more than one contract is entered into with a customer on or close to the same date, the Company evaluates whether those contracts should be combined and accounted for as a single contract as well as whether those contracts should be accounted for as more than one performance obligation. This evaluation requires significant judgment and is based on the facts and circumstances of the various contracts, which could change the amount of revenue and profit recognition in a given period depending upon the outcome of the evaluation. Remaining performance obligations represent the amount of unearned transaction prices for fixed price contracts and open purchase orders or work orders under master and other service agreements for which work is wholly or partially unperformed. As of March 31, 2018 , the amount of the Company’s remaining performance obligations was $5.4 billion . The Company expects to recognize approximately $3.9 billion of its remaining performance obligations as revenue in 2018, with the remainder recognized primarily in 2019. Variable Consideration. Transaction pricing for the Company’s contracts may include variable consideration, which is comprised of items such as change orders, claims, incentives and liquidated damages. Management estimates variable consideration for a performance obligation utilizing estimation methods that best predict the amount of consideration to which the Company will be entitled. Variable consideration is included in the estimated transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. Management’s estimates of variable consideration and determination of whether to include estimated amounts in transaction price are based largely on engineering studies and legal opinions, past practices with the customer, specific discussions, correspondence or preliminary negotiations with the customer and all other relevant information that is reasonably available. The effect of variable consideration on the transaction price of a performance obligation is typically recognized as an adjustment to revenue on a cumulative catch-up basis. To the extent unapproved change orders, claims and liquidated damages reflected in transaction price are not resolved in the Company’s favor, or to the extent incentives reflected in transaction price are not earned, there could be reductions in, or reversals of, previously recognized revenue. As of March 31, 2018 and December 31, 2017 , the Company included approximately $280 million and $146 million , respectively, of change orders and/or claims in the transaction price for certain contracts that were in the process of being resolved in the normal course of business, including through negotiation, arbitration and other proceedings. These transaction price adjustments are included within costs and earnings in excess of billings or accounts receivable, net, as appropriate. As of March 31, 2018 and December 31, 2017 , these change orders and/or claims were primarily related to certain large long-haul pipeline construction projects in the Oil and Gas segment that are expected to reach substantial completion in the coming months. The Company actively engages with its customers to complete the final approval process, and generally expects these processes to be completed within one year. Amounts ultimately realized upon final acceptance by customers could be higher or lower than such estimated amounts. Recently Issued Accounting Pronouncements See the revenue recognition discussion within Significant Accounting Policies above, and the recent accounting pronouncements discussion below, for information pertaining to the effects of recently adopted and other recent accounting pronouncements, as updated from the discussion in the Company’s 2017 Form 10-K. Accounting Pronouncements Adopted in 2018 In August 2016, the Financial Accounting Standards Board (“FASB”) issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”) to reduce diversity in practice by providing guidance on the classification of certain cash receipts and payments in the statement of cash flows . This ASU, which the Company adopted as of January 1, 2018, is effective on a retrospective basis, and will result in the reclassification of certain types of activity in the consolidated statement of cash flows, including the reclassification of $12 million of second quarter 2017 acquisition-related contingent consideration payments in excess of acquisition date liabilities from financing to operating cash flows. Additionally, in connection with the adoption of this ASU, the Company elected to account for distributions received from equity method investees using the nature of distributions approach, under which distributions are classified based on the nature of the activity that generated them. The other provisions of this ASU did not have a material effect on the Company’s consolidated financial statements. In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2016-01”), which was further amended in February and in March 2018 by ASU 2018-03, Technical Corrections and Improvements to Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2018-03”) and ASU 2018-04, Investments - Debt Securities (Topic 320) and Regulated Operations (Topic 980): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 117 and SEC Release No. 33-9273 (“ASU 2018-04”) to clarify certain aspects of ASU 2016-01 and to update Securities and Exchange Commission (“SEC”) interpretive guidance in connection with the provisions of ASU 2016-01. These ASUs provide guidance for the recognition, measurement, presentation and disclosure of financial assets and financial liabilities, including equity investments other than those accounted for under the equity method of accounting or those that are consolidated . Equity investments within the scope of these ASUs are required to be measured at fair value with changes in fair value recognized in net income. Equity investments that do not have readily determinable fair values are permitted to be measured at cost, less any impairment, plus or minus any changes resulting from observable price changes for identical or similar investments of the same issuer (the “measurement alternative”). The Company adopted these ASUs as of January 1, 2018, which was applicable to the Company on a prospective basis for its equity investments as they do not have readily determinable fair values, and for which the Company elected to utilize the measurement alternative. The adoption of these ASUs will result in volatility in other income (expense), net, upon the occurrence of any observable price changes or impairments related to its equity investments. For further information pertaining to the Company’s equity investments, see Note 4 - Fair Value of Financial Instruments. The other provisions of these ASUs did not have a material effect on the Company’s consolidated financial statements. Other Recent Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016-02”). ASU 2016-02 provides revised guidance for lease accounting and related disclosure requirements, including a requirement for lessees to recognize right-of use assets and lease liabilities on the balance sheet for leases with durations greater than twelve months. ASU 2016-02 is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted. Modified retrospective application is required for all leases existing as of, or entered into after, the beginning of the earliest comparative period presented in the consolidated financial statements, with certain practical expedients available. The Company will adopt ASU 2016-02 as of January 1, 2019, and expects to utilize the expedients permitted under ASU 2016-02, which allow entities to retain the classification of lease contracts existing as of the date of adoption. The Company is continuing to assess the potential effects of this ASU, which have not yet been quantified, on its consolidated financial statements, business processes, systems and controls. The Company’s assessment, which it expects to substantially complete in the fourth quarter of 2018, includes a detailed review of representative lease contracts at each of the Company’s business units and a comparison of its historical accounting policies and practices to the new standard. Based on the Company’s progress in reviewing its leasing arrangements across all of its business units, the Company expects to recognize incremental lease assets and liabilities on its consolidated balance sheets upon adoption of the standard. This ASU is not expected to have a material effect on the amount of expense recognized in connection with the Company’s current leasing arrangements as compared to current practice, however, based on the Company’s preliminary review of its lease contracts to date, it anticipates that the amount of incremental lease assets and lease liabilities to be recognized upon adoption of this ASU will be material. The Company’s expectations may change as its assessment progresses. For information about the Company’s future lease commitments as of December 31, 2017, see Note 8 - Lease Obligations, in the Company’s 2017 Form 10-K.

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share	Note 2 – Earnings Per Share Basic earnings or loss per share is computed by dividing net income or loss attributable to MasTec by the weighted average number of common shares outstanding for the period, which excludes non-participating unvested restricted share awards. Diluted earnings per share is computed by dividing net income or loss attributable to MasTec by the weighted average number of fully diluted shares, as calculated under the treasury stock method, which includes the potential effect of dilutive common stock equivalents, such as issued but unvested restricted shares. If the Company reports a loss, rather than income, the computation of diluted loss per share excludes the effect of dilutive common stock equivalents, as their effect would be anti-dilutive. The following table provides details underlying the Company’s earnings per share calculations for the periods indicated (in thousands): For the Three Months Ended March 31 2018 2017 Net income attributable to MasTec: Net income - basic and diluted (a) $ 26,560 $ 40,970 Weighted average shares outstanding: Weighted average shares outstanding - basic 81,150 80,697 Dilutive common stock equivalents 1,071 1,460 Weighted average shares outstanding - diluted 82,221 82,157 Additional information: Weighted average anti-dilutive common stock equivalents (b) — 19 (a) Calculated as total net income less amounts attributable to non-controlling interests. (b) Represents anti-dilutive common stock equivalents as calculated under the treasury stock method. During the three month period ended March 31, 2018 , the Company repurchased approximately 2.0 million shares of its common stock, as discussed in Note 11 - Equity. The effect of these repurchases on the Company’s weighted average shares outstanding for the three month period ended March 31, 2018 was minimal due to the timing of the repurchases, which occurred in the latter part of the quarter. In future quarters, these share repurchases will be fully reflected in the total number of weighted average shares outstanding for the respective quarter to date periods.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	Note 3 - Goodwill and Other Intangible Assets The following table provides balances for goodwill by reportable segment as of March 31, 2018 (in millions): Communications Oil and Gas Electrical Transmission Power Generation and Industrial Total Goodwill Goodwill, gross $ 466.2 $ 460.4 $ 149.9 $ 141.8 $ 1,218.3 Accumulated impairment loss — (72.9 ) — — (72.9 ) Goodwill, net $ 466.2 $ 387.5 $ 149.9 $ 141.8 $ 1,145.4 For the three month period ended March 31, 2018 , additions to goodwill totaled $9.8 million from new business combinations and reductions to goodwill, net, from measurement period adjustments related to the Company’s 2017 acquisitions totaled $0.6 million . Measurement period adjustments consisted primarily of a decrease in deferred tax liabilities, offset by increases in estimated earn-out liabilities, working capital adjustments and a decrease in intangible assets. For the three month period ended March 31, 2018 , currency translation effects related to goodwill and accumulated impairment losses totaled approximately $3.4 million of losses and $1.9 million of gains, respectively, and for the three month period ended March 31, 2017 , totaled $1.1 million of gains and $0.6 million of losses, respectively. The following table provides a reconciliation of changes in other intangible assets, net, for the period indicated (in millions): Other Intangible Assets Non-Amortizing Amortizing Trade Names Pre-Qualifications Customer Relationships and Backlog Other (a) Total Other intangible assets, gross, as of December 31, 2017 $ 34.5 $ 77.6 $ 223.0 $ 21.8 $ 356.9 Accumulated amortization (152.4 ) (13.4 ) (165.8 ) Other intangible assets, net, as of December 31, 2017 $ 34.5 $ 77.6 $ 70.6 $ 8.4 $ 191.1 Additions from new business combinations — — 2.9 0.3 3.2 Measurement period adjustments (b) — — — (0.7 ) (0.7 ) Amortization expense (4.5 ) (0.4 ) (4.9 ) Currency translation adjustments — (1.2 ) (0.1 ) — (1.3 ) Other intangible assets, net, as of March 31, 2018 $ 34.5 $ 76.4 $ 68.9 $ 7.6 $ 187.4 (a) Consists principally of trade names and non-compete agreements. (b) Represents adjustments to preliminary estimates of the fair values of intangible assets acquired within the measurement period for the Company’s 2017 acquisitions. Amortization expense associated with intangible assets for the three month periods ended March 31, 2018 and 2017 totaled $4.9 million and $4.1 million , respectively. 2018 Acquisitions. During the first quarter of 2018 , MasTec acquired all of the equity interests in: (i) a construction management firm specializing in steel building systems ; and (ii) a wind turbine services company , both of which are included in the Company’s Power Generation and Industrial segment. The aggregate purchase price for these entities was composed of approximately $6.1 million in cash and estimated earn-out liabilities totaling $1.5 million as of March 31, 2018 . Determination of the estimated fair values of the net assets acquired and the estimated earn-out liabilities for these acquisitions was preliminary as of March 31, 2018 , and further adjustments to these estimates may occur. 2017 Acquisitions. During 2017 , MasTec completed three acquisitions, which included all of the equity interests in: (i) a wireline/fiber deployment construction contractor , which is included in the Company’s Communications segment; (ii) a heavy civil construction services company , which is included in the Company’s Power Generation and Industrial segment, and (iii) an oil and gas pipeline equipment company , which is included in the Company’s Oil and Gas segment. Determination of the estimated fair values of the net assets acquired and the estimated earn-out liabilities for these acquisitions was preliminary as of March 31, 2018 , and further adjustments to these estimates may occur. The following table summarizes the estimated fair values of consideration paid and net assets acquired as of the respective dates of acquisition, as adjusted (in millions): Acquisition consideration: 2017 Cash $ 120.3 Fair value of contingent consideration (earn-out liability) 96.3 Total consideration transferred $ 216.6 Identifiable assets acquired and liabilities assumed: Current assets, primarily composed of accounts receivable and $2.8 million of cash acquired $ 43.8 Property and equipment and other long-term assets 57.2 Amortizing intangible assets 28.1 Current liabilities, including current portion of capital lease obligations and long-term debt (29.4 ) Long-term debt, including capital lease obligations (9.9 ) Deferred income taxes and other long-term liabilities (10.6 ) Total identifiable net assets $ 79.2 Goodwill $ 137.4 Total net assets acquired, including goodwill $ 216.6 Amortizing intangible assets related to the 2017 acquisitions are primarily composed of customer relationships, backlog and other amortizing intangible assets, which had weighted average lives, as adjusted, of approximately 11 years, 4 years and 6 years, respectively, and a weighted average life of 10 years in total, and will be amortized in a manner consistent with the pattern in which the related benefits are expected to be consumed. The goodwill balances for the respective acquisitions represent the estimated value of each acquired company’s geographic presence in key markets, its assembled workforce and management team industry-specific project management expertise, as well as synergies expected to be achieved from the combined operations of the acquired companies and MasTec. Approximately $90 million of the acquired goodwill balance as of March 31, 2018 is expected to be tax deductible. The contingent consideration included in the table above equals the acquired companies’ earnings before interest, taxes, depreciation and amortization (“EBITDA”) above certain thresholds, if applicable, for a period of five years, as set forth in the respective purchase agreements, which amounts are payable annually. The fair values of the earn-out liabilities were estimated using income approaches such as discounted cash flows or option pricing models and incorporate significant inputs not observable in the market. Key assumptions in the estimated valuations include the discount rate and probability-weighted EBITDA projections. Significant changes in any of these assumptions could result in a significantly higher or lower potential earn-out liability. As of March 31, 2018 , the range of potential undiscounted earn-out liabilities for the 2017 acquisitions was estimated to be between $14 million and $188 million ; however, there is no maximum payment amount . For the three month periods ended March 31, 2018 and 2017 , unaudited supplemental pro forma revenue totaled approximately $1,400.3 million and $1,220.2 million , respectively, and unaudited supplemental pro forma net income totaled approximately $24.1 million and $42.6 million , respectively. These unaudited pro forma financial results represent the results of operations of the companies acquired as if the acquired companies had been consolidated as of the beginning of the year prior to their acquisition, and are provided for illustrative purposes only. These unaudited pro forma financial results do not purport to be indicative of the actual results that would have been achieved by the combined companies for the periods indicated, or of the results that may be achieved by the combined companies in the future. The Company’s unaudited pro forma financial results were prepared by adjusting the historical results of MasTec to include the historical results of the acquired businesses described above, and then adjusted (i) to remove acquisition costs; (ii) to increase amortization expense resulting from the acquired intangible assets; (iii) to increase interest expense as a result of the cash consideration paid; (iv) to reduce interest expense from debt repaid upon acquisition; and (iv) to eliminate the effects of intercompany transactions. These unaudited pro forma financial results do not include adjustments to reflect other cost savings or synergies that may have resulted from these acquisitions. Future results may vary significantly due to future events and transactions, as well as other factors, many of which are beyond the Company’s control. For the three month period ended March 31, 2018 , acquisition-related results included in the Company’s consolidated results of operations included revenue of approximately $76.8 million and net income of approximately $2.0 million , based on the Company’s consolidated effective tax rate. These acquisition-related results do not include the effects of acquisition costs or interest expense associated with consideration paid for the related acquisitions.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Note 4 – 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, equity investments, deferred compensation plan assets and liabilities, accounts payable and other current liabilities, acquisition-related contingent consideration 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, accounts payable and other current liabilities approximate their fair values. Management believes the carrying values of notes and other receivables, cash collateral deposited with insurance carriers, deferred compensation plan assets and liabilities and outstanding balances on its credit facilities approximate their fair values. Assets and Liabilities Measured at Fair Value on a Recurring Basis As of March 31, 2018 and December 31, 2017 , financial instruments required to be measured at fair value on a recurring basis consisted primarily of acquisition-related contingent consideration, or “earn-out” liabilities, which represents the estimated fair value of future amounts payable for acquisitions of businesses and other interests. Acquisition-related contingent consideration liabilities are based on management estimates and entity-specific assumptions, which are Level 3 inputs, and are evaluated on an ongoing basis. As of March 31, 2018 and December 31, 2017 , the estimated fair value of the Company’s earn-out liabilities totaled $121.4 million and $117.2 million , respectively, of which $23.8 million and $22.6 million , respectively, was included within other current liabilities. The fair value of the Company’s earn-out liabilities is estimated using income approaches such as discounted cash flows or option pricing models and incorporates significant inputs not observable in the market. Key assumptions include the discount rate and probability-weighted EBITDA projections. Significant changes in any of these assumptions could result in a significantly higher or lower potential earn-out liability. As of March 31, 2018 , the range of potential undiscounted earn-out liabilities was estimated to be between $28 million and $214 million ; however, there is no maximum payment amount . Acquisition-related contingent consideration activity consists primarily of additions from new business combinations and acquisitions of other interests; payments; and changes in the expected fair value of future earn-out obligations. Fair value adjustments for earn-out liabilities that relate to circumstances that developed after the date of acquisition are recorded within other income or expense, as appropriate. Fair value adjustments for earn-out liabilities that relate to new information obtained about the facts and circumstances that existed as of the date of acquisition, which are referred to as measurement period adjustments, are recorded to goodwill. For the three month period ended March 31, 2018 , additions to acquisition-related contingent consideration from new business combinations totaled approximately $1.5 million and additions from measurement period adjustments totaled approximately $2.7 million . Other acquisition-related contingent consideration activity was de minimis in both the three month periods ended March 31, 2018 and 2017 . 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 equity investments, life insurance assets, long-lived assets, goodwill, other intangible assets and debt. As of both March 31, 2018 and December 31, 2017 , the gross carrying amount of the Company’s 4.875% Senior Notes totaled $400 million . As of March 31, 2018 and December 31, 2017 , the estimated fair value of the 4.875% Senior Notes, based on Level 1 inputs, totaled $400.0 million and $410.0 million , respectively. Equity Investments The Company’s equity investments as of March 31, 2018 include: (i) the Company’s 33% equity interests in Trans-Pecos Pipeline, LLC (“TPP”) and Comanche Trail Pipeline, LLC (“CTP,” and together with TPP, the “Waha JVs”), which are accounted for as equity method investments; (ii) a $15 million investment in Cross Country Infrastructure Services, Inc. (“CCI”); (iii) the Company’s interests in its proportionately consolidated non-controlled contractual joint ventures; (iv) the Company’s equity interests in Pensare Acquisition Corp. (“Pensare”); and (v) certain other equity investments. See below and Note 15 - Related Party Transactions. The fair values of the Company’s equity investments are not readily determinable. The Company’s equity investments, other than those accounted for as equity method investments or those that are proportionately consolidated, are measured at cost, adjusted for changes from observable market transactions, less impairment (“adjusted cost basis”), with realized and unrealized gains or losses recognized in other income or expense. Fair value measurements for the Company’s equity investments are classified within Level 3 in the fair value hierarchy based on the nature of the fair value inputs. For the three month period ended March 31, 2018 , the Company was not aware of any observable market transactions related to, or impairments of, its equity investments. The aggregate carrying value of the Company’s equity investments as of March 31, 2018 and December 31, 2017 totaled approximately $163 million and $141 million , respectively, including approximately $18 million of equity investments measured on an adjusted cost basis as of both periods. The Waha JVs . The Waha JVs own and operate two pipelines and a header system that transport natural gas to the Mexican border for export. These pipelines, which interconnect with pipelines in Mexico, commenced operations in 2017. For the three month periods ended March 31, 2018 and 2017 , the Company made equity contributions to these joint ventures of approximately $14.8 million and $53.3 million , respectively. In connection with its equity commitments in the Waha JVs, the Company has, in the past, issued letters of credit, of which $19 million were outstanding as of December 31, 2017 . As of March 31, 2018 , there were no letters of credit remaining, and all of the Company’s equity commitments had been satisfied. Equity in earnings related to the Company’s proportionate share of income from the Waha JVs, which is included within the Company’s Other segment, totaled approximately $5.6 million and $1.6 million for the three month periods ended March 31, 2018 and 2017 , respectively. Cumulative undistributed earnings from the Waha JVs totaled $16.8 million as of March 31, 2018 . For the three month period ended March 31, 2018 , the Company received $5.7 million in distributions of earnings from the Waha JVs. The Company’s net investment in the Waha JVs, which differs from its proportionate share of the net assets of the Waha JVs due largely to capitalized investment costs, totaled approximately $144 million and $121 million as of March 31, 2018 and December 31, 2017 , respectively. Certain subsidiaries of MasTec have provided pipeline construction services to the Waha JVs. For the three month period ended March 31, 2018 , revenue recognized in connection with work performed for the Waha JVs, including intercompany eliminations, was de minimis, and for the three month period ended March 31, 2017 , totaled $151.4 million . As of March 31, 2018 and December 31, 2017 , related receivables, net of billings in excess of costs and earnings, totaled $0.2 million and $2.8 million , respectively. TPP and CTP are party to separate non-recourse financing facilities, which are each secured by pledges of the equity interests in the respective entities, as well as a first lien security interest over virtually all of TPP’s and CTP’s assets. The Waha JVs are also party to certain interest rate swaps, which are accounted for as qualifying cash flow hedges. The Company reflects its proportionate share of any unrealized fair market value gains or losses from fluctuations in interest rates associated with these swaps within other comprehensive income or loss, as appropriate. The Company’s proportionate share of unrecognized unrealized activity on these interest rate swaps for the three month periods ended March 31, 2018 and 2017 were gains of approximately $10.1 million and $1.0 million , respectively, or $7.7 million and $0.6 million , net of tax, respectively. Other Investments During the third quarter of 2017, the Company paid $2.0 million for approximately 4% of the common stock of Pensare and warrants to purchase 2.0 million shares of Pensare common stock, which is a special purpose acquisition company focusing on transactions in the telecommunications industry. The shares of common stock purchased by MasTec are not transferable or salable until one year after Pensare successfully completes a business combination transaction, with limited exceptions, as specified in the agreement. The warrants purchased by MasTec are exercisable at a purchase price of $11.50 per share after Pensare successfully completes a business combination. Both the warrants and shares expire and/or are effectively forfeitable if Pensare does not successfully complete a business combination by February 1, 2019. The warrants, which are derivative financial instruments, and the shares, which are measured on an adjusted cost basis, are included within other long-term assets in the Company’s consolidated financial statements as of March 31, 2018 . The fair value of the warrants, as determined based on Level 3 inputs, approximated their initial cost basis as of March 31, 2018 . The fair value of the shares is not readily determinable due to the nature of the restrictions. José R. Mas, MasTec’s Chief Executive Officer, is a director of Pensare. In connection with the 2014 acquisition of Pacer Construction Holdings Corporation and its affiliated operating companies (collectively, “Pacer”), the Company acquired an investment that is in the final stages of being liquidated and is being managed by a receiver. The Company received $5.4 million and $12.1 million of proceeds from the receiver in the three month periods ended March 31, 2018 and 2017 , respectively. The net carrying value, which is included within other current assets, totaled $4.0 million and $9.6 million as of March 31, 2018 and December 31, 2017 , respectively.

Accounts Receivable, Net and Co

Accounts Receivable, Net and Contract Assets and Liabilities	3 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Accounts Receivable, Net and Contract Assets and Liabilities	Note 5 - Accounts Receivable, Net, and Contract Assets and Liabilities The following table provides details of accounts receivable, net of allowance, contract assets (together, “accounts receivable, net”) and contract liabilities as of the dates indicated (in millions): March 31, December 31, Contract billings $ 679.4 $ 683.9 Less allowance for doubtful accounts (9.0 ) (8.2 ) Accounts receivable, net of allowance $ 670.4 $ 675.7 Retainage 301.9 323.1 Costs and earnings in excess of billings 732.8 599.2 Retainage and costs and earnings in excess of billings (together, “contract assets”) $ 1,034.7 $ 922.3 Accounts receivable, net $ 1,705.1 $ 1,598.0 Billings in excess of costs and earnings 215.7 194.5 Accrued project losses 6.7 11.6 Contract liabilities $ 222.4 $ 206.1 Contract assets consist of costs and earnings in excess of billings (“CIEB”) and retainage. CIEB, which is also referred to as work in process, represents the estimated value of unbilled work. Retainage represents a portion of the contract amount that has been billed, but for which the contract allows the customer to retain a portion of the billed amount until final contract settlement (generally, from 5% to 10% of contract billings). Retainage is not considered to be a significant financing component because the intent is to protect the customer. CIEB and retainage amounts are generally classified as current assets within the Company’s consolidated balance sheets. Under certain contracts, the Company may be entitled to receive payments in advance of performing the related contract work. In those instances, the Company recognizes a liability for advance billings in excess of revenue recognized, which is referred to as billings in excess of costs and earnings (“BIEC”). BIEC is not considered to be a significant financing component because it is generally used to meet working capital demands that can be higher in the early stages of a contract. Contract liabilities consist primarily of such BIEC, which are generally classified within current liabilities on the Company’s consolidated balance sheets. If revenue from BIEC is not expected to be recognized within one year, the related amounts are classified as other long-term liabilities. For the three month period ended March 31, 2018 , the Company recognized revenue of approximately $84.8 million related to amounts that were included in BIEC as of December 31, 2017 , resulting primarily from the advancement of physical progress on the respective projects during the period. Contract liabilities also include accrued project losses, which are classified within other current liabilities on the Company’s consolidated balance sheets. Provisions for doubtful accounts for each of the three month periods ended March 31, 2018 and 2017 totaled $0.8 million and $0.5 million , respectively. Retainage, which has been billed, but is not due until completion of performance and acceptance by customers, is expected to be collected within one year. Accounts receivable expected to be collected beyond one year are recorded within other long-term assets. The increase in the CIEB balance for the three month period ended March 31, 2018 was driven largely by long-haul project activity and timing of billings within our Oil and Gas segment. The Company is party to non-recourse financing arrangements in the ordinary course of business, under which certain receivables are settled with the customer’s bank in return for a nominal fee. These arrangements, under which amounts can vary based on levels of activity, interest rates and changes in customer payment terms, improve the collection cycle time of the related receivables. Cash collected from these arrangements is reflected within cash provided by operating activities in the consolidated statements of cash flows. The discount charge, which is included within interest expense, net, totaled approximately $1.9 million and $0.9 million for the three month periods ended March 31, 2018 and 2017 , respectively.

Property and Equipment, Net

Property and Equipment, Net	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Note 6 - Property and Equipment, Net The following table provides details of property and equipment, net, including property and equipment held under capital leases as of the dates indicated (in millions): March 31, December 31, Land $ 4.6 $ 4.6 Buildings and leasehold improvements 26.6 26.7 Machinery and equipment 1,285.8 1,261.9 Office furniture and equipment 156.9 149.9 Construction in progress 15.1 12.5 Total property and equipment $ 1,489.0 $ 1,455.6 Less accumulated depreciation and amortization (779.2 ) (749.1 ) Property and equipment, net $ 709.8 $ 706.5 The gross amount of capitalized internal-use software, which is included within office furniture and equipment, totaled $113.8 million and $109.9 million as of March 31, 2018 and December 31, 2017 , respectively. Capitalized internal-use software, net of accumulated amortization, totaled $25.0 million and $23.5 million as of March 31, 2018 and December 31, 2017 , respectively. Depreciation and amortization expense associated with property and equipment for the three month periods ended March 31, 2018 and 2017 totaled $45.1 million and $38.8 million , respectively.

Debt

Debt	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Debt	Note 7 - Debt The following table provides details of the carrying values of debt as of the dates indicated (in millions): Description Maturity Date March 31, December 31, Senior secured credit facility: February 22, 2022 Revolving loans $ 453.8 $ 377.7 Term loan 391.9 396.9 4.875% Senior Notes March 15, 2023 400.0 400.0 Capital lease obligations, weighted average interest rate of 3.7% In installments through September 1, 2022 187.5 181.2 Other debt obligations Varies 9.2 25.8 Total long-term debt obligations $ 1,442.4 $ 1,381.6 Less unamortized deferred financing costs (12.3 ) (13.0 ) Total debt, net of deferred financing costs $ 1,430.1 $ 1,368.6 Current portion of long-term debt 86.6 87.9 Long-term debt $ 1,343.5 $ 1,280.7 Senior Secured Credit Facility The Company has a senior secured credit facility (the “Credit Facility”). Under the Credit Facility, aggregate borrowing commitments totaled approximately $1.5 billion as of March 31, 2018 , composed of $1.1 billion of revolving commitments and a term loan of approximately $0.4 billion . The term loan is subject to amortization in quarterly principal installments. An initial installment of $3.1 million was paid in December 2017, and for the three month period ended March 31, 2018 , an installment of $5.0 million was paid. Quarterly principal installments on the term loan are subject to adjustment, if applicable, for certain prepayments. As of March 31, 2018 and December 31, 2017 , outstanding revolving loans, which included $112 million and $117 million , respectively, of borrowings denominated in foreign currencies, accrued interest at weighted average rates of approximately 3.98% and 3.69% per annum, respectively. The term loan accrued interest at a rate of 3.50% and 3.07% as of March 31, 2018 and December 31, 2017 , respectively. Letters of credit of approximately $131.7 million and $157.1 million were issued as of March 31, 2018 and December 31, 2017 , respectively. As of March 31, 2018 and December 31, 2017 , letters of credit fees accrued at 0.750% and 0.625% per annum, respectively, for performance standby letters of credit, and at 1.625% and 1.50% per annum, respectively, for financial standby letters of credit. Outstanding letters of credit mature at various dates and most have automatic renewal provisions, subject to prior notice of cancellation. As of March 31, 2018 and December 31, 2017 , availability for revolving loans totaled $514.5 million and $565.2 million , respectively, or up to $514.5 million and $492.9 million , respectively, for new letters of credit. Revolving loan borrowing capacity included $187.7 million and $183.4 million of availability in either Canadian dollars or Mexican pesos as of March 31, 2018 and December 31, 2017 , respectively. The unused facility fee as of March 31, 2018 and December 31, 2017 accrued at a rate of 0.30% and 0.25% , respectively. The Credit Facility is guaranteed by certain subsidiaries of the Company (the “Guarantor Subsidiaries”) and the obligations under the Credit Facility are secured by substantially all of the Company’s and the Guarantor Subsidiaries’ respective assets, subject to certain exceptions. Other Credit Facilities . The Company has other credit facilities that support the working capital requirements of its foreign operations. Borrowings under these credit facilities, which have varying dates of maturity and are generally renewed on an annual basis, are denominated in Canadian dollars. As of both March 31, 2018 and December 31, 2017 , maximum borrowing capacity totaled Canadian $20.0 million , or approximately $15.5 million and $15.9 million , respectively. As of March 31, 2018 and December 31, 2017 , outstanding borrowings totaled approximately $6.4 million and $10.4 million , respectively, and accrued interest at a weighted average rate of approximately 4.2% and 4.0% , respectively. Outstanding borrowings that are not renewed are repaid with borrowings under the Credit Facility. Accordingly, the carrying amounts of the Company’s borrowings under its other credit facilities, which are included within other debt obligations in the table above, are classified within long-term debt in the Company’s consolidated balance sheets. The Company’s other credit facilities are subject to customary provisions and covenants. Debt Guarantees and Covenants The 4.875% Senior Notes are senior unsecured unsubordinated obligations and rank equal in right of payment with existing and future unsubordinated debt, and rank senior in right of payment to existing and future subordinated debt and are fully and unconditionally guaranteed on an unsecured, unsubordinated, joint and several basis by certain of the Company’s existing and future 100%-owned direct and indirect domestic subsidiaries that are each guarantors of the Credit Facility or other outstanding indebtedness. See Note 16 - Supplemental Guarantor Condensed Unaudited Consolidating Financial Information. MasTec was in compliance with the provisions and covenants of its outstanding debt instruments as of March 31, 2018 and December 31, 2017 . Additional Information As of March 31, 2018 and December 31, 2017 , accrued interest payable, which is recorded within other accrued expenses in the consolidated balance sheets, totaled $2.5 million and $7.4 million , respectively. For additional information pertaining to the Company’s debt instruments, including its 4.875% Senior Notes, see Note 7 - Debt in the Company’s 2017 Form 10-K.

Lease Obligations

Lease Obligations	3 Months Ended
	Mar. 31, 2018
Leases [Abstract]
Lease Obligations	Note 8 - Lease Obligations Capital Leases MasTec enters into agreements that provide lease financing for machinery and equipment. The gross amount of assets held under capital leases as of March 31, 2018 and December 31, 2017 , which are included within property and equipment, net, totaled $429.9 million and $418.0 million , respectively. Assets held under capital leases, net of accumulated depreciation, totaled $288.2 million and $277.3 million as of March 31, 2018 and December 31, 2017 , respectively. Operating 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 15 - Related Party Transactions. Rent and related expense for operating leases that have non-cancelable terms in excess of one year totaled approximately $26.9 million and $25.6 million for the three month periods ended March 31, 2018 and 2017 , respectively. The Company also incurred rent and related expense for facilities, vehicles and equipment having original terms of one year or less totaling approximately $91.7 million and $55.1 million for the three month periods ended March 31, 2018 and 2017 , respectively.

Stock-Based Compensation and Ot

Stock-Based Compensation and Other Employee Benefit Plans	3 Months Ended
	Mar. 31, 2018
Share-based Compensation [Abstract]
Stock-Based Compensation and Other Employee Benefit Plans	Note 9 – Stock-Based Compensation and Other Employee Benefit Plans The Company has stock-based compensation plans, under which shares of the Company’s common stock are reserved for issuance. Under all stock-based compensation plans in effect as of March 31, 2018 , including employee stock purchase plans, there were approximately 4.7 million shares available for future grant. Restricted Shares MasTec grants restricted stock awards and restricted stock units (together “restricted shares”) to eligible employees and directors, which are valued based on the closing market share price of MasTec common stock (the “market price”) on the date of grant. During the restriction period, holders of restricted stock awards are entitled to vote the shares. Total unearned compensation related to restricted shares as of March 31, 2018 was approximately $23.0 million , which is expected to be recognized over a weighted average period of approximately 2.2 years. The intrinsic value of restricted shares that vested, which is based on the market price on the date of vesting, totaled $0.1 million and $11.6 million for the three month periods ended March 31, 2018 and 2017 , respectively. Activity, restricted shares: (a) Restricted Per Share Weighted Average Grant Date Fair Value Non-vested restricted shares, as of December 31, 2017 1,448,591 $ 23.29 Granted 111,367 50.83 Vested (2,372 ) 50.60 Canceled/forfeited (6,552 ) 22.23 Non-vested restricted shares, as of March 31, 2018 1,551,034 $ 25.23 (a) Includes 27,550 restricted stock units as of both March 31, 2018 and December 31, 2017 , respectively. Employee Stock Purchase Plans The Company has certain employee stock purchase plans (collectively, “ESPPs”) under which shares of the Company's common stock are available for purchase by eligible employees. The following table provides details pertaining to the Company’s ESPPs for the periods indicated: For the Three Months Ended March 31 2018 2017 Cash proceeds (in millions) $ 1.0 $ 0.8 Common shares issued 25,638 24,026 Weighted average price per share $ 39.99 $ 32.51 Weighted average per share grant date fair value $ 9.79 $ 8.49 Non-Cash Stock-Based Compensation Expense Details of non-cash stock-based compensation expense and related tax effects for the periods indicated were as follows (in millions): For the Three Months Ended March 31 2018 2017 Non-cash stock-based compensation expense $ 3.2 $ 3.8 Income Tax Effects: Income tax effect of non-cash stock-based compensation $ 0.8 $ 1.2 Excess tax benefit from non-cash stock-based compensation (a) $ — $ — (a) Excess tax benefits represent cash flows from tax deductions in excess of the tax effect of compensation expense associated with share-based payment arrangements. For the three month period ended March 31, 2018 , tax benefit s, net of tax deficiencies , related to the vesting of share-based payment awards were de minimis, and, for the three month period ended March 31, 2017 , the Company recognized a tax deficiency , net of tax benefits , of $0.2 million .

Other Retirement Plans

Other Retirement Plans	3 Months Ended
	Mar. 31, 2018
Multiemployer Plans [Abstract]
Other Retirement Plans	Note 10 – Other Retirement Plans Multiemployer Plans. Certain of MasTec’s subsidiaries, including certain subsidiaries in Canada, contribute amounts to multiemployer pension and other multiemployer benefit plans and trusts (“MEPPs”), which are recorded as a component of employee wages and salaries within costs of revenue, excluding depreciation and amortization. Contributions are generally based on fixed amounts per hour per employee for employees covered under these plans. Multiemployer plan contribution rates are determined annually and assessed on a “pay-as-you-go” basis based on union employee payrolls. Union payrolls cannot be determined for future periods because the number of union employees employed at any given time, and the plans in which they participate, vary depending upon the location and number of ongoing projects at a given time and the need for union resources in connection with those projects. Total contributions to multiemployer plans and the related number of employees covered by these plans, including with respect to the Company’s Canadian operations, for the periods indicated were as follows: Multiemployer Plans Covered Employees Contributions (in millions) Low High Pension Other Multiemployer Total For the Three Months Ended March 31: 2018 2,018 2,612 $ 11.4 $ 2.0 $ 13.4 2017 550 3,669 $ 3.7 $ 2.6 $ 6.3 The fluctuations in the number of employees covered under multiemployer plans and related contributions in the table above are primarily related to higher levels of union resource-based project activity within the Company’s oil and gas operations.

Equity

Equity	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Equity	Note 11 – Equity Share Activity During the three month period ended March 31, 2018 , the Company repurchased approximately 2.0 million shares of its common stock for an aggregate purchase price of $98.4 million , of which approximately $8 million was settled in April 2018, under a now completed share repurchase program that was established in 2016. Subsequently, in March 2018, the Company’s Board of Directors authorized a new $100 million share repurchase program (the “2018 Share Repurchase Program”). There were no share repurchases under the 2018 Share Repurchase Program during the first quarter of 2018 ; however, in April 2018, the Company repurchased approximately 0.6 million shares of its common stock for an aggregate purchase price of $24.5 million under this program. Under the 2018 Share Repurchase Program, which does not have an expiration date, the Company may repurchase shares of its common stock from time to time in open market transactions or in privately-negotiated transactions in accordance with applicable securities laws. The timing and the amount of any repurchases will be determined based on market conditions, legal requirements, cash flow and liquidity needs and other factors. The share repurchase program may be modified or suspended at any time at the Company’s discretion. Share repurchases, which are recorded at cost and are held in the Company’s treasury, are funded with available cash or with availability under the Credit Facility. Accumulated Other Comprehensive Loss Accumulated other comprehensive loss is composed of unrealized foreign currency gains and losses from fluctuations in foreign currency exchange rates of the Company’s foreign subsidiaries with a functional currency other than the U.S. dollar, as well as unrealized gains and losses from certain investment activities. Unrealized foreign currency activity for both the three month periods ended March 31, 2018 and 2017 is primarily related to translation gains and losses resulting from the Company’s Canadian operations, and investment activity for both the three month periods ended March 31, 2018 and 2017 relates to unrealized gains and losses on interest rate swaps associated with the Waha JVs.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Note 12 - Income Taxes In determining the quarterly provision for income taxes, management uses an estimated annual effective tax rate based on forecasted annual pre-tax income, permanent tax differences, statutory tax rates and tax planning opportunities in the various jurisdictions in which the Company operates. The effect of significant discrete items is separately recognized in the quarter(s) in which they occur. In December 2017, the Tax Cuts and Jobs Act of 2017 (the “2017 Tax Act”) was enacted, which included broad tax reform that is applicable to the Company. Under the provisions of the 2017 Tax Act, the U.S. corporate tax rate decreased from 35% to 21% effective January 1, 2018. The Company completed an initial remeasurement of its U.S. deferred tax assets and liabilities as of December 31, 2017 as a result of this new tax law and recognized a non-cash tax benefit of $120.1 million in the fourth quarter of 2017 . This initial remeasurement contained estimates of the effect of the 2017 Tax Act, as permitted under Staff Accounting Bulletin (“SAB”) 118, and may be affected by future guidance. In March 2018, the FASB issued ASU 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118 (“ASU 2018-05”), which amended Topic 740 to incorporate the requirements of SAB 118. Any revisions to the initial remeasurement of the Company’s deferred tax assets and liabilities as of December 31, 2017 for the effects of the 2017 Tax Act will be treated in accordance with the measurement period guidance as outlined in Topic 740 and SAB 118.

Segments and Related Informatio

Segments and Related Information	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segments and Related Information	Note 13 - Segments and Related Information Segment Discussion MasTec manages its operations under five operating segments, which represent MasTec’s five reportable segments: (1) Communications; (2) Oil and Gas; (3) Electrical Transmission; (4) Power Generation and Industrial and (5) Other. This structure is generally focused on broad end-user markets for MasTec’s labor-based construction services. All five reportable segments derive their revenue from the engineering, installation and maintenance of infrastructure, primarily in North America. The Communications segment performs engineering, construction, maintenance and customer fulfillment activities related to communications infrastructure primarily for wireless and wireline/fiber communications and install-to-the-home customers, and, to a lesser extent, infrastructure for utilities, among others. MasTec performs engineering, construction and maintenance services on oil and natural gas pipelines and processing facilities for the energy and utilities industries through its Oil and Gas segment. The Electrical Transmission segment primarily serves the energy and utility industries through the engineering, construction and maintenance of electrical transmission lines and substations. The Power Generation and Industrial segment primarily serves energy, utility and other end-markets through the installation and construction of conventional and renewable power facilities, related electrical transmission infrastructure, ethanol/biofuel facilities and various types of heavy civil and industrial infrastructure. The Other segment includes equity investees, the services of which vary from those provided by the Company’s four primary segments, as well as other small business units that perform construction and other services for a variety of international end-markets. Earnings before interest, taxes, depreciation and amortization (“EBITDA”) is the measure of profitability used by management to manage its segments and, accordingly, in its segment reporting. As appropriate, the Company supplements the reporting of consolidated financial information determined in accordance with U.S. GAAP with certain non-U.S. GAAP financial measures, including EBITDA. The Company believes these non-U.S. GAAP measures provide meaningful information and help investors understand the Company’s financial results and assess its prospects for future performance. The Company uses EBITDA to evaluate its performance, both internally and as compared with its peers, because it excludes certain items that may not be indicative of the Company’s core operating results for its reportable segments, as well as items that can vary widely across different industries or among companies within the same industry, and for non-cash stock-based compensation expense, can also be subject to volatility from changes in the market price per share of the Company’s common stock or variations in the value of shares granted. Segment EBITDA is calculated in a manner consistent with consolidated EBITDA. Summarized financial information for MasTec’s reportable segments is presented and reconciled to consolidated financial information for total MasTec in the following tables, including a reconciliation of consolidated income before income taxes to EBITDA (in millions). The tables below may contain slight summation differences due to rounding. For the Three Months Ended March 31 Revenue: 2018 2017 Communications (a) $ 627.1 $ 559.5 Oil and Gas 536.5 455.9 Electrical Transmission 114.0 98.8 Power Generation and Industrial 117.6 46.6 Other 1.9 1.7 Eliminations (0.3 ) (4.3 ) Consolidated revenue $ 1,396.8 $ 1,158.2 (a) Revenue generated primarily by utilities customers represented 17.8% and 13.4% of Communications segment revenue for the three month periods ended March 31, 2018 and 2017 , respectively. For the Three Months Ended March 31 EBITDA: 2018 2017 Communications $ 82.1 $ 48.4 Oil and Gas 33.0 93.9 Electrical Transmission 4.6 3.2 Power Generation and Industrial 4.8 0.8 Other 5.9 (5.3 ) Corporate (25.8 ) (17.5 ) Consolidated EBITDA $ 104.6 $ 123.5 For the Three Months Ended March 31 Depreciation and Amortization: 2018 2017 Communications $ 14.6 $ 12.0 Oil and Gas 25.5 21.9 Electrical Transmission 5.3 5.8 Power Generation and Industrial 3.0 1.5 Other 0.0 0.0 Corporate 1.5 1.7 Consolidated depreciation and amortization $ 49.9 $ 42.9 For the Three Months Ended March 31 EBITDA Reconciliation: 2018 2017 Income before income taxes $ 37.6 $ 68.0 Plus: Interest expense, net 17.1 12.6 Depreciation and amortization 49.9 42.9 Consolidated EBITDA $ 104.6 $ 123.5 Foreign Operations. MasTec operates in North America, primarily in the United States and Canada, and, to a lesser extent, in Mexico. For the three month periods ended March 31, 2018 and 2017 , revenue of $1.4 billion and $1.1 billion , respectively, was derived from U.S. operations, and revenue of $33.8 million and $59.2 million , respectively, was derived from foreign operations, the majority of which was from the Company’s Canadian operations in the Oil and Gas segment. Long-lived assets held in the U.S. included property and equipment, net, of $658.1 million and $649.5 million as of March 31, 2018 and December 31, 2017 , respectively, and, for the Company’s businesses in foreign countries, the majority of which are in Canada, totaled $51.7 million and $57.0 million , respectively. Intangible assets and goodwill, net, related to the Company’s U.S. operations totaled approximately $1.2 billion as of both March 31, 2018 and December 31, 2017 , and for the Company’s businesses in foreign countries, the majority of which are in Canada, totaled approximately $109.5 million and $112.8 million as of March 31, 2018 and December 31, 2017 , respectively. Amounts due from customers from which foreign revenue was derived accounted for approximately 5% of the Company’s consolidated net accounts receivable position, which represents accounts receivable, net, less BIEC, as of both March 31, 2018 and December 31, 2017 . Significant Customers Revenue concentration information for significant customers as a percentage of total consolidated revenue was as follows: For the Three Months Ended March 31 Customer: 2018 2017 AT&T (including DIRECTV ® ) (a) 27% 36% Energy Transfer affiliates (b) 26% 17% (a) The Company’s relationship with AT&T is based upon multiple separate master service and other service agreements, including for installation and maintenance services, as well as construction/installation contracts for AT&T’s: (i) wireless business; (ii) wireline/fiber businesses; and (iii) various install-to-the-home businesses, including DIRECTV®. Revenue from AT&T is included in the Communications segment. (b) The Company's relationship with Energy Transfer affiliates is based upon various construction contracts for pipeline activities with Energy Transfer Partners L.P., and its subsidiaries and affiliates, all of which are consolidated by Energy Transfer Equity, L.P. Revenue from Energy Transfer affiliates is included in the Oil and Gas segment.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
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. See Note 14 - Commitments and Contingencies in the Company’s 2017 Form 10-K for additional information. 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. 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, 2018 and December 31, 2017 , there were $131.7 million and $157.1 million , respectively, of letters of credit issued under the Company’s Credit Facility. The Company is not aware of material claims relating to its outstanding letters of credit as of March 31, 2018 or December 31, 2017 . 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, 2018 and December 31, 2017 , outstanding performance and payment bonds totaled $129.6 million and $119.7 million , respectively, and estimated costs to complete projects secured by these bonds totaled $127.7 million and $46.0 million as of March 31, 2018 and December 31, 2017 , 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 several 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, 2018 , 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, 2018 and December 31, 2017 are amounts held by entities that are proportionately consolidated totaling $18.8 million and $17.3 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 $10.3 million as of March 31, 2018 . The Company has other investment arrangements, as discussed in Note 4 - Fair Value of Financial Instruments and Note 15 - Related Party Transactions. The Company may incur costs or provide financing, performance, financial and/or other guarantees to or in connection with these 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, 2018 and December 31, 2017 , MasTec’s liability for unpaid claims and associated expenses, including incurred but not reported losses related to these policies, totaled $111.8 million and $106.2 million , respectively, of which $76.6 million and $72.2 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 liability for employee group medical claims totaled $2.4 million and $2.6 million as of March 31, 2018 and December 31, 2017 , respectively. The Company is required to post letters of credit and provide cash collateral to certain of its insurance carriers and to provide surety bonds in certain states. Insurance-related letters of credit for the Company’s workers’ compensation, general liability and automobile liability policies amounted to $88.9 million as of both March 31, 2018 and December 31, 2017 . 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, 2018 and December 31, 2017 . Outstanding surety bonds related to workers’ compensation self-insurance programs amounted to $15.2 million as of both March 31, 2018 and December 31, 2017 . 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, 2018 , 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, 2018 and December 31, 2017 , 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. Accrued warranty claims are, and historically have been, de minimis. 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 350 customers for the three month period ended March 31, 2018 . As of March 31, 2018 and December 31, 2017 , one customer accounted for approximately 43% and 46% , respectively, of the Company’s consolidated net accounts receivable position, which represents accounts receivable, net, less BIEC. As of March 31, 2018 and December 31, 2017 , a separate customer accounted for approximately 16% and 15% , respectively, of the Company’s consolidated net accounts receivable position. In addition, the Company derived 74% and 76% , respectively, of its revenue from its top ten customers for the three month periods ended March 31, 2018 and 2017 .

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Note 15 - Related Party Transactions MasTec purchases, rents and leases equipment and purchases various types of supplies and services used in its business from a number of different vendors on a non-exclusive basis, including entities that are associated with members of subsidiary management. For the three month periods ended March 31, 2018 and 2017 , related party lease payments for operational facilities and equipment totaled approximately $7.5 million and $12.7 million , respectively. Payables associated with these related party leases totaled approximately $3.4 million and $0.1 million as of March 31, 2018 and December 31, 2017 , respectively. Additionally, payments to related parties for various types of supplies and services, including ancillary construction services, project-related site restoration and marketing and business development activities totaled approximately $9.0 million and $6.6 million for the three month periods ended March 31, 2018 and 2017 , respectively. As of March 31, 2018 and December 31, 2017 , related amounts payable totaled approximately $1.4 million and $5.2 million , respectively. In the third quarter of 2017, MasTec entered into an arrangement to perform construction services for an entity of which a member of subsidiary management is a minority owner. Revenue from this arrangement totaled approximately $2.7 million for the three month period ended March 31, 2018 , and related amounts receivable totaled approximately $2.0 million and $0.6 million as of March 31, 2018 and December 31, 2017 , respectively. In the third quarter of 2017, MasTec acquired an oil and gas pipeline equipment company that was formerly owned by a member of subsidiary management for approximately $40.6 million in cash and an estimated earn-out liability of $59.9 million as of March 31, 2018 . MasTec previously leased equipment from this company. In February 2018, MasTec acquired a construction management firm specializing in steel building systems, of which Juan Carlos Mas, who is the brother of Jorge Mas, Chairman of MasTec’s Board of Directors, and José R. Mas, MasTec’s Chief Executive Officer, was a minority owner, for approximately $5.4 million in cash and an estimated earn-out liability of approximately $1.3 million as of March 31, 2018 . The net assets acquired included notes payable to the former owners totaling approximately $2.6 million , which amount was subsequently repaid. MasTec rents and leases equipment and purchases equipment supplies used in its business from CCI, in which it has a 15% equity investment. Juan Carlos Mas serves as the chairman of CCI, and a member of management of a MasTec subsidiary is a minority owner. MasTec paid CCI approximately $5.9 million and $1.0 million , net of rebates, for the three month periods ended March 31, 2018 and 2017 , respectively, for equipment supplies, rentals, leases and servicing. Related amounts payable, net of rebates receivable, totaled approximately $3.4 million as of March 31, 2018 , and as of December 31, 2017 , were de minimis. MasTec has a subcontracting arrangement with an entity for the performance of construction services, the minority owners of which include an entity controlled by Jorge Mas and José R. Mas, along with two members of management of a MasTec subsidiary. For the three month periods ended March 31, 2018 and 2017 , MasTec incurred approximately $5.0 million and $0.6 million , respectively, of expenses under this subcontracting arrangement. As of March 31, 2018 and December 31, 2017 , related amounts payable totaled approximately $1.0 million and $2.0 million , respectively. MasTec leases employees to a customer in which Jorge Mas and José R. Mas own a majority interest. For both the three month periods ended March 31, 2018 and 2017 , MasTec charged approximately $0.2 million to this customer. As of both March 31, 2018 and December 31, 2017 , outstanding receivables from employee leasing arrangements with this customer totaled approximately $0.2 million . The Company also provides satellite communication services to this customer. For the three month periods ended March 31, 2018 and 2017 , revenue from satellite communication services provided to this customer totaled approximately $0.3 million and $0.2 million , respectively. As of both March 31, 2018 and December 31, 2017 , amounts receivable from this arrangement totaled approximately $0.3 million . MasTec has a leasing arrangement with an independent third party that leases an aircraft from a Company owned by Jorge Mas. For both the three month periods ended March 31, 2018 and 2017 , MasTec paid approximately $0.5 million under this leasing arrangement. As of both March 31, 2018 and December 31, 2017 , related amounts payable were de minimis. The Company has a 40% interest in an entity that is accounted for as an equity method investment. As of both March 31, 2018 and December 31, 2017 , advances outstanding from this entity, net, totaled approximately $0.3 million . The Company’s Pacer subsidiary has a subcontracting arrangement with a contractual joint venture in which it holds a 35% undivided interest. For the three month periods ended March 31, 2018 and 2017 , revenue recognized by the Company in connection with this arrangement totaled approximately $0.3 million and $0.1 million , respectively. As of March 31, 2018 and December 31, 2017 , accounts receivable, net of BIEC, from this contractual joint venture totaled approximately $0.7 million and $0.8 million , respectively. Outstanding performance guarantees on behalf of this contractual joint venture, which are based on the original full contract value of the associated project, totaled Canadian $132.1 million as of both March 31, 2018 and December 31, 2017 (or approximately $102.4 million and $105.1 million , respectively). Additionally, the Company provided project-related financing in connection with this contractual joint venture of approximately $0.6 million and $0.8 million for the three month periods ended March 31, 2018 and 2017 , respectively. As of March 31, 2018 , there were no additional amounts committed to this entity. Non-controlling interests in entities consolidated by the Company represent ownership interests held by members of management of certain of the Company’s subsidiaries, primarily in the Company’s Oil and Gas segment. In October 2017, the Company acquired the remaining non-controlling interests of one of these entities, with which it had a subcontracting arrangement for the performance of ancillary oil and gas construction services, for approximately $21.4 million in cash and an estimated earn-out liability of $9.0 million as of March 31, 2018 , which liability is reflected within other current and other long-term liabilities, as appropriate. For the three month periods ended March 31, 2018 and 2017 , the Company made distributions of earnings of approximately $0.6 million and $1.3 million , respectively, to holders of these non-controlling interests. Split Dollar Agreements In the first quarter of 2018, Jorge Mas, the Company, and José R. Mas and Juan Carlos Mas, as trustees of the Jorge Mas trust, entered into an amended and restated split dollar life insurance agreement that replaced the prior split dollar agreement with Jorge Mas. Additionally, in the first quarter of 2018, José R. Mas, the Company, and Jorge Mas, Juan Carlos Mas and Patricia Mas, as trustees of the José R. Mas trust, entered into an amended and restated split dollar life insurance agreement that replaced the prior split dollar life insurance agreement with José R. Mas. For details of the amended and restated split dollar life insurance agreements with each of Jorge and José R. Mas, see Note 15 - Related Party Transactions in the Company’s 2017 Form 10-K. No payments were made in connection with either the current or predecessor agreements in either of the three month periods ended March 31, 2018 or 2017 . As of both March 31, 2018 and December 31, 2017 , life insurance assets associated with these agreements, which amounts are included within other long-term assets, totaled approximately $16.6 million .

Supplemental Guarantor Financia

Supplemental Guarantor Financial Information	3 Months Ended
	Mar. 31, 2018
Condensed Unaudited Financial Statements, Supplemental Guarantor Information [Abstract]
Supplemental Guarantor Financial Information	Note 16 – Supplemental Guarantor Condensed Unaudited Consolidating Financial Information The 4.875% Senior Notes are fully and unconditionally guaranteed on an unsecured, unsubordinated, joint and several basis by certain of the Company’s existing and future 100%-owned direct and indirect domestic subsidiaries that are, as of March 31, 2018, each guarantors of the Credit Facility or other outstanding indebtedness (the “Guarantor Subsidiaries”). The Company’s subsidiaries organized outside of the United States and certain domestic subsidiaries (collectively, the “Non-Guarantor Subsidiaries”) do not guarantee these notes. A Guarantor Subsidiary’s guarantee is subject to release in certain customary circumstances, including upon the sale of a majority of the capital stock or substantially all of the assets of such Guarantor Subsidiary; if the Guarantor Subsidiary’s guarantee under the Company’s Credit Facility and other indebtedness is released or discharged (other than due to payment under such guarantee); or when the requirements for legal defeasance are satisfied or the obligations are discharged in accordance with the related indentures. The following supplemental financial information sets forth the condensed unaudited consolidating balance sheets and the condensed unaudited consolidating statements of operations and comprehensive income (loss) and cash flows for MasTec, Inc., the Guarantor Subsidiaries on a combined basis, the Non-Guarantor Subsidiaries on a combined basis and the eliminations necessary to arrive at the information for the Company as reported on a consolidated basis. Eliminations represent adjustments to eliminate investments in subsidiaries and intercompany balances and transactions between or among MasTec, Inc., the Guarantor Subsidiaries and the Non-Guarantor Subsidiaries. Investments in subsidiaries are accounted for using the equity method for this presentation. CONDENSED UNAUDITED CONSOLIDATING STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) (in millions) For the Three Months Ended March 31, 2018 MasTec, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated MasTec, Inc. Revenue $ — $ 1,265.6 $ 185.6 $ (54.4 ) $ 1,396.8 Costs of revenue, excluding depreciation and amortization — 1,136.2 155.5 (54.4 ) 1,237.3 Depreciation and amortization — 43.3 6.6 — 49.9 General and administrative expenses 0.8 59.2 3.6 — 63.6 Interest expense (income), net — 32.9 (15.8 ) — 17.1 Equity in earnings of unconsolidated affiliates — — (5.6 ) — (5.6 ) Other income, net — (2.6 ) (0.5 ) — (3.1 ) (Loss) income before income taxes $ (0.8 ) $ (3.4 ) $ 41.8 $ — $ 37.6 Benefit from (provision for) income taxes 0.2 0.8 (12.1 ) — (11.1 ) Net (loss) income before equity in income from subsidiaries $ (0.6 ) $ (2.6 ) $ 29.7 $ — $ 26.5 Equity in income from subsidiaries, net of tax 27.1 — — (27.1 ) — Net income (loss) $ 26.5 $ (2.6 ) $ 29.7 $ (27.1 ) $ 26.5 Net loss attributable to non-controlling interests — — (0.1 ) — (0.1 ) Net income (loss) attributable to MasTec, Inc. $ 26.5 $ (2.6 ) $ 29.8 $ (27.1 ) $ 26.6 Comprehensive income (loss) $ 33.8 $ (2.6 ) $ 36.8 $ (34.3 ) $ 33.7 For the Three Months Ended March 31, 2017 MasTec, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated MasTec, Inc. Revenue $ — $ 1,083.2 $ 87.9 $ (12.9 ) $ 1,158.2 Costs of revenue, excluding depreciation and amortization — 888.7 95.3 (12.9 ) 971.1 Depreciation and amortization — 35.3 7.6 — 42.9 General and administrative expenses 0.6 59.6 4.6 — 64.8 Interest expense (income), net — 27.9 (15.3 ) — 12.6 Equity in earnings of unconsolidated affiliates — — (1.6 ) — (1.6 ) Other expense, net — — 0.4 — 0.4 (Loss) income before income taxes $ (0.6 ) $ 71.7 $ (3.1 ) $ — $ 68.0 Benefit from (provision for) income taxes 0.2 (26.3 ) (1.3 ) — (27.4 ) Net (loss) income before equity in income from subsidiaries $ (0.4 ) $ 45.4 $ (4.4 ) $ — $ 40.6 Equity in income from subsidiaries, net of tax 41.4 — — (41.4 ) — Net income (loss) $ 41.0 $ 45.4 $ (4.4 ) $ (41.4 ) $ 40.6 Net loss attributable to non-controlling interests — (0.1 ) (0.2 ) — (0.3 ) Net income (loss) attributable to MasTec, Inc. $ 41.0 $ 45.5 $ (4.2 ) $ (41.4 ) $ 41.0 Comprehensive income (loss) $ 42.8 $ 45.5 $ (2.7 ) $ (43.2 ) $ 42.4 CONDENSED UNAUDITED CONSOLIDATING BALANCE SHEETS (in millions) As of March 31, 2018 MasTec, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated MasTec, Inc. Assets Total current assets $ — $ 1,641.5 $ 376.6 $ (110.5 ) $ 1,907.6 Property and equipment, net — 648.2 61.6 — 709.8 Goodwill and other intangible assets, net — 1,195.6 137.3 — 1,332.9 Investments in and advances to consolidated affiliates, net 1,356.0 1,016.6 702.5 (3,075.1 ) — Other long-term assets 15.7 23.8 164.5 — 204.1 Total assets $ 1,371.7 $ 4,525.7 $ 1,442.5 $ (3,185.6 ) $ 4,154.3 Liabilities and equity Total current liabilities $ — $ 996.7 $ 161.1 $ (110.5 ) $ 1,047.3 Long-term debt — 1,336.0 7.5 — 1,343.5 Other long-term liabilities — 380.4 8.9 — 389.3 Total liabilities $ — $ 2,713.1 $ 177.5 $ (110.5 ) $ 2,780.2 Total equity $ 1,371.7 $ 1,812.6 $ 1,265.0 $ (3,075.1 ) $ 1,374.2 Total liabilities and equity $ 1,371.7 $ 4,525.7 $ 1,442.5 $ (3,185.6 ) $ 4,154.3 As of December 31, 2017 MasTec, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated MasTec, Inc. Assets Total current assets $ — $ 1,536.6 $ 332.9 $ (17.1 ) $ 1,852.4 Property and equipment, net — 638.7 67.8 — 706.5 Goodwill and other intangible assets, net — 1,187.9 141.0 — 1,328.9 Investments in and advances to consolidated affiliates, net 1,415.0 847.7 746.6 (3,009.3 ) — Other long-term assets 15.8 23.4 139.6 — 178.8 Total assets $ 1,430.8 $ 4,234.3 $ 1,427.9 $ (3,026.4 ) $ 4,066.6 Liabilities and equity Total current liabilities $ — $ 778.6 $ 202.3 $ (17.1 ) $ 963.8 Long-term debt — 1,269.4 11.3 — 1,280.7 Other long-term liabilities — 379.9 8.8 — 388.7 Total liabilities $ — $ 2,427.9 $ 222.4 $ (17.1 ) $ 2,633.2 Total equity $ 1,430.8 $ 1,806.4 $ 1,205.5 $ (3,009.3 ) $ 1,433.4 Total liabilities and equity $ 1,430.8 $ 4,234.3 $ 1,427.9 $ (3,026.4 ) $ 4,066.6 CONDENSED UNAUDITED CONSOLIDATING STATEMENTS OF CASH FLOWS (in millions) For the Three Months Ended March 31, 2018 MasTec, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated MasTec, Inc. Net cash provided by (used in) operating activities $ — $ 114.0 $ (30.5 ) $ — $ 83.5 Cash flows from investing activities: Cash paid for acquisitions, net of cash acquired — (4.3 ) — — (4.3 ) Capital expenditures — (22.4 ) (0.1 ) — (22.5 ) Proceeds from sale of property and equipment — 4.8 0.6 — 5.4 Payments for other investments — — (14.8 ) — (14.8 ) Proceeds from other investments — — 5.4 — 5.4 Net cash used in investing activities $ — $ (21.9 ) $ (8.9 ) $ — $ (30.9 ) Cash flows from financing activities: Proceeds from credit facilities — 810.6 6.3 — 816.9 Repayments of credit facilities — (736.6 ) (10.5 ) — (747.1 ) Repayments of other borrowings and capital lease obligations — (30.6 ) (2.1 ) — (32.7 ) Repurchase of common stock (90.9 ) — — — (90.9 ) Distributions to non-controlling interests — (0.6 ) — — (0.6 ) Proceeds from stock-based awards, net 0.9 — — — 0.9 Net financing activities and advances from (to) consolidated affiliates 90.0 (132.3 ) 42.3 — — Net cash (used in) provided by financing activities $ — $ (89.5 ) $ 36.0 $ — $ (53.5 ) Effect of currency translation on cash — — 0.7 — 0.7 Net increase (decrease) in cash and cash equivalents $ — $ 2.6 $ (2.7 ) $ — $ (0.1 ) Cash and cash equivalents - beginning of period $ — $ 10.0 $ 30.3 $ — $ 40.3 Cash and cash equivalents - end of period $ — $ 12.6 $ 27.6 $ — $ 40.2 For the Three Months Ended March 31, 2017 MasTec, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated MasTec, Inc. Net cash provided by (used in) operating activities $ — $ 179.5 $ (25.3 ) $ — $ 154.2 Cash flows from investing activities: Cash paid for acquisitions, net of cash acquired — — — — — Capital expenditures — (27.8 ) (1.1 ) — (28.9 ) Proceeds from sale of property and equipment — 0.4 0.1 — 0.5 Payments for other investments — — (53.3 ) — (53.3 ) Proceeds from other investments — — 12.1 — 12.1 Net cash used in investing activities $ — $ (27.4 ) $ (42.2 ) $ — $ (69.6 ) Cash flows from financing activities: Proceeds from credit facilities — 357.2 4.5 — 361.7 Repayments of credit facilities — (439.0 ) (8.1 ) — (447.1 ) Repayments of other borrowings and capital lease obligations — (12.0 ) (2.3 ) — (14.4 ) Distributions to non-controlling interests — (1.3 ) — — (1.3 ) Payments for stock-based awards, net (0.8 ) — — — (0.8 ) Other financing activities, net — (6.0 ) — — (6.0 ) Net financing activities and advances from (to) consolidated affiliates 0.8 (78.8 ) 78.0 — — Net cash (used in) provided by financing activities $ — $ (179.9 ) $ 72.1 $ — $ (107.8 ) Effect of currency translation on cash — — 0.2 — 0.2 Net (decrease) increase in cash and cash equivalents $ — $ (27.8 ) $ 4.8 $ — $ (23.1 ) Cash and cash equivalents - beginning of period $ — $ 28.9 $ 9.9 $ — $ 38.8 Cash and cash equivalents - end of period $ — $ 1.1 $ 14.7 $ — $ 15.7

Business, Basis of Presentati23

Business, Basis of Presentation and Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
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, 2017 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, 2017 contained in the Company’s 2017 Annual Report on Form 10-K (the “ 2017 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. All significant intercompany balances and transactions have been eliminated in consolidation. Other parties’ interests in entities that MasTec consolidates 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 for 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. Income or loss from these investments is recorded as a separate line item in the statements of operations. Intercompany profits or losses associated with the Company’s equity method investments are eliminated until realized by the investee in transactions with third parties. For equity investees in which the Company has an undivided interest in the assets, liabilities and profits or losses of an unincorporated entity, but the Company does not exercise control over the entity, the Company consolidates its proportional interest in the accounts of the entity. Equity investments, other than those accounted for as equity method investments or those that are consolidated, are measured at fair value if their fair values are readily determinable. Equity investments that do not have readily determinable fair values are measured at cost, adjusted for changes from observable market transactions, less impairment. Realized and unrealized gains or losses related to equity investments are recognized in other income or expense. Management determines whether each business entity in which it has equity interests, debt, or other investments constitutes a variable interest entity (“VIE”) based on the nature and characteristics of such arrangements. If an investment arrangement is determined to be a VIE, then management determines if the Company is the VIE’s primary beneficiary by evaluating several factors, including the Company’s: (i) risks and responsibilities; (ii) ownership interests; (iii) decision making powers; and (iv) financial interests, among other factors. If management determines the Company is the primary beneficiary of a VIE, then it would be consolidated, and other parties’ interests in the VIE would be accounted for as non-controlling interests. 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.
Equity Method Investments	The Company’s investments in entities for 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. Income or loss from these investments is recorded as a separate line item in the statements of operations. Intercompany profits or losses associated with the Company’s equity method investments are eliminated until realized by the investee in transactions with third parties.
Unincorporated Entities, Proportionate Consolidation	For equity investees in which the Company has an undivided interest in the assets, liabilities and profits or losses of an unincorporated entity, but the Company does not exercise control over the entity, the Company consolidates its proportional interest in the accounts of the entity.
Other Equity Investments With Readily Determinable Fair Values	Equity investments, other than those accounted for as equity method investments or those that are consolidated, are measured at fair value if their fair values are readily determinable.
Other Equity Investments Without Readily Determinable Fair Values	Equity investments that do not have readily determinable fair values are measured at cost, adjusted for changes from observable market transactions, less impairment. Realized and unrealized gains or losses related to equity investments are recognized in other income or expense.
Variable Interest Entities	Management determines whether each business entity in which it has equity interests, debt, or other investments constitutes a variable interest entity (“VIE”) based on the nature and characteristics of such arrangements. If an investment arrangement is determined to be a VIE, then management determines if the Company is the VIE’s primary beneficiary by evaluating several factors, including the Company’s: (i) risks and responsibilities; (ii) ownership interests; (iii) decision making powers; and (iv) financial interests, among other factors. If management determines the Company is the primary beneficiary of a VIE, then it would be consolidated, and other parties’ interests in the VIE would be accounted for as non-controlling interests. 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. As of March 31, 2018 , the Company determined that certain of its investment arrangements were VIEs; however, because it does not have the power to direct the primary activities that most significantly impact the economic performance of these VIEs, the Company is not the primary beneficiary, and accordingly, has not consolidated these VIEs.
Translation of Foreign Currencies	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 their local currency as their functional currency. Currency gains or losses resulting from transactions executed in currencies other than the functional currency are included in other income or expense, net.
Management Estimates	Management Estimates The preparation of consolidated financial statements in accordance with U.S. GAAP requires the use of estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. These estimates are based on historical experience and various other assumptions, the results of which form the basis of making judgments about the Company’s operating results and the carrying values of assets and liabilities that are not readily apparent from other sources. 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 project-related depreciation, in particular, on construction contracts accounted for under the cost-to-cost method, for which the recorded amounts require estimates of costs to complete and the amount of variable consideration included in the contract transaction price; allowances for doubtful accounts; fair value estimates, including those related to business acquisitions, valuations of goodwill and intangible assets, acquisition-related contingent consideration and equity investments; asset lives used in computing depreciation and amortization; fair values of financial instruments; self-insurance liabilities; other accruals and allowances; income taxes; and the estimated effects of litigation and other contingencies. While management believes that such estimates are reasonable when considered in conjunction with the Company’s consolidated financial position and results of operations taken as a whole, actual results could differ materially from those estimates.
Revenue Recognition	Revenue Recognition The Company adopted the requirements of Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers , which is also referred to as Accounting Standards Codification (“ASC”) Topic 606 (“Topic 606”), under the modified retrospective transition approach effective January 1, 2018, with application to all existing contracts that were not substantially completed as of January 1, 2018. The difference between the recognition criteria under Topic 606 and the Company’s previous revenue recognition practices under the previous revenue recognition guidance, ASC Topic 605-35, was recognized through a cumulative effect adjustment of approximately $2 million that was made to the opening balance of retained earnings as of January 1, 2018. Consistent with the modified retrospective transition approach, the comparative 2017 prior period was not adjusted to conform to the current period presentation. Under Topic 606, revenue is recognized when control of promised goods and services is transferred to customers, and the amount of revenue recognized reflects the consideration to which an entity expects to be entitled in exchange for the goods and services transferred. The adoption of Topic 606 did not have, and is not expected to have, a material effect on the timing or amount of revenue recognized as compared with the Company’s previous revenue recognition practices. Revenue is recognized by the Company primarily over time utilizing the cost-to-cost measure of progress for fixed price contracts and certain master service and other service agreements, consistent with the Company’s previous revenue recognition practices. Under Topic 606, the cost-to-cost measure of progress best depicts the transfer of control of goods or services to the customer for these contracts. Contracts. The Company derives revenue primarily from construction projects performed: i) under master and other service agreements, which provide a menu of available services in a specific geographic territory that are utilized on an as-needed basis, and are typically priced using time and materials or a fixed price per unit basis; or ii) under contracts for specific projects requiring the construction and installation of an entire infrastructure system or specified units within an infrastructure system, which are subject to multiple pricing options, including fixed price, unit price, time and materials, or cost plus a markup. Revenue derived from master service and other service agreements totaled 41% and 46% of consolidated revenue for the three month periods ended March 31, 2018 and 2017 , respectively. Revenue from fixed price contracts provides for a fixed amount of revenue for the entire project. Revenue from these contracts, as well as for certain projects pursuant to master and other service agreements, is recognized over time using the cost-to-cost measure of progress. For these contracts, the cost-to-cost measure of progress best depicts the continuous transfer of control of goods or services to the customer. Such contracts provide that the customer accept completion of progress to date and compensate the Company for services rendered. For certain of the Company’s master service and other service agreements, under which it performs installation and maintenance services, primarily for install-to-the-home service providers in its Communications segment, revenue is recognized at a point in time. This is generally when the work order has been fulfilled and control has been transferred to the customer, which is typically the same day the work order is initiated. Substantially all of the Company’s other revenue is recognized over time. Contract costs include all direct materials, labor and subcontracted costs, as well as indirect costs related to contract performance, such as indirect labor, supplies, tools, repairs and the operational costs of capital equipment. The cost estimation process for recognizing revenue over time under the cost-to-cost method is based on the professional knowledge and experience of the Company’s project managers, engineers and financial professionals. Management reviews estimates of total contract transaction price and total project costs on an ongoing basis. Changes in job performance, job conditions and management’s assessment of expected variable consideration are factors that influence estimates of the total contract transaction price, total costs to complete those contracts and profit recognition. Changes in these factors could result in revisions to revenue and costs of revenue in the period in which the revisions are determined on a prospective basis, which could materially affect the Company’s consolidated results of operations for that period. Provisions for losses on uncompleted contracts are recorded in the period in which such losses are determined. Revenue recognized for the three month period ended March 31, 2018 from performance obligations satisfied, or work completed, in previous periods totaled approximately $44.3 million . Under the typical payment terms of master and other service agreements and fixed price contracts, the customer makes progress payments based on quantifiable measures of performance by the Company as defined by each specific agreement. Progress payments, generally net of amounts retained, are paid by the customer over the duration of the contract. For install-to-the-home contracts, work orders are billed and paid as completed. Amounts billed and due from customers, as well as the amount of contract assets, are classified within accounts receivable, net, in the consolidated balance sheets. See Note 5 - Accounts Receivable, Net, and Contract Assets and Liabilities for related discussion. Amounts expected to be collected beyond one year are classified as other long-term assets. Performance Obligations. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer, and is the unit of account under Topic 606. The transaction price of a contract is allocated to each distinct performance obligation and recognized as revenue when or as the performance obligation is satisfied. The Company’s contracts often require significant integration services, and even when delivering multiple distinct services, are generally accounted for as a single performance obligation. Contract amendments and change orders are generally not distinct from the existing contract due to the significant integration service provided in the context of the contract, and are accounted for as a modification of the existing contract and performance obligation. The majority of the Company’s performance obligations are completed within one year. When more than one contract is entered into with a customer on or close to the same date, the Company evaluates whether those contracts should be combined and accounted for as a single contract as well as whether those contracts should be accounted for as more than one performance obligation. This evaluation requires significant judgment and is based on the facts and circumstances of the various contracts, which could change the amount of revenue and profit recognition in a given period depending upon the outcome of the evaluation. Remaining performance obligations represent the amount of unearned transaction prices for fixed price contracts and open purchase orders or work orders under master and other service agreements for which work is wholly or partially unperformed. As of March 31, 2018 , the amount of the Company’s remaining performance obligations was $5.4 billion . The Company expects to recognize approximately $3.9 billion of its remaining performance obligations as revenue in 2018, with the remainder recognized primarily in 2019. Variable Consideration. Transaction pricing for the Company’s contracts may include variable consideration, which is comprised of items such as change orders, claims, incentives and liquidated damages. Management estimates variable consideration for a performance obligation utilizing estimation methods that best predict the amount of consideration to which the Company will be entitled. Variable consideration is included in the estimated transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. Management’s estimates of variable consideration and determination of whether to include estimated amounts in transaction price are based largely on engineering studies and legal opinions, past practices with the customer, specific discussions, correspondence or preliminary negotiations with the customer and all other relevant information that is reasonably available. The effect of variable consideration on the transaction price of a performance obligation is typically recognized as an adjustment to revenue on a cumulative catch-up basis. To the extent unapproved change orders, claims and liquidated damages reflected in transaction price are not resolved in the Company’s favor, or to the extent incentives reflected in transaction price are not earned, there could be reductions in, or reversals of, previously recognized revenue. As of March 31, 2018 and December 31, 2017 , the Company included approximately $280 million and $146 million , respectively, of change orders and/or claims in the transaction price for certain contracts that were in the process of being resolved in the normal course of business, including through negotiation, arbitration and other proceedings. These transaction price adjustments are included within costs and earnings in excess of billings or accounts receivable, net, as appropriate. As of March 31, 2018 and December 31, 2017 , these change orders and/or claims were primarily related to certain large long-haul pipeline construction projects in the Oil and Gas segment that are expected to reach substantial completion in the coming months. The Company actively engages with its customers to complete the final approval process, and generally expects these processes to be completed within one year. Amounts ultimately realized upon final acceptance by customers could be higher or lower than such estimated amounts.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements See the revenue recognition discussion within Significant Accounting Policies above, and the recent accounting pronouncements discussion below, for information pertaining to the effects of recently adopted and other recent accounting pronouncements, as updated from the discussion in the Company’s 2017 Form 10-K. Accounting Pronouncements Adopted in 2018 In August 2016, the Financial Accounting Standards Board (“FASB”) issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”) to reduce diversity in practice by providing guidance on the classification of certain cash receipts and payments in the statement of cash flows . This ASU, which the Company adopted as of January 1, 2018, is effective on a retrospective basis, and will result in the reclassification of certain types of activity in the consolidated statement of cash flows, including the reclassification of $12 million of second quarter 2017 acquisition-related contingent consideration payments in excess of acquisition date liabilities from financing to operating cash flows. Additionally, in connection with the adoption of this ASU, the Company elected to account for distributions received from equity method investees using the nature of distributions approach, under which distributions are classified based on the nature of the activity that generated them. The other provisions of this ASU did not have a material effect on the Company’s consolidated financial statements. In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2016-01”), which was further amended in February and in March 2018 by ASU 2018-03, Technical Corrections and Improvements to Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2018-03”) and ASU 2018-04, Investments - Debt Securities (Topic 320) and Regulated Operations (Topic 980): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 117 and SEC Release No. 33-9273 (“ASU 2018-04”) to clarify certain aspects of ASU 2016-01 and to update Securities and Exchange Commission (“SEC”) interpretive guidance in connection with the provisions of ASU 2016-01. These ASUs provide guidance for the recognition, measurement, presentation and disclosure of financial assets and financial liabilities, including equity investments other than those accounted for under the equity method of accounting or those that are consolidated . Equity investments within the scope of these ASUs are required to be measured at fair value with changes in fair value recognized in net income. Equity investments that do not have readily determinable fair values are permitted to be measured at cost, less any impairment, plus or minus any changes resulting from observable price changes for identical or similar investments of the same issuer (the “measurement alternative”). The Company adopted these ASUs as of January 1, 2018, which was applicable to the Company on a prospective basis for its equity investments as they do not have readily determinable fair values, and for which the Company elected to utilize the measurement alternative. The adoption of these ASUs will result in volatility in other income (expense), net, upon the occurrence of any observable price changes or impairments related to its equity investments. For further information pertaining to the Company’s equity investments, see Note 4 - Fair Value of Financial Instruments. The other provisions of these ASUs did not have a material effect on the Company’s consolidated financial statements. Other Recent Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016-02”). ASU 2016-02 provides revised guidance for lease accounting and related disclosure requirements, including a requirement for lessees to recognize right-of use assets and lease liabilities on the balance sheet for leases with durations greater than twelve months. ASU 2016-02 is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted. Modified retrospective application is required for all leases existing as of, or entered into after, the beginning of the earliest comparative period presented in the consolidated financial statements, with certain practical expedients available. The Company will adopt ASU 2016-02 as of January 1, 2019, and expects to utilize the expedients permitted under ASU 2016-02, which allow entities to retain the classification of lease contracts existing as of the date of adoption. The Company is continuing to assess the potential effects of this ASU, which have not yet been quantified, on its consolidated financial statements, business processes, systems and controls. The Company’s assessment, which it expects to substantially complete in the fourth quarter of 2018, includes a detailed review of representative lease contracts at each of the Company’s business units and a comparison of its historical accounting policies and practices to the new standard. Based on the Company’s progress in reviewing its leasing arrangements across all of its business units, the Company expects to recognize incremental lease assets and liabilities on its consolidated balance sheets upon adoption of the standard. This ASU is not expected to have a material effect on the amount of expense recognized in connection with the Company’s current leasing arrangements as compared to current practice, however, based on the Company’s preliminary review of its lease contracts to date, it anticipates that the amount of incremental lease assets and lease liabilities to be recognized upon adoption of this ASU will be material. The Company’s expectations may change as its assessment progresses. For information about the Company’s future lease commitments as of December 31, 2017, see Note 8 - Lease Obligations, in the Company’s 2017 Form 10-K.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share Information	The following table provides details underlying the Company’s earnings per share calculations for the periods indicated (in thousands): For the Three Months Ended March 31 2018 2017 Net income attributable to MasTec: Net income - basic and diluted (a) $ 26,560 $ 40,970 Weighted average shares outstanding: Weighted average shares outstanding - basic 81,150 80,697 Dilutive common stock equivalents 1,071 1,460 Weighted average shares outstanding - diluted 82,221 82,157 Additional information: Weighted average anti-dilutive common stock equivalents (b) — 19 (a) Calculated as total net income less amounts attributable to non-controlling interests. (b) Represents anti-dilutive common stock equivalents as calculated under the treasury stock method.

Goodwill and Other Intangible25

Goodwill and Other Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill by Segment	The following table provides balances for goodwill by reportable segment as of March 31, 2018 (in millions): Communications Oil and Gas Electrical Transmission Power Generation and Industrial Total Goodwill Goodwill, gross $ 466.2 $ 460.4 $ 149.9 $ 141.8 $ 1,218.3 Accumulated impairment loss — (72.9 ) — — (72.9 ) Goodwill, net $ 466.2 $ 387.5 $ 149.9 $ 141.8 $ 1,145.4
Rollforward of Other Intangible Assets	The following table provides a reconciliation of changes in other intangible assets, net, for the period indicated (in millions): Other Intangible Assets Non-Amortizing Amortizing Trade Names Pre-Qualifications Customer Relationships and Backlog Other (a) Total Other intangible assets, gross, as of December 31, 2017 $ 34.5 $ 77.6 $ 223.0 $ 21.8 $ 356.9 Accumulated amortization (152.4 ) (13.4 ) (165.8 ) Other intangible assets, net, as of December 31, 2017 $ 34.5 $ 77.6 $ 70.6 $ 8.4 $ 191.1 Additions from new business combinations — — 2.9 0.3 3.2 Measurement period adjustments (b) — — — (0.7 ) (0.7 ) Amortization expense (4.5 ) (0.4 ) (4.9 ) Currency translation adjustments — (1.2 ) (0.1 ) — (1.3 ) Other intangible assets, net, as of March 31, 2018 $ 34.5 $ 76.4 $ 68.9 $ 7.6 $ 187.4 (a) Consists principally of trade names and non-compete agreements. (b) Represents adjustments to preliminary estimates of the fair values of intangible assets acquired within the measurement period for the Company’s 2017 acquisitions.
Schedule of Consideration Paid and Net Assets Acquired, Business Combinations	The following table summarizes the estimated fair values of consideration paid and net assets acquired as of the respective dates of acquisition, as adjusted (in millions): Acquisition consideration: 2017 Cash $ 120.3 Fair value of contingent consideration (earn-out liability) 96.3 Total consideration transferred $ 216.6 Identifiable assets acquired and liabilities assumed: Current assets, primarily composed of accounts receivable and $2.8 million of cash acquired $ 43.8 Property and equipment and other long-term assets 57.2 Amortizing intangible assets 28.1 Current liabilities, including current portion of capital lease obligations and long-term debt (29.4 ) Long-term debt, including capital lease obligations (9.9 ) Deferred income taxes and other long-term liabilities (10.6 ) Total identifiable net assets $ 79.2 Goodwill $ 137.4 Total net assets acquired, including goodwill $ 216.6

Accounts Receivable, Net and 26

Accounts Receivable, Net and Contract Assets and Liabilities (Tables)	3 Months Ended
	Mar. 31, 2018
Accounts Receivable [Member]
Schedule of Accounts Receivable, Net and Contract Assets and Liabilities [Line Items]
Schedule of Accounts Receivable, Net and Contract Assets and Liabilities	The following table provides details of accounts receivable, net of allowance, contract assets (together, “accounts receivable, net”) and contract liabilities as of the dates indicated (in millions): March 31, December 31, Contract billings $ 679.4 $ 683.9 Less allowance for doubtful accounts (9.0 ) (8.2 ) Accounts receivable, net of allowance $ 670.4 $ 675.7 Retainage 301.9 323.1 Costs and earnings in excess of billings 732.8 599.2 Retainage and costs and earnings in excess of billings (together, “contract assets”) $ 1,034.7 $ 922.3 Accounts receivable, net $ 1,705.1 $ 1,598.0 Billings in excess of costs and earnings 215.7 194.5 Accrued project losses 6.7 11.6 Contract liabilities $ 222.4 $ 206.1

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	The following table provides details of property and equipment, net, including property and equipment held under capital leases as of the dates indicated (in millions): March 31, December 31, Land $ 4.6 $ 4.6 Buildings and leasehold improvements 26.6 26.7 Machinery and equipment 1,285.8 1,261.9 Office furniture and equipment 156.9 149.9 Construction in progress 15.1 12.5 Total property and equipment $ 1,489.0 $ 1,455.6 Less accumulated depreciation and amortization (779.2 ) (749.1 ) Property and equipment, net $ 709.8 $ 706.5

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Schedule of Carrying Values of Debt	The following table provides details of the carrying values of debt as of the dates indicated (in millions): Description Maturity Date March 31, December 31, Senior secured credit facility: February 22, 2022 Revolving loans $ 453.8 $ 377.7 Term loan 391.9 396.9 4.875% Senior Notes March 15, 2023 400.0 400.0 Capital lease obligations, weighted average interest rate of 3.7% In installments through September 1, 2022 187.5 181.2 Other debt obligations Varies 9.2 25.8 Total long-term debt obligations $ 1,442.4 $ 1,381.6 Less unamortized deferred financing costs (12.3 ) (13.0 ) Total debt, net of deferred financing costs $ 1,430.1 $ 1,368.6 Current portion of long-term debt 86.6 87.9 Long-term debt $ 1,343.5 $ 1,280.7

Stock-Based Compensation and 29

Stock-Based Compensation and Other Employee Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2018
Share-based Compensation [Abstract]
Schedule of Activity, Restricted Shares	Activity, restricted shares: (a) Restricted Per Share Weighted Average Grant Date Fair Value Non-vested restricted shares, as of December 31, 2017 1,448,591 $ 23.29 Granted 111,367 50.83 Vested (2,372 ) 50.60 Canceled/forfeited (6,552 ) 22.23 Non-vested restricted shares, as of March 31, 2018 1,551,034 $ 25.23 (a) Includes 27,550 restricted stock units as of both March 31, 2018 and December 31, 2017 , respectively.
Schedule of Activity, Employee Stock Purchase Plans	The following table provides details pertaining to the Company’s ESPPs for the periods indicated: For the Three Months Ended March 31 2018 2017 Cash proceeds (in millions) $ 1.0 $ 0.8 Common shares issued 25,638 24,026 Weighted average price per share $ 39.99 $ 32.51 Weighted average per share grant date fair value $ 9.79 $ 8.49
Schedule of Non-Cash Stock-Based Compensation Expense and Related Tax Effects	Details of non-cash stock-based compensation expense and related tax effects for the periods indicated were as follows (in millions): For the Three Months Ended March 31 2018 2017 Non-cash stock-based compensation expense $ 3.2 $ 3.8 Income Tax Effects: Income tax effect of non-cash stock-based compensation $ 0.8 $ 1.2 Excess tax benefit from non-cash stock-based compensation (a) $ — $ — (a) Excess tax benefits represent cash flows from tax deductions in excess of the tax effect of compensation expense associated with share-based payment arrangements. For the three month period ended March 31, 2018 , tax benefit s, net of tax deficiencies , related to the vesting of share-based payment awards were de minimis, and, for the three month period ended March 31, 2017 , the Company recognized a tax deficiency , net of tax benefits , of $0.2 million .

Other Retirement Plans (Tables)

Other Retirement Plans (Tables)	3 Months Ended
	Mar. 31, 2018
Multiemployer Plans [Abstract]
Schedule of Covered Employees and Contributions, Multiemployer Plans	Total contributions to multiemployer plans and the related number of employees covered by these plans, including with respect to the Company’s Canadian operations, for the periods indicated were as follows: Multiemployer Plans Covered Employees Contributions (in millions) Low High Pension Other Multiemployer Total For the Three Months Ended March 31: 2018 2,018 2,612 $ 11.4 $ 2.0 $ 13.4 2017 550 3,669 $ 3.7 $ 2.6 $ 6.3

Segments and Related Informat31

Segments and Related Information (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Schedule of Financial Information by Reportable Segment	For the Three Months Ended March 31 Revenue: 2018 2017 Communications (a) $ 627.1 $ 559.5 Oil and Gas 536.5 455.9 Electrical Transmission 114.0 98.8 Power Generation and Industrial 117.6 46.6 Other 1.9 1.7 Eliminations (0.3 ) (4.3 ) Consolidated revenue $ 1,396.8 $ 1,158.2 (a) Revenue generated primarily by utilities customers represented 17.8% and 13.4% of Communications segment revenue for the three month periods ended March 31, 2018 and 2017 , respectively. For the Three Months Ended March 31 EBITDA: 2018 2017 Communications $ 82.1 $ 48.4 Oil and Gas 33.0 93.9 Electrical Transmission 4.6 3.2 Power Generation and Industrial 4.8 0.8 Other 5.9 (5.3 ) Corporate (25.8 ) (17.5 ) Consolidated EBITDA $ 104.6 $ 123.5 For the Three Months Ended March 31 Depreciation and Amortization: 2018 2017 Communications $ 14.6 $ 12.0 Oil and Gas 25.5 21.9 Electrical Transmission 5.3 5.8 Power Generation and Industrial 3.0 1.5 Other 0.0 0.0 Corporate 1.5 1.7 Consolidated depreciation and amortization $ 49.9 $ 42.9
Reconciliation of Consolidated Income before Income Taxes to EBITDA	For the Three Months Ended March 31 EBITDA Reconciliation: 2018 2017 Income before income taxes $ 37.6 $ 68.0 Plus: Interest expense, net 17.1 12.6 Depreciation and amortization 49.9 42.9 Consolidated EBITDA $ 104.6 $ 123.5
Schedule of Significant Customers, Revenue Concentration Information	Revenue concentration information for significant customers as a percentage of total consolidated revenue was as follows: For the Three Months Ended March 31 Customer: 2018 2017 AT&T (including DIRECTV ® ) (a) 27% 36% Energy Transfer affiliates (b) 26% 17% (a) The Company’s relationship with AT&T is based upon multiple separate master service and other service agreements, including for installation and maintenance services, as well as construction/installation contracts for AT&T’s: (i) wireless business; (ii) wireline/fiber businesses; and (iii) various install-to-the-home businesses, including DIRECTV®. Revenue from AT&T is included in the Communications segment. (b) The Company's relationship with Energy Transfer affiliates is based upon various construction contracts for pipeline activities with Energy Transfer Partners L.P., and its subsidiaries and affiliates, all of which are consolidated by Energy Transfer Equity, L.P. Revenue from Energy Transfer affiliates is included in the Oil and Gas segment.

Supplemental Guarantor Financ32

Supplemental Guarantor Financial Information (Tables)	3 Months Ended
	Mar. 31, 2018
Condensed Unaudited Financial Statements, Supplemental Guarantor Information [Abstract]
Condensed Unaudited Consolidating Statements of Operations and Comprehensive Income (Loss)	CONDENSED UNAUDITED CONSOLIDATING STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) (in millions) For the Three Months Ended March 31, 2018 MasTec, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated MasTec, Inc. Revenue $ — $ 1,265.6 $ 185.6 $ (54.4 ) $ 1,396.8 Costs of revenue, excluding depreciation and amortization — 1,136.2 155.5 (54.4 ) 1,237.3 Depreciation and amortization — 43.3 6.6 — 49.9 General and administrative expenses 0.8 59.2 3.6 — 63.6 Interest expense (income), net — 32.9 (15.8 ) — 17.1 Equity in earnings of unconsolidated affiliates — — (5.6 ) — (5.6 ) Other income, net — (2.6 ) (0.5 ) — (3.1 ) (Loss) income before income taxes $ (0.8 ) $ (3.4 ) $ 41.8 $ — $ 37.6 Benefit from (provision for) income taxes 0.2 0.8 (12.1 ) — (11.1 ) Net (loss) income before equity in income from subsidiaries $ (0.6 ) $ (2.6 ) $ 29.7 $ — $ 26.5 Equity in income from subsidiaries, net of tax 27.1 — — (27.1 ) — Net income (loss) $ 26.5 $ (2.6 ) $ 29.7 $ (27.1 ) $ 26.5 Net loss attributable to non-controlling interests — — (0.1 ) — (0.1 ) Net income (loss) attributable to MasTec, Inc. $ 26.5 $ (2.6 ) $ 29.8 $ (27.1 ) $ 26.6 Comprehensive income (loss) $ 33.8 $ (2.6 ) $ 36.8 $ (34.3 ) $ 33.7 For the Three Months Ended March 31, 2017 MasTec, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated MasTec, Inc. Revenue $ — $ 1,083.2 $ 87.9 $ (12.9 ) $ 1,158.2 Costs of revenue, excluding depreciation and amortization — 888.7 95.3 (12.9 ) 971.1 Depreciation and amortization — 35.3 7.6 — 42.9 General and administrative expenses 0.6 59.6 4.6 — 64.8 Interest expense (income), net — 27.9 (15.3 ) — 12.6 Equity in earnings of unconsolidated affiliates — — (1.6 ) — (1.6 ) Other expense, net — — 0.4 — 0.4 (Loss) income before income taxes $ (0.6 ) $ 71.7 $ (3.1 ) $ — $ 68.0 Benefit from (provision for) income taxes 0.2 (26.3 ) (1.3 ) — (27.4 ) Net (loss) income before equity in income from subsidiaries $ (0.4 ) $ 45.4 $ (4.4 ) $ — $ 40.6 Equity in income from subsidiaries, net of tax 41.4 — — (41.4 ) — Net income (loss) $ 41.0 $ 45.4 $ (4.4 ) $ (41.4 ) $ 40.6 Net loss attributable to non-controlling interests — (0.1 ) (0.2 ) — (0.3 ) Net income (loss) attributable to MasTec, Inc. $ 41.0 $ 45.5 $ (4.2 ) $ (41.4 ) $ 41.0 Comprehensive income (loss) $ 42.8 $ 45.5 $ (2.7 ) $ (43.2 ) $ 42.4
Condensed Unaudited Consolidating Balance Sheets	CONDENSED UNAUDITED CONSOLIDATING BALANCE SHEETS (in millions) As of March 31, 2018 MasTec, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated MasTec, Inc. Assets Total current assets $ — $ 1,641.5 $ 376.6 $ (110.5 ) $ 1,907.6 Property and equipment, net — 648.2 61.6 — 709.8 Goodwill and other intangible assets, net — 1,195.6 137.3 — 1,332.9 Investments in and advances to consolidated affiliates, net 1,356.0 1,016.6 702.5 (3,075.1 ) — Other long-term assets 15.7 23.8 164.5 — 204.1 Total assets $ 1,371.7 $ 4,525.7 $ 1,442.5 $ (3,185.6 ) $ 4,154.3 Liabilities and equity Total current liabilities $ — $ 996.7 $ 161.1 $ (110.5 ) $ 1,047.3 Long-term debt — 1,336.0 7.5 — 1,343.5 Other long-term liabilities — 380.4 8.9 — 389.3 Total liabilities $ — $ 2,713.1 $ 177.5 $ (110.5 ) $ 2,780.2 Total equity $ 1,371.7 $ 1,812.6 $ 1,265.0 $ (3,075.1 ) $ 1,374.2 Total liabilities and equity $ 1,371.7 $ 4,525.7 $ 1,442.5 $ (3,185.6 ) $ 4,154.3 As of December 31, 2017 MasTec, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated MasTec, Inc. Assets Total current assets $ — $ 1,536.6 $ 332.9 $ (17.1 ) $ 1,852.4 Property and equipment, net — 638.7 67.8 — 706.5 Goodwill and other intangible assets, net — 1,187.9 141.0 — 1,328.9 Investments in and advances to consolidated affiliates, net 1,415.0 847.7 746.6 (3,009.3 ) — Other long-term assets 15.8 23.4 139.6 — 178.8 Total assets $ 1,430.8 $ 4,234.3 $ 1,427.9 $ (3,026.4 ) $ 4,066.6 Liabilities and equity Total current liabilities $ — $ 778.6 $ 202.3 $ (17.1 ) $ 963.8 Long-term debt — 1,269.4 11.3 — 1,280.7 Other long-term liabilities — 379.9 8.8 — 388.7 Total liabilities $ — $ 2,427.9 $ 222.4 $ (17.1 ) $ 2,633.2 Total equity $ 1,430.8 $ 1,806.4 $ 1,205.5 $ (3,009.3 ) $ 1,433.4 Total liabilities and equity $ 1,430.8 $ 4,234.3 $ 1,427.9 $ (3,026.4 ) $ 4,066.6
Condensed Unaudited Consolidating Statements of Cash Flows	CONDENSED UNAUDITED CONSOLIDATING STATEMENTS OF CASH FLOWS (in millions) For the Three Months Ended March 31, 2018 MasTec, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated MasTec, Inc. Net cash provided by (used in) operating activities $ — $ 114.0 $ (30.5 ) $ — $ 83.5 Cash flows from investing activities: Cash paid for acquisitions, net of cash acquired — (4.3 ) — — (4.3 ) Capital expenditures — (22.4 ) (0.1 ) — (22.5 ) Proceeds from sale of property and equipment — 4.8 0.6 — 5.4 Payments for other investments — — (14.8 ) — (14.8 ) Proceeds from other investments — — 5.4 — 5.4 Net cash used in investing activities $ — $ (21.9 ) $ (8.9 ) $ — $ (30.9 ) Cash flows from financing activities: Proceeds from credit facilities — 810.6 6.3 — 816.9 Repayments of credit facilities — (736.6 ) (10.5 ) — (747.1 ) Repayments of other borrowings and capital lease obligations — (30.6 ) (2.1 ) — (32.7 ) Repurchase of common stock (90.9 ) — — — (90.9 ) Distributions to non-controlling interests — (0.6 ) — — (0.6 ) Proceeds from stock-based awards, net 0.9 — — — 0.9 Net financing activities and advances from (to) consolidated affiliates 90.0 (132.3 ) 42.3 — — Net cash (used in) provided by financing activities $ — $ (89.5 ) $ 36.0 $ — $ (53.5 ) Effect of currency translation on cash — — 0.7 — 0.7 Net increase (decrease) in cash and cash equivalents $ — $ 2.6 $ (2.7 ) $ — $ (0.1 ) Cash and cash equivalents - beginning of period $ — $ 10.0 $ 30.3 $ — $ 40.3 Cash and cash equivalents - end of period $ — $ 12.6 $ 27.6 $ — $ 40.2 For the Three Months Ended March 31, 2017 MasTec, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated MasTec, Inc. Net cash provided by (used in) operating activities $ — $ 179.5 $ (25.3 ) $ — $ 154.2 Cash flows from investing activities: Cash paid for acquisitions, net of cash acquired — — — — — Capital expenditures — (27.8 ) (1.1 ) — (28.9 ) Proceeds from sale of property and equipment — 0.4 0.1 — 0.5 Payments for other investments — — (53.3 ) — (53.3 ) Proceeds from other investments — — 12.1 — 12.1 Net cash used in investing activities $ — $ (27.4 ) $ (42.2 ) $ — $ (69.6 ) Cash flows from financing activities: Proceeds from credit facilities — 357.2 4.5 — 361.7 Repayments of credit facilities — (439.0 ) (8.1 ) — (447.1 ) Repayments of other borrowings and capital lease obligations — (12.0 ) (2.3 ) — (14.4 ) Distributions to non-controlling interests — (1.3 ) — — (1.3 ) Payments for stock-based awards, net (0.8 ) — — — (0.8 ) Other financing activities, net — (6.0 ) — — (6.0 ) Net financing activities and advances from (to) consolidated affiliates 0.8 (78.8 ) 78.0 — — Net cash (used in) provided by financing activities $ — $ (179.9 ) $ 72.1 $ — $ (107.8 ) Effect of currency translation on cash — — 0.2 — 0.2 Net (decrease) increase in cash and cash equivalents $ — $ (27.8 ) $ 4.8 $ — $ (23.1 ) Cash and cash equivalents - beginning of period $ — $ 28.9 $ 9.9 $ — $ 38.8 Cash and cash equivalents - end of period $ — $ 1.1 $ 14.7 $ — $ 15.7

Business, Basis of Presentati33

Business, Basis of Presentation and Significant Accounting Policies (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)segment	Jun. 30, 2017USD ($)	Mar. 31, 2017	Jan. 01, 2018USD ($)	Dec. 31, 2017USD ($)
Segment Reporting, Disclosure of Entity's Reportable Segments [Abstract]
Number of reportable segments | segment	5
Revenue [Line Items]
Retained earnings, cumulative effect recognized on intial application of the new guidance	$ 885,277				$ 857,154
Revenue recognition, performance obligations satisfied in previous periods, revenue recognized	44,300
Contract with customer, unapproved change orders and/or claims, amount	$ 280,000				$ 146,000
Maximum [Member]
Revenue [Line Items]
Change order or claim approval process, term within which expected to be completed (in years)	1 year
Maximum [Member] | Plan [Member]
Revenue [Line Items]
Revenue recognition, performance obligations, completion period (in months/years)	1 year
Revenue [Member] | Concentration Risk from Type of Arrangement [Member] | Master Service and Other Service Agreements [Member]
Revenue [Line Items]
Concentration risk, percentage of total	41.00%		46.00%
ASU 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue [Line Items]
Retained earnings, cumulative effect recognized on intial application of the new guidance				$ 2,000
ASU 2016-15 [Member] | Pro Forma [Member]
Revenue [Line Items]
Payments for contingent consideration liabilities, operating activities		$ 12,000

Business, Basis of Presentati34

Business, Basis of Presentation and Significant Accounting Policies (Remaining Performance Obligations) (Narrative) (Details) $ in Billions	3 Months Ended
	Mar. 31, 2018USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue recognition, remaining performance obligations, contract price allocated (in dollars)	$ 3.9
Revenue recognition, remaining performance obligations, completion period (in months/years)	9 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue recognition, remaining performance obligations, contract price allocated (in dollars)	$ 5.4
Revenue recognition, remaining performance obligations, completion period (in months/years)

Earnings Per Share (Narrative)

Earnings Per Share (Narrative) (Details) shares in Millions	3 Months Ended
	Mar. 31, 2018shares
Earnings Per Share [Line Items]
Computation of earnings per share, methodology	Basic earnings or loss per share is computed by dividing net income or loss attributable to MasTec by the weighted average number of common shares outstanding for the period, which excludes non-participating unvested restricted share awards. Diluted earnings per share is computed by dividing net income or loss attributable to MasTec by the weighted average number of fully diluted shares, as calculated under the treasury stock method, which includes the potential effect of dilutive common stock equivalents, such as issued but unvested restricted shares. If the Company reports a loss, rather than income, the computation of diluted loss per share excludes the effect of dilutive common stock equivalents, as their effect would be anti-dilutive.
Treasury Stock, Common [Member] | 2016 Share Repurchase Program [Member]
Earnings Per Share [Line Items]
Treasury stock acquired (in shares)	2

Earnings Per Share (Schedule of

Earnings Per Share (Schedule of Earnings Per Share Information) (Details) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Net income attributable to MasTec:
Net income - basic (in dollars)	[1]	$ 26,560	$ 40,970
Net income - diluted (in dollars)	[1]	$ 26,560	$ 40,970
Weighted average shares outstanding:
Weighted average shares outstanding - basic		81,150	80,697
Dilutive common stock equivalents (in shares)		1,071	1,460
Weighted average shares outstanding - diluted		82,221	82,157
Common Stock [Member]
Additional information:
Weighted average anti-dilutive common stock equivalents (in shares)	[2]	0	19
[1]	Calculated as total net income less amounts attributable to non-controlling interests.
[2]	Represents anti-dilutive common stock equivalents as calculated under the treasury stock method.

Goodwill and Other Intangible37

Goodwill and Other Intangible Assets (Schedule of Goodwill by Segment) (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill, gross	$ 1,218,300,000
Accumulated impairment losses	(72,900,000)
Goodwill, net	1,145,434,000	$ 1,137,738,000
Communications [Member]
Goodwill [Line Items]
Goodwill, gross	466,200,000
Accumulated impairment losses	0
Goodwill, net	466,200,000
Oil and Gas [Member]
Goodwill [Line Items]
Goodwill, gross	460,400,000
Accumulated impairment losses	(72,900,000)
Goodwill, net	387,500,000
Electrical Transmission [Member]
Goodwill [Line Items]
Goodwill, gross	149,900,000
Accumulated impairment losses	0
Goodwill, net	149,900,000
Power Generation and Industrial [Member]
Goodwill [Line Items]
Goodwill, gross	141,800,000
Accumulated impairment losses	0
Goodwill, net	$ 141,800,000

Goodwill and Other Intangible38

Goodwill and Other Intangible Assets (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Goodwill [Line Items]
Goodwill, additions from new business combinations	$ 9.8
Goodwill, measurement period adjustments	(0.6)
Amortization expense, intangible assets	4.9	$ 4.1
Goodwill, Gross [Member]
Goodwill [Line Items]
Goodwill, currency translation gains (losses)	(3.4)	1.1
Goodwill, Accumulated Impairment Losses [Member]
Goodwill [Line Items]
Goodwill, currency translation gains (losses)	$ 1.9	$ (0.6)

Goodwill and Other Intangible39

Goodwill and Other Intangible Assets (Rollforward of Other Intangible Assets) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Other Intangible Assets [Line Items]
Other intangible assets, gross				$ 356,900
Accumulated amortization				(165,800)
Other Intangible Assets [Rollforward]
Other intangible assets, net, beginning balance		$ 191,142
Additions from new business combinations, other intangible assets		3,200
Measurement period adjustments, other intangible assets	[1]	(700)
Amortization expense		(4,900)	$ (4,100)
Currency translation adjustments, other intangible assets		(1,300)
Other intangible assets, net, ending balance		187,442
Customer Relationships and Backlog [Member]
Other Intangible Assets [Line Items]
Other intangible assets, amortizing, gross				223,000
Accumulated amortization				(152,400)
Other Intangible Assets [Rollforward]
Other intangible assets, net, amortizing, beginning balance		70,600
Additions from new business combinations, amortizing intangible assets		2,900
Measurement period adjustments, amortizing intangible assets	[1]	0
Amortization expense		(4,500)
Currency translation adjustments, amortizing intangible assets		(100)
Other intangible assets, net, amortizing, ending balance		68,900
Other Amortizing Intangible Assets [Member]
Other Intangible Assets [Line Items]
Other intangible assets, amortizing, gross	[2]			21,800
Accumulated amortization	[2]			(13,400)
Other Intangible Assets [Rollforward]
Other intangible assets, net, amortizing, beginning balance	[2]	8,400
Additions from new business combinations, amortizing intangible assets	[2]	300
Measurement period adjustments, amortizing intangible assets	[1],[2]	(700)
Amortization expense	[2]	(400)
Currency translation adjustments, amortizing intangible assets	[2]	0
Other intangible assets, net, amortizing, ending balance	[2]	7,600
Trade Names [Member]
Other Intangible Assets [Line Items]
Other intangible assets, non-amortizing, carrying amount		34,500		34,500
Other Intangible Assets [Rollforward]
Other intangible assets, non-amortizing, beginning balance		34,500
Additions from new business combinations, non-amortizing intangible assets		0
Measurement period adjustments, non-amortizing intangible assets	[1]	0
Currency translation adjustments, non-amortizing intangible assets		0
Other intangible assets, non-amortizing, ending balance		34,500
Pre-Qualifications [Member]
Other Intangible Assets [Line Items]
Other intangible assets, non-amortizing, carrying amount		77,600		$ 77,600
Other Intangible Assets [Rollforward]
Other intangible assets, non-amortizing, beginning balance		77,600
Additions from new business combinations, non-amortizing intangible assets		0
Measurement period adjustments, non-amortizing intangible assets	[1]	0
Currency translation adjustments, non-amortizing intangible assets		(1,200)
Other intangible assets, non-amortizing, ending balance		$ 76,400
[1]	Represents adjustments to preliminary estimates of the fair values of intangible assets acquired within the measurement period for the Company’s 2017 acquisitions.
[2]	Consists principally of trade names and non-compete agreements.

Goodwill and Other Intangible40

Goodwill and Other Intangible Assets (2018 Acquisitions) (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earn-Out Liabilities [Member]
Business Combinations [Line Items]
Additions to acquisition-related contingent consideration	$ 4,161	$ 0
2018 Acquisitions [Member]
Business Combinations [Line Items]
Business combinations, percentage of interests acquired	100.00%
Business combinations, cash paid (in dollars)	$ 6,100
2018 Acquisitions [Member] | Earn-Out Liabilities [Member]
Business Combinations [Line Items]
Additions to acquisition-related contingent consideration	$ 1,500
2018 Power Generation and Industrial Acquisition A [Member]
Business Combinations [Line Items]
Business combinations, description of acquired entity	a construction management firm specializing in steel building systems
2018 Power Generation and Industrial Acquisition B [Member]
Business Combinations [Line Items]
Business combinations, description of acquired entity	a wind turbine services company

Goodwill and Other Intangible41

Goodwill and Other Intangible Assets (2017 Acquisitions) (Narrative) (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018USD ($)	Dec. 31, 2017
Earn-Out Liabilities [Member]
Business Combinations [Line Items]
Business combinations, contingent consideration liabilities, range of potential earn-out liabilities, maximum unlimited	there is no maximum payment amount
2017 Acquisitions [Member]
Business Combinations [Line Items]
Business combinations, number of acquisitions		3
Business combinations, percentage of interests acquired	100.00%
Business combinations, acquired finite-lived intangible assets, weighted average useful life (in years)		10 years
Business combinations, goodwill recognized, description	The goodwill balances for the respective acquisitions represent the estimated value of each acquired company’s geographic presence in key markets, its assembled workforce and management team industry-specific project management expertise, as well as synergies expected to be achieved from the combined operations of the acquired companies and MasTec.
Business combinations, goodwill, expected tax deductible amount (in dollars)	$ 90
2017 Acquisitions [Member] | Earn-Out Liabilities [Member]
Business Combinations [Line Items]
Business combinations, contingent consideration, basis for amount	The contingent consideration included in the table above equals the acquired companies’ earnings before interest, taxes, depreciation and amortization (“EBITDA”) above certain thresholds, if applicable, for a period of five years, as set forth in the respective purchase agreements, which amounts are payable annually.
Business combinations, contingent consideration, earn-out period (in years)	5 years
Business combinations, contingent consideration, fair value measurements, valuation techniques	The fair values of the earn-out liabilities were estimated using income approaches such as discounted cash flows or option pricing models and incorporate significant inputs not observable in the market.
Business combinations, contingent consideration, fair value measurements, significant assumptions	Key assumptions in the estimated valuations include the discount rate and probability-weighted EBITDA projections.
Business combinations, contingent consideration liabilities, range of potential undiscounted earn-out liabilities, low (in dollars)	$ 14
Business combinations, contingent consideration liabilities, range of potential undiscounted earn-out liabilities, high (in dollars)	$ 188
Business combinations, contingent consideration liabilities, range of potential earn-out liabilities, maximum unlimited	there is no maximum payment amount
2017 Acquisitions [Member] | Customer Relationships [Member]
Business Combinations [Line Items]
Business combinations, acquired finite-lived intangible assets, weighted average useful life (in years)		11 years
2017 Acquisitions [Member] | Backlog [Member]
Business Combinations [Line Items]
Business combinations, acquired finite-lived intangible assets, weighted average useful life (in years)		4 years
2017 Acquisitions [Member] | Other Amortizing Intangible Assets [Member]
Business Combinations [Line Items]
Business combinations, acquired finite-lived intangible assets, weighted average useful life (in years)		6 years
2017 Communications Acquisition [Member]
Business Combinations [Line Items]
Business combinations, description of acquired entity	a wireline/fiber deployment construction contractor
2017 Power Generation and Industrial Acquisition [Member]
Business Combinations [Line Items]
Business combinations, description of acquired entity	a heavy civil construction services company
2017 Oil and Gas Acquisition [Member]
Business Combinations [Line Items]
Business combinations, description of acquired entity	an oil and gas pipeline equipment company

Goodwill and Other Intangible42

Goodwill and Other Intangible Assets (Schedule of Consideration Paid and Net Assets Acquired, Business Combinations) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Identifiable assets acquired and liabilities assumed:
Goodwill	$ 1,145,434		$ 1,137,738
Earn-Out Liabilities [Member]
Acquisition consideration:
Fair value of contingent consideration (earn-out liability)	$ 4,161	$ 0
2017 Acquisitions [Member]
Acquisition consideration:
Cash			120,300
Total consideration transferred			216,600
Identifiable assets acquired and liabilities assumed:
Current assets, primarily composed of accounts receivable and $2.8 million of cash acquired			43,800
Cash acquired			2,800
Property and equipment and other long-term assets			57,200
Amortizing intangible assets			28,100
Current liabilities, including current portion of capital lease obligations and long-term debt			(29,400)
Long-term debt, including capital lease obligations			(9,900)
Deferred income taxes and other long-term liabilities			(10,600)
Total identifiable net assets			79,200
Goodwill			137,400
Total net assets acquired, including goodwill			216,600
2017 Acquisitions [Member] | Earn-Out Liabilities [Member]
Acquisition consideration:
Fair value of contingent consideration (earn-out liability)			$ 96,300

Goodwill and Other Intangible43

Goodwill and Other Intangible Assets (Unaudited Pro Forma Financial Information) (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Business Combinations, Unaudited Pro Forma Information [Abstract]
Business combinations, unaudited pro forma revenue (in dollars)	$ 1,400.3	$ 1,220.2
Business combinations, unaudited pro forma net income (in dollars)	$ 24.1	$ 42.6
Business combinations, unaudited pro forma information, description	These unaudited pro forma financial results represent the results of operations of the companies acquired as if the acquired companies had been consolidated as of the beginning of the year prior to their acquisition, and are provided for illustrative purposes only. These unaudited pro forma financial results do not purport to be indicative of the actual results that would have been achieved by the combined companies for the periods indicated, or of the results that may be achieved by the combined companies in the future. The Company’s unaudited pro forma financial results were prepared by adjusting the historical results of MasTec to include the historical results of the acquired businesses described above, and then adjusted (i) to remove acquisition costs; (ii) to increase amortization expense resulting from the acquired intangible assets; (iii) to increase interest expense as a result of the cash consideration paid; (iv) to reduce interest expense from debt repaid upon acquisition; and (iv) to eliminate the effects of intercompany transactions. These unaudited pro forma financial results do not include adjustments to reflect other cost savings or synergies that may have resulted from these acquisitions.
Business combinations, acquisition-related results, revenue	$ 76.8
Business combinations, acquisition-related results, net income	$ 2

Fair Value of Financial Instr44

Fair Value of Financial Instruments (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Goodwill, measurement period adjustments	$ (0.6)
Earn-Out Liabilities [Member]
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Goodwill, measurement period adjustments	$ 2.7
Earn-Out Liabilities [Member]
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Acquisition-related contingent consideration liabilities, range of potential earn-out liabilities, maximum unlimited	there is no maximum payment amount
Acquisition-related contingent consideration liabilities, additions	$ 1.5
Earn-Out Liabilities [Member] | Level 3 [Member] | Fair Value Measurements, Recurring [Member]
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Fair value measurements, valuation techniques	The fair value of the Company’s earn-out liabilities is estimated using income approaches such as discounted cash flows or option pricing models and incorporates significant inputs not observable in the market.
Fair value measurements, significant assumptions	Key assumptions include the discount rate and probability-weighted EBITDA projections.
Earn-Out Liabilities [Member] | Level 3 [Member] | Fair Value [Member]
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Acquisition-related contingent consideration liabilities, fair value	$ 121.4	$ 117.2
Earn-Out Liabilities [Member] | Level 3 [Member] | Fair Value [Member] | Fair Value Measurements, Recurring [Member]
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Acquisition-related contingent consideration liabilities, range of potential undiscounted earn-out liabilities, low	28
Acquisition-related contingent consideration liabilities, range of potential undiscounted earn-out liabilities, high	214
Earn-Out Liabilities [Member] | Level 3 [Member] | Fair Value [Member] | Other Current Liabilities [Member]
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Acquisition-related contingent consideration liabilities, fair value	$ 23.8	$ 22.6

Fair Value of Financial Instr45

Fair Value of Financial Instruments (Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis) (Narrative) (Details) - 4.875% Senior Notes [Member] - Senior Notes [Member] - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Debt instrument, interest rate (percentage)	4.875%
Fair Value Measurements, Non-Recurring [Member] | Gross Carrying Amount [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
4.875% Senior Notes (in dollars)	$ 400	$ 400
Fair Value Measurements, Non-Recurring [Member] | Fair Value [Member] | Level 1 [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
4.875% Senior Notes (in dollars)	$ 400	$ 410

Fair Value of Financial Instr46

Fair Value of Financial Instruments (Equity Investments) (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Investment, adjusted cost	$ 18	$ 18
Investee [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Net investment, equity investments	$ 163	141
Waha JVs [Member] | Equity Method Investee [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity investment, ownership percentage	33.00%
Net investment, equity investments	$ 144	$ 121
CCI [Member] | Immediate Family Member of Management [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Investment, adjusted cost	$ 15

Fair Value of Financial Instr47

Fair Value of Financial Instruments (The Waha JVs) (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	$ 5,585,000	$ 1,646,000
Unrealized gains on equity investee activity, net of tax	7,716,000	636,000
Credit Facility [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Letters of credit issued	$ 131,700,000		$ 157,100,000
Waha JVs [Member] | Equity Method Investee [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Number of pipelines in operation	2
Equity investments, equity and other contributions	$ 14,800,000	53,300,000
Equity commitments satisfied, related party (percentage)	100.00%
Equity method investments, cumulative undistributed earnings	$ 16,800,000
Equity investment, distributions of earnings	5,700,000
Net investment, equity investments	144,000,000		121,000,000
Revenue, related parties		151,400,000
Receivables, including retainage, net of BIEC, related parties	200,000		2,800,000
Waha JVs [Member] | Equity Method Investee [Member] | Interest Rate Swap [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Unrealized gains on equity investee activity	10,100,000	1,000,000
Unrealized gains on equity investee activity, net of tax	7,700,000	600,000
Waha JVs [Member] | Equity Method Investee [Member] | Other [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	5,600,000	$ 1,600,000
Waha JVs [Member] | Equity Method Investee [Member] | Credit Facility [Member] | Commercial and/or Financial Standby [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Letters of credit issued	$ 0		$ 19,000,000

Fair Value of Financial Instr48

Fair Value of Financial Instruments (Other Investments - Pensare) (Narrative) (Details) - Pensare [Member] - Chief Executive Officer [Member] - USD ($) $ / shares in Units, $ in Millions	Mar. 31, 2018	Sep. 30, 2017
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity investment and warrants, amount paid (in dollars)		$ 2
Equity investment, ownership percentage	4.00%
Plan [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Warrants, exercise price (in dollars per share)	$ 11.50
Plan [Member] | Common Stock [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Investment, restriction period (in years)	1 year
Warrants [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Derivative instruments, number held	2,000,000

Fair Value of Financial Instr49

Fair Value of Financial Instruments (Other Investments - Pacer) (Narrative) (Details) - Investee [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Net investment, other investments	$ 163		$ 141
Pacer [Member] | Canadian Dollars [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Other equity investee, proceeds related to ongoing liquidation	5.4	$ 12.1
Net investment, other investments	$ 4		$ 9.6

Accounts Receivable, Net and 50

Accounts Receivable, Net and Contract Assets and Liabilities (Schedule of Accounts Receivable, Net and Contract Assets and Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts Receivable, Net and Contract Assets and Liabilities [Abstract]
Contract billings	$ 679,400	$ 683,900
Less allowance for doubtful accounts	(9,000)	(8,200)
Accounts receivable, net of allowance	670,400	675,700
Retainage	301,900	323,100
Costs and earnings in excess of billings	732,800	599,200
Retainage and costs and earnings in excess of billings (together, “contract assets”)	1,034,700	922,300
Accounts receivable, net	1,705,126	1,598,015
Billings in excess of costs and earnings	215,707	194,494
Accrued project losses	6,700	11,600
Contract liabilities	$ 222,400	$ 206,100

Accounts Receivable, Net and 51

Accounts Receivable, Net and Contract Assets and Liabilities (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Schedule of Accounts Receivable, Net and Contract Assets and Liabilities [Line Items]
Revenue recognition, BIEC, revenue recognized	$ 84.8
Provisions for doubtful accounts	0.8	$ 0.5
Interest Expense [Member] | Accounts Receivable Financing Arrangements [Member]
Schedule of Accounts Receivable, Net and Contract Assets and Liabilities [Line Items]
Non-recourse financing arrangements, discount charge	$ 1.9	$ 0.9
Minimum [Member]
Schedule of Accounts Receivable, Net and Contract Assets and Liabilities [Line Items]
Retainage, percent of contract billings	5.00%
Maximum [Member]
Schedule of Accounts Receivable, Net and Contract Assets and Liabilities [Line Items]
Retainage, percent of contract billings	10.00%

Property and Equipment, Net (Sc

Property and Equipment, Net (Schedule of Property and Equipment, Net) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property and Equipment [Line Items]
Property and equipment	$ 1,489,000	$ 1,455,600
Less accumulated depreciation and amortization	(779,200)	(749,100)
Property and equipment, net	709,806	706,506
Land [Member]
Property and Equipment [Line Items]
Property and equipment	4,600	4,600
Building and Leasehold Improvements [Member]
Property and Equipment [Line Items]
Property and equipment	26,600	26,700
Machinery and Equipment [Member]
Property and Equipment [Line Items]
Property and equipment	1,285,800	1,261,900
Office Furniture and Equipment [Member]
Property and Equipment [Line Items]
Property and equipment	156,900	149,900
Construction in Progress [Member]
Property and Equipment [Line Items]
Property and equipment	$ 15,100	$ 12,500

Property and Equipment, Net (Na

Property and Equipment, Net (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Property and Equipment [Line Items]
Capitalized internal-use software, gross	$ 113,800		$ 109,900
Capitalized internal-use software, net	25,000		$ 23,500
Depreciation and amortization	49,940	$ 42,904
Property and Equipment [Member]
Property and Equipment [Line Items]
Depreciation and amortization	$ 45,100	$ 38,800

Debt (Schedule of Carrying Valu

Debt (Schedule of Carrying Values of Debt) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Capital lease obligations	$ 187,500	$ 181,200
Total long-term debt obligations	1,442,400	1,381,600
Less unamortized deferred financing costs	(12,300)	(13,000)
Total debt, net of deferred financing costs	1,430,100	1,368,600
Current portion of long-term debt	86,558	87,866
Long-term debt	$ 1,343,549	1,280,706
Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maturity date	Feb. 22, 2022
Credit Facility [Member] | Revolving Loans [Member]
Debt Instrument [Line Items]
Long-term debt obligations	$ 453,800	377,700
Credit Facility [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Long-term debt obligations	391,900	396,900
Senior Notes [Member] | 4.875% Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt obligations	$ 400,000	400,000
Debt instrument, interest rate (percentage)	4.875%
Debt instrument, maturity date	Mar. 15, 2023
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Debt instrument, weighted average interest rate (percentage)	3.70%
Capital lease obligations, expiration date, range, end	Sep. 1, 2022
Other Debt Obligations [Member]
Debt Instrument [Line Items]
Long-term debt obligations	$ 9,200	$ 25,800

Debt (Senior Secured Credit Fac

Debt (Senior Secured Credit Facility) (Narrative) (Details) - Credit Facility [Member] - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2017	Mar. 31, 2018
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,500			$ 1,500
Line of credit facility, letters of credit issued	$ 131.7	$ 157.1	$ 157.1	$ 131.7
Line of credit facility, unused facility fee (percentage)	0.30%	0.25%
Line of credit facility, collateral				The Credit Facility is guaranteed by certain subsidiaries of the Company (the “Guarantor Subsidiaries”) and the obligations under the Credit Facility are secured by substantially all of the Company’s and the Guarantor Subsidiaries’ respective assets, subject to certain exceptions.
Revolving Loans [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,100			$ 1,100
Line of credit facility, amount of borrowings denominated in foreign currencies	112	$ 117	117	112
Line of credit facility, remaining borrowing capacity	514.5	565.2	565.2	514.5
Line of credit facility, remaining borrowing capacity available in either Canadian dollars or Mexican pesos	$ 187.7	$ 183.4	$ 183.4	$ 187.7
Revolving Loans [Member] | Weighted Average [Member]
Debt Instrument [Line Items]
Line of credit facility, interest rate (percentage)	3.98%	3.69%	3.69%	3.98%
Term Loan [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 400			$ 400
Line of credit facility, term loan, frequency of payments				quarterly
Line of credit facility, term loan, amount of quarterly principal installment payments			$ 3.1	$ 5
Line of credit facility, interest rate (percentage)	3.50%	3.07%	3.07%	3.50%
Letters of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, capacity available for letters of credit	$ 514.5	$ 492.9	$ 492.9	$ 514.5
Letters of Credit [Member] | Performance Standby [Member]
Debt Instrument [Line Items]
Line of credit facility, interest rate (percentage)	0.75%	0.625%	0.625%	0.75%
Letters of Credit [Member] | Commercial and/or Financial Standby [Member]
Debt Instrument [Line Items]
Line of credit facility, interest rate (percentage)	1.625%	1.50%	1.50%	1.625%

Debt (Other Credit Facilities)

Debt (Other Credit Facilities) (Narrative) (Details) - Other Credit Facilities [Member] $ in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018CAD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017CAD ($)	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity (in dollars)	$ 20		$ 20
Debt instrument, rationale for classification as long-term debt	Outstanding borrowings that are not renewed are repaid with borrowings under the Credit Facility. Accordingly, the carrying amounts of the Company’s borrowings under its other credit facilities, which are included within other debt obligations in the table above, are classified within long-term debt in the Company’s consolidated balance sheets.
Weighted Average [Member]
Debt Instrument [Line Items]
Line of credit facility, interest rate (percentage)	4.20%	4.20%	4.00%	4.00%
Canadian Dollars [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity (in dollars)		$ 15.5		$ 15.9
Long-term debt obligations (in dollars)		$ 6.4		$ 10.4

Debt (Debt Guarantees and Coven

Debt (Debt Guarantees and Covenants) (Narrative) (Details) - Senior Notes [Member] - 4.875% Senior Notes [Member]	3 Months Ended
	Mar. 31, 2018
Debt Instrument [Line Items]
Debt instrument, guarantees	The 4.875% Senior Notes are senior unsecured unsubordinated obligations and rank equal in right of payment with existing and future unsubordinated debt, and rank senior in right of payment to existing and future subordinated debt and are fully and unconditionally guaranteed on an unsecured, unsubordinated, joint and several basis by certain of the Company’s existing and future 100%-owned direct and indirect domestic subsidiaries that are each guarantors of the Credit Facility or other outstanding indebtedness.
Debt instrument, interest rate (percentage)	4.875%

Debt (Additional Information) (

Debt (Additional Information) (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Senior Notes [Member] | 4.875% Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate (percentage)	4.875%
Other Accrued Expenses [Member]
Debt Instrument [Line Items]
Debt instruments, accrued interest payable	$ 2.5	$ 7.4

Lease Obligations (Capital Leas

Lease Obligations (Capital Leases) (Narrative) (Details) - Property and Equipment [Member] - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Capital Leases [Line Items]
Assets held under capital lease, gross	$ 429.9	$ 418
Assets held under capital lease, net	$ 288.2	$ 277.3

Lease Obligations (Operating Le

Lease Obligations (Operating Leases) (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Lease Term in Excess of One Year [Member]
Operating Leased Assets [Line Items]
Operating leases, rent and related expense (in dollars)	$ 26.9	$ 25.6
Lease Term in Excess of One Year [Member] | Minimum [Member]
Operating Leased Assets [Line Items]
Operating leases, term of contract (in years)	1 year	1 year
Lease Term of One Year or Less [Member]
Operating Leased Assets [Line Items]
Operating leases, rent and related expense (in dollars)	$ 91.7	$ 55.1
Lease Term of One Year or Less [Member] | Maximum [Member]
Operating Leased Assets [Line Items]
Operating leases, term of contract (in years)	1 year	1 year

Stock-Based Compensation and 61

Stock-Based Compensation and Other Employee Benefit Plans (Narrative) (Details) shares in Millions	Mar. 31, 2018shares
Common Stock [Member]
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Stock-based compensation, number of shares available for future grant	4.7

Stock-Based Compensation and 62

Stock-Based Compensation and Other Employee Benefit Plans (Restricted Shares) (Narrative) (Details) - Restricted Shares [Member] - USD ($) $ in Millions	Mar. 31, 2018	Mar. 31, 2018	Mar. 31, 2017
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Stock-based compensation awards, unearned compensation	$ 23	$ 23
Stock-based compensation awards, unearned compensation, weighted average expected recognition period (in years)	2 years 2 months 12 days
Stock-based compensation, vested awards, intrinsic value		$ 0.1	$ 11.6

Stock-Based Compensation and 63

Stock-Based Compensation and Other Employee Benefit Plans (Schedule of Activity, Restricted Shares) (Details) - Common Stock [Member]	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Restricted Shares [Member]
Restricted Shares
Non-vested restricted shares, beginning balance (in shares)	1,448,591	[1]
Granted (in shares)	111,367
Vested (in shares)	(2,372)
Canceled/forfeited (in shares)	(6,552)
Non-vested restricted shares, ending balance (in shares)	1,551,034	[1]
Per Share Weighted Average Grant Date Fair Value
Non-vested restricted shares, per share weighted average grant date fair value, beginning balance (in dollars per share) | $ / shares	$ 23.29
Granted (in dollars per share) | $ / shares	50.83
Vested (in dollars per share) | $ / shares	50.60
Canceled/forfeited (in dollars per share) | $ / shares	22.23
Non-vested restricted shares, per share weighted average grant date fair value, ending balance (in dollars per share) | $ / shares	$ 25.23
Restricted Stock Units [Member]
Restricted Shares
Non-vested restricted shares, beginning balance (in shares)	27,550
Non-vested restricted shares, ending balance (in shares)	27,550
[1]	Includes 27,550 restricted stock units as of both March 31, 2018 and December 31, 2017, respectively.

Stock-Based Compensation and 64

Stock-Based Compensation and Other Employee Benefit Plans (Employee Stock Purchase Plans) (Narrative) (Details)	3 Months Ended
	Mar. 31, 2018
Employee Stock Purchase Plans [Member]
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Stock-based compensation plans, description	The Company has certain employee stock purchase plans (collectively, “ESPPs”) under which shares of the Company's common stock are available for purchase by eligible employees.

Stock-Based Compensation and 65

Stock-Based Compensation and Other Employee Benefit Plans (Schedule of Activity, Employee Stock Purchase Plans) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Common Stock [Member]
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Common shares issued (in shares)	25,638	24,026
Employee Stock Purchase Plans [Member]
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Cash proceeds (in dollars)	$ 1	$ 0.8
Employee Stock Purchase Plans [Member] | Common Stock [Member]
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Weighted average price per share (in dollars per share)	$ 39.99	$ 32.51
Weighted average per share grant date fair value (in dollars per share)	$ 9.79	$ 8.49

Stock-Based Compensation and 66

Stock-Based Compensation and Other Employee Benefit Plans (Schedule of Non-Cash Stock-Based Compensation Expense and Related Tax Effects) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Non-cash stock-based compensation expense		$ 3,182	$ 3,773
Income Tax Effects:
Income tax effect of non-cash stock-based compensation		800	1,200
Excess tax benefit from non-cash stock-based compensation	[1]	0	0
Net income tax effect		(11,126)	(27,358)
Share-Based Compensation [Member]
Income Tax Effects:
Net income tax effect			(200)
General and Administrative Expenses [Member]
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Non-cash stock-based compensation expense		$ 3,200	$ 3,800
[1]	Excess tax benefits represent cash flows from tax deductions in excess of the tax effect of compensation expense associated with share-based payment arrangements. For the three month period ended March 31, 2018, tax benefits, net of tax deficiencies, related to the vesting of share-based payment awards were de minimis, and, for the three month period ended March 31, 2017, the Company recognized a tax deficiency, net of tax benefits, of $0.2 million.

Other Retirement Plans (Narrati

Other Retirement Plans (Narrative) (Details)	3 Months Ended
	Mar. 31, 2018
Multiemployer Plans [Abstract]
Multiemployer plans, general nature	Certain of MasTec’s subsidiaries, including certain subsidiaries in Canada, contribute amounts to multiemployer pension and other multiemployer benefit plans and trusts (“MEPPs”), which are recorded as a component of employee wages and salaries within costs of revenue, excluding depreciation and amortization. Contributions are generally based on fixed amounts per hour per employee for employees covered under these plans. Multiemployer plan contribution rates are determined annually and assessed on a “pay-as-you-go” basis based on union employee payrolls.

Other Retirement Plans (Schedul

Other Retirement Plans (Schedule of Covered Employees and Contributions, Multiemployer Plans) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)employee	Mar. 31, 2017USD ($)employee
Covered Employees and Contributions, Multiemployer Plans [Line Items]
Multiemployer plans, contributions (in dollars)	$ 13.4	$ 6.3
Multiemployer Plans, Pension [Member]
Covered Employees and Contributions, Multiemployer Plans [Line Items]
Multiemployer plans, contributions (in dollars)	11.4	3.7
Multiemployer Plans, Other Multiemployer [Member]
Covered Employees and Contributions, Multiemployer Plans [Line Items]
Multiemployer plans, contributions (in dollars)	$ 2	$ 2.6
Workforce Subject to Collective Bargaining Arrangements [Member] | Unionized Employees [Member] | Low [Member]
Covered Employees and Contributions, Multiemployer Plans [Line Items]
Multiemployer plans, covered employees (in number of employees) | employee	2,018	550
Workforce Subject to Collective Bargaining Arrangements [Member] | Unionized Employees [Member] | High [Member]
Covered Employees and Contributions, Multiemployer Plans [Line Items]
Multiemployer plans, covered employees (in number of employees) | employee	2,612	3,669

Equity (Share Activity) (Narrat

Equity (Share Activity) (Narrative) (Details) - USD ($)	1 Months Ended	3 Months Ended
	Apr. 30, 2018	Mar. 31, 2018	Mar. 31, 2017
Equity, Treasury Stock [Line Items]
Payments for repurchase of common stock		$ 90,880,000	$ 0
2016 Share Repurchase Program [Member]
Equity, Treasury Stock [Line Items]
Treasury stock acquired, value		$ 98,400,000
2016 Share Repurchase Program [Member] | Subsequent Event [Member]
Equity, Treasury Stock [Line Items]
Payments for repurchase of common stock	$ 8,000,000
2016 Share Repurchase Program [Member] | Treasury Stock, Common [Member]
Equity, Treasury Stock [Line Items]
Treasury stock acquired (in shares)		2,000,000
2018 Share Repurchase Program [Member]
Equity, Treasury Stock [Line Items]
Share repurchase program, amount authorized, value		$ 100,000,000
2018 Share Repurchase Program [Member] | Subsequent Event [Member]
Equity, Treasury Stock [Line Items]
Treasury stock acquired, value	$ 24,500,000
2018 Share Repurchase Program [Member] | Treasury Stock, Common [Member]
Equity, Treasury Stock [Line Items]
Treasury stock acquired (in shares)		0
2018 Share Repurchase Program [Member] | Treasury Stock, Common [Member] | Subsequent Event [Member]
Equity, Treasury Stock [Line Items]
Treasury stock acquired (in shares)	600,000

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Quarterly provision for income taxes, description	In determining the quarterly provision for income taxes, management uses an estimated annual effective tax rate based on forecasted annual pre-tax income, permanent tax differences, statutory tax rates and tax planning opportunities in the various jurisdictions in which the Company operates. The effect of significant discrete items is separately recognized in the quarter(s) in which they occur.
U.S. corporate tax rate (percent)	21.00%		35.00%
Change in tax rate, non-cash tax benefit (in dollars)		$ 120.1

Segments and Related Informat71

Segments and Related Information (Narrative) (Details)	3 Months Ended
	Mar. 31, 2018segment
Segments and Related Information [Line Items]
Segment reporting information, factors used to identify entity's reportable segments	MasTec manages its operations under five operating segments, which represent MasTec’s five reportable segments: (1) Communications; (2) Oil and Gas; (3) Electrical Transmission; (4) Power Generation and Industrial and (5) Other. This structure is generally focused on broad end-user markets for MasTec’s labor-based construction services.
Number of operating segments	5
Number of reportable segments	5
Segment reporting information, description of products and services	All five reportable segments derive their revenue from the engineering, installation and maintenance of infrastructure, primarily in North America.
Segment reporting, description of all other segments	The Other segment includes equity investees, the services of which vary from those provided by the Company’s four primary segments, as well as other small business units that perform construction and other services for a variety of international end-markets.
Communications [Member]
Segments and Related Information [Line Items]
Segment reporting information, description of products and services	The Communications segment performs engineering, construction, maintenance and customer fulfillment activities related to communications infrastructure primarily for wireless and wireline/fiber communications and install-to-the-home customers, and, to a lesser extent, infrastructure for utilities, among others.
Oil and Gas [Member]
Segments and Related Information [Line Items]
Segment reporting information, description of products and services	MasTec performs engineering, construction and maintenance services on oil and natural gas pipelines and processing facilities for the energy and utilities industries through its Oil and Gas segment.
Electrical Transmission [Member]
Segments and Related Information [Line Items]
Segment reporting information, description of products and services	The Electrical Transmission segment primarily serves the energy and utility industries through the engineering, construction and maintenance of electrical transmission lines and substations.
Power Generation and Industrial [Member]
Segments and Related Information [Line Items]
Segment reporting information, description of products and services	The Power Generation and Industrial segment primarily serves energy, utility and other end-markets through the installation and construction of conventional and renewable power facilities, related electrical transmission infrastructure, ethanol/biofuel facilities and various types of heavy civil and industrial infrastructure.
Primary Segments [Member]
Segments and Related Information [Line Items]
Number of operating segments	4

Segments and Related Informat72

Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Revenue:
Revenue (in dollars)		$ 1,396,834	$ 1,158,184
Communications [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue		17.80%	13.40%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)	[1]	$ 627,100	$ 559,500
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)		536,500	455,900
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)		114,000	98,800
Reportable Segments [Member] | Power Generation and Industrial [Member]
Revenue:
Revenue (in dollars)		117,600	46,600
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)		1,900	1,700
Eliminations [Member]
Revenue:
Revenue (in dollars)		$ (300)	$ (4,300)
[1]	Revenue generated primarily by utilities customers represented 17.8% and 13.4% of Communications segment revenue for the three month periods ended March 31, 2018 and 2017, respectively.

Segments and Related Informat73

Segments and Related Information (Schedule of Financial Information by Reportable Segment - EBITDA) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
EBITDA:
EBITDA	$ 104.6	$ 123.5
Reportable Segments [Member] | Communications [Member]
EBITDA:
EBITDA	82.1	48.4
Reportable Segments [Member] | Oil and Gas [Member]
EBITDA:
EBITDA	33	93.9
Reportable Segments [Member] | Electrical Transmission [Member]
EBITDA:
EBITDA	4.6	3.2
Reportable Segments [Member] | Power Generation and Industrial [Member]
EBITDA:
EBITDA	4.8	0.8
Reportable Segments [Member] | Other [Member]
EBITDA:
EBITDA	5.9	(5.3)
Corporate [Member]
EBITDA:
EBITDA	$ (25.8)	$ (17.5)

Segments and Related Informat74

Segments and Related Information (Schedule of Financial Information by Reportable Segment - Depreciation and Amortization) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Depreciation and Amortization:
Depreciation and amortization	$ 49,940	$ 42,904
Reportable Segments [Member] | Communications [Member]
Depreciation and Amortization:
Depreciation and amortization	14,600	12,000
Reportable Segments [Member] | Oil and Gas [Member]
Depreciation and Amortization:
Depreciation and amortization	25,500	21,900
Reportable Segments [Member] | Electrical Transmission [Member]
Depreciation and Amortization:
Depreciation and amortization	5,300	5,800
Reportable Segments [Member] | Power Generation and Industrial [Member]
Depreciation and Amortization:
Depreciation and amortization	3,000	1,500
Reportable Segments [Member] | Other [Member]
Depreciation and Amortization:
Depreciation and amortization	0	0
Corporate [Member]
Depreciation and Amortization:
Depreciation and amortization	$ 1,500	$ 1,700

Segments and Related Informat75

Segments and Related Information (Reconciliation of Consolidated Income before Income Taxes to EBITDA) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
EBITDA Reconciliation:
Income before income taxes	$ 37,589	$ 67,985
Interest expense, net	17,058	12,597
Depreciation and amortization	49,940	42,904
Consolidated EBITDA	$ 104,600	$ 123,500

Segments and Related Informat76

Segments and Related Information (Foreign Operations) (Narrative) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Segments and Related Information [Line Items]
Revenue			$ 1,396,834	$ 1,158,184
Property and equipment, net	$ 709,806	$ 706,506	709,806
Intangible assets and goodwill, net	1,332,900	1,328,900	1,332,900
United States [Member]
Segments and Related Information [Line Items]
Revenue			1,400,000	1,100,000
Property and equipment, net	658,100	649,500	658,100
Intangible assets and goodwill, net	1,200,000	1,200,000	1,200,000
Foreign Operations [Member]
Segments and Related Information [Line Items]
Revenue			33,800	$ 59,200
Property and equipment, net	51,700	57,000	51,700
Intangible assets and goodwill, net	$ 109,500	$ 112,800	$ 109,500
Foreign Operations [Member] | Accounts Receivable, Net, Less BIEC [Member] | Geographic Concentration Risk [Member] | Foreign Customers [Member]
Segments and Related Information [Line Items]
Concentration risk, percentage of total	5.00%	5.00%

Segments and Related Informat77

Segments and Related Information (Schedule of Significant Customers, Revenue Concentration Information) (Details) - Customer Concentration Risk [Member] - Revenue [Member]		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Communications [Member] | AT&T (including DIRECTV) [Member]
Revenue, Significant Customers [Line Items]
Concentration risk, percentage of total	[1]	27.00%	36.00%
Oil and Gas [Member] | Energy Transfer Affiliates [Member]
Revenue, Significant Customers [Line Items]
Concentration risk, percentage of total	[2]	26.00%	17.00%
[1]	The Company’s relationship with AT&T is based upon multiple separate master service and other service agreements, including for installation and maintenance services, as well as construction/installation contracts for AT&T’s: (i) wireless business; (ii) wireline/fiber businesses; and (iii) various install-to-the-home businesses, including DIRECTV®. Revenue from AT&T is included in the Communications segment.
[2]	The Company's relationship with Energy Transfer affiliates is based upon various construction contracts for pipeline activities with Energy Transfer Partners L.P., and its subsidiaries and affiliates, all of which are consolidated by Energy Transfer Equity, L.P. Revenue from Energy Transfer affiliates is included in the Oil and Gas segment.

Commitments and Contingencies (

Commitments and Contingencies (Other Commitments and Contingencies) (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Self-Insurance [Member] | Workers' Compensation, General and Automobile Policies [Member]
Commitments and Contingencies [Line Items]
Self-insurance reserve	$ 111.8	$ 106.2
Self-Insurance [Member] | Workers' Compensation, General and Automobile Policies [Member] | Other Long-Term Liabilities [Member]
Commitments and Contingencies [Line Items]
Self-insurance reserve, non-current	76.6	72.2
Self-Insurance [Member] | Workers' Compensation, General and Automobile Policies [Member] | Other Long-Term Assets [Member] | Cash [Member]
Commitments and Contingencies [Line Items]
Cash collateral held by insurance carriers	1.6	1.6
Self-Insurance [Member] | Employee Group Medical Claims Policies [Member]
Commitments and Contingencies [Line Items]
Self-insurance reserve	2.4	2.6
Performance and Payment Bonds [Member] | Estimate [Member]
Commitments and Contingencies [Line Items]
Bonded projects, costs to complete	127.7	46
Performance and Payment Bonds [Member] | Subsidiaries [Member]
Commitments and Contingencies [Line Items]
Outstanding bonds, amount	129.6	119.7
Surety Bond [Member] | Self-Insurance [Member] | Workers' Compensation [Member]
Commitments and Contingencies [Line Items]
Outstanding bonds, amount	15.2	15.2
Credit Facility [Member]
Commitments and Contingencies [Line Items]
Letters of credit issued	131.7	157.1
Credit Facility [Member] | Financial Guarantees [Member] | Self-Insurance [Member] | Workers' Compensation, General and Automobile Policies [Member]
Commitments and Contingencies [Line Items]
Letters of credit issued	$ 88.9	$ 88.9

Commitments and Contingencies79

Commitments and Contingencies (Investment Arrangements) (Narrative) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Other Commitments [Line Items]
Cash, amounts held by proportionately consolidated non-controlled joint ventures	$ 40,235	$ 40,326	$ 15,687	$ 38,767
Joint Venture [Member]
Other Commitments [Line Items]
Cash, amounts held by proportionately consolidated non-controlled joint ventures	18,800	$ 17,300
Advances on project work, amounts due from joint ventures, current	$ 10,300
Joint Venture [Member] | Pacer [Member]
Other Commitments [Line Items]
Proportionately consolidated non-controlled joint venture, ownership percentage	35.00%
Joint Venture [Member] | Joint Ventures That Provide Electrical Transmission Infrastructure Services [Member] | Minimum [Member]
Other Commitments [Line Items]
Proportionately consolidated non-controlled joint venture, ownership percentage	85.00%
Joint Venture [Member] | Joint Ventures That Provide Electrical Transmission Infrastructure Services [Member] | Maximum [Member]
Other Commitments [Line Items]
Proportionately consolidated non-controlled joint venture, ownership percentage	90.00%

Commitments and Contingencies80

Commitments and Contingencies (Other Guarantees) (Narrative) (Details)	3 Months Ended
	Mar. 31, 2018
Other Guarantees [Line Items]
General warranty, description	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 [Member] | Minimum [Member]
Other Guarantees [Line Items]
Expected term or period (in years)	1 year
Warranty [Member] | Maximum [Member]
Other Guarantees [Line Items]
Expected term or period (in years)	2 years
Subsidiaries [Member]
Other Guarantees [Line Items]
Other guarantees, description	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.

Commitments and Contingencies81

Commitments and Contingencies (Concentrations of Risk) (Narrative) (Details) - customer	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Concentration Risk [Line Items]
Number of customers			350
Accounts Receivable, Net, Less BIEC [Member] | Credit Concentration Risk [Member] | Customer with Highest Net Accounts Receivable Position [Member]
Concentration Risk [Line Items]
Number of customers	1	1
Concentration risk, percentage of total	43.00%	46.00%
Accounts Receivable, Net, Less BIEC [Member] | Credit Concentration Risk [Member] | Customer with Second Highest Net Accounts Receivable Position [Member]
Concentration Risk [Line Items]
Concentration risk, percentage of total	16.00%	15.00%
Revenue [Member] | Customer Concentration Risk [Member] | Ten Largest Customers [Member]
Concentration Risk [Line Items]
Number of customers			10	10
Concentration risk, percentage of total			74.00%	76.00%

Related Party Transactions (Lea

Related Party Transactions (Leases and Other Transactions) (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended
	Feb. 28, 2018	Mar. 31, 2018	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2017
Management [Member] | 2017 Oil and Gas Acquisition [Member]
Related Party Transaction [Line Items]
Business combinations, cash paid (in dollars)				$ 40.6
Management [Member] | 2017 Oil and Gas Acquisition [Member] | Earn-Out Liabilities [Member]
Related Party Transaction [Line Items]
Business combinations, contingent consideration, liabilities (in dollars)		$ 59.9	$ 59.9
Management [Member] | Lease Agreements [Member]
Related Party Transaction [Line Items]
Payments, related party			7.5		$ 12.7
Payables, related party		3.4	3.4			$ 0.1
Management [Member] | Service Agreements [Member]
Related Party Transaction [Line Items]
Payments, related party			9		$ 6.6
Payables, related party		1.4	1.4			5.2
Management [Member] | Construction Contracts [Member]
Related Party Transaction [Line Items]
Revenue, related party			2.7
Receivables, related party		2	2			$ 0.6
Immediate Family Member of Management [Member] | Construction Management Firm Specializing in Steel Building Systems [Member]
Related Party Transaction [Line Items]
Business combinations, cash paid (in dollars)	$ 5.4
Business combinations, liabilities assumed, notes payable	$ 2.6
Repayments of notes payable		2.6
Immediate Family Member of Management [Member] | Construction Management Firm Specializing in Steel Building Systems [Member] | Earn-Out Liabilities [Member]
Related Party Transaction [Line Items]
Business combinations, contingent consideration, liabilities (in dollars)		$ 1.3	$ 1.3

Related Party Transactions (CCI

Related Party Transactions (CCI) (Narrative) (Details) - CCI [Member] - Immediate Family Member of Management [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Related Party Transaction [Line Items]
Equity investment, ownership percentage	15.00%
Equipment [Member]
Related Party Transaction [Line Items]
Payments, related party	$ 5.9	$ 1
Payables, related party	$ 3.4

Related Party Transactions (Sub

Related Party Transactions (Subcontracting Arrangements and Other Transactions) (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)employee	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
Management [Member] | Subcontracting Arrangements [Member] | Related Contractor or Supplier [Member]
Related Party Transaction [Line Items]
Number of additional management employees, subcontracting arrangement | employee	2
Payments or expenses, related party	$ 5	$ 0.6
Payables, related party	1		$ 2
Management [Member] | Service Agreements [Member]
Related Party Transaction [Line Items]
Payments or expenses, related party	9	6.6
Payables, related party	1.4		5.2
Management [Member] | Lease Agreements [Member]
Related Party Transaction [Line Items]
Payments or expenses, related party	7.5	12.7
Payables, related party	3.4		0.1
Executive Officers [Member] | Employee Leasing Arrangements [Member] | Related Customer [Member]
Related Party Transaction [Line Items]
Charges, related party	0.2	0.2
Receivables, related party	0.2		0.2
Executive Officers [Member] | Service Agreements [Member] | Related Customer [Member]
Related Party Transaction [Line Items]
Revenue, related parties	0.3	0.2
Receivables, related party	0.3		$ 0.3
Chairman, Board of Directors [Member] | Lease Agreements [Member] | Aircraft [Member]
Related Party Transaction [Line Items]
Payments or expenses, related party	$ 0.5	$ 0.5

Related Party Transactions (Equ

Related Party Transactions (Equity Method Investment) (Narrative) (Details) - Related Party Investment [Member] - Equity Method Investee [Member] - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Equity investment, ownership percentage	40.00%
Amounts outstanding, net, related party	$ 0.3	$ 0.3

Related Party Transactions (Con

Related Party Transactions (Contractual Joint Venture) (Narrative) (Details) - Joint Venture [Member] - Pacer [Member] $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)	Mar. 31, 2018CAD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017CAD ($)	Dec. 31, 2017USD ($)
Related Party Transaction [Line Items]
Proportionately consolidated non-controlled joint venture, ownership percentage			35.00%	35.00%
Performance Guarantee [Member]
Related Party Transaction [Line Items]
Guarantees issued, related party			$ 132.1		$ 132.1
Canadian Dollars [Member]
Related Party Transaction [Line Items]
Revenue, related parties	$ 300,000	$ 100,000
Accounts receivable, net of BIEC, related parties				$ 700,000		$ 800,000
Canadian Dollars [Member] | Financing Support [Member]
Related Party Transaction [Line Items]
Financing or amounts advanced, related party	$ 600,000	$ 800,000
Amounts committed, related party				0
Canadian Dollars [Member] | Performance Guarantee [Member]
Related Party Transaction [Line Items]
Guarantees issued, related party				$ 102,400,000		$ 105,100,000

Related Party Transactions (Non

Related Party Transactions (Non-Controlling Interests) (Narrative) (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Oct. 31, 2017USD ($)	Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)
Related Party Transaction [Line Items]
Distributions to non-controlling interests		$ 559	$ 1,280
Management [Member]
Related Party Transaction [Line Items]
Payments to acquire remaining non-controlling interests	$ 21,400
Distributions to non-controlling interests		600	$ 1,300
Management [Member] | Acquisition of Non-Controlling Interests [Member]
Related Party Transaction [Line Items]
Number of subsidiaries, non-controlling interests	1
Management [Member] | Acquisition of Non-Controlling Interests [Member] | Earn-Out Liabilities [Member]
Related Party Transaction [Line Items]
Fair value of contingent consideration (earn-out liability)		$ 9,000

Related Party Transactions (Spl

Related Party Transactions (Split Dollar Agreements) (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Chief Executive Officer [Member]
Related Party Transaction [Line Items]
Payments for life insurance policies	$ 0	$ 0
Chairman, Board of Directors [Member]
Related Party Transaction [Line Items]
Payments for life insurance policies	0	$ 0
Executive Officers [Member] | Other Long-Term Assets [Member]
Related Party Transaction [Line Items]
Life insurance assets, carrying amount	$ 16,600,000		$ 16,600,000

Supplemental Guarantor Financ89

Supplemental Guarantor Financial Information (Narrative) (Details)	Mar. 31, 2018
Senior Notes [Member] | 4.875% Senior Notes [Member]
Condensed Unaudited Consolidating Financial Information [Line Items]
Debt instrument, interest rate (percentage)	4.875%

Supplemental Guarantor Financ90

Supplemental Guarantor Financial Information (Condensed Unaudited Consolidating Statements of Operations and Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Condensed Unaudited Consolidating Statements of Operations and Comprehensive Income (Loss) [Line Items]
Revenue		$ 1,396,834	$ 1,158,184
Costs of revenue, excluding depreciation and amortization		1,237,299	971,134
Depreciation and amortization		49,940	42,904
General and administrative expenses		63,622	64,781
Interest expense (income), net		17,058	12,597
Equity in earnings of unconsolidated affiliates		(5,585)	(1,646)
Other (income) expense, net		(3,089)	429
Income before income taxes		37,589	67,985
(Provision for) benefit from income taxes		(11,126)	(27,358)
Net income (loss) before equity in income from subsidiaries		26,500	40,600
Equity in income (losses) from subsidiaries, net of tax		0	0
Net income		26,463	40,627
Net loss attributable to non-controlling interests		(97)	(343)
Net income attributable to MasTec, Inc.	[1]	26,560	40,970
Comprehensive income (loss)		33,656	42,441
Reportable Legal Entities [Member] | MasTec, Inc. [Member]
Condensed Unaudited Consolidating Statements of Operations and Comprehensive Income (Loss) [Line Items]
Revenue		0	0
Costs of revenue, excluding depreciation and amortization		0	0
Depreciation and amortization		0	0
General and administrative expenses		800	600
Interest expense (income), net		0	0
Equity in earnings of unconsolidated affiliates		0	0
Other (income) expense, net		0	0
Income before income taxes		(800)	(600)
(Provision for) benefit from income taxes		200	200
Net income (loss) before equity in income from subsidiaries		(600)	(400)
Equity in income (losses) from subsidiaries, net of tax		27,100	41,400
Net income		26,500	41,000
Net loss attributable to non-controlling interests		0	0
Net income attributable to MasTec, Inc.		26,500	41,000
Comprehensive income (loss)		33,800	42,800
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Unaudited Consolidating Statements of Operations and Comprehensive Income (Loss) [Line Items]
Revenue		1,265,600	1,083,200
Costs of revenue, excluding depreciation and amortization		1,136,200	888,700
Depreciation and amortization		43,300	35,300
General and administrative expenses		59,200	59,600
Interest expense (income), net		32,900	27,900
Equity in earnings of unconsolidated affiliates		0	0
Other (income) expense, net		(2,600)	0
Income before income taxes		(3,400)	71,700
(Provision for) benefit from income taxes		800	(26,300)
Net income (loss) before equity in income from subsidiaries		(2,600)	45,400
Equity in income (losses) from subsidiaries, net of tax		0	0
Net income		(2,600)	45,400
Net loss attributable to non-controlling interests		0	(100)
Net income attributable to MasTec, Inc.		(2,600)	45,500
Comprehensive income (loss)		(2,600)	45,500
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Unaudited Consolidating Statements of Operations and Comprehensive Income (Loss) [Line Items]
Revenue		185,600	87,900
Costs of revenue, excluding depreciation and amortization		155,500	95,300
Depreciation and amortization		6,600	7,600
General and administrative expenses		3,600	4,600
Interest expense (income), net		(15,800)	(15,300)
Equity in earnings of unconsolidated affiliates		(5,600)	(1,600)
Other (income) expense, net		(500)	400
Income before income taxes		41,800	(3,100)
(Provision for) benefit from income taxes		(12,100)	(1,300)
Net income (loss) before equity in income from subsidiaries		29,700	(4,400)
Equity in income (losses) from subsidiaries, net of tax		0	0
Net income		29,700	(4,400)
Net loss attributable to non-controlling interests		(100)	(200)
Net income attributable to MasTec, Inc.		29,800	(4,200)
Comprehensive income (loss)		36,800	(2,700)
Eliminations [Member]
Condensed Unaudited Consolidating Statements of Operations and Comprehensive Income (Loss) [Line Items]
Revenue		(54,400)	(12,900)
Costs of revenue, excluding depreciation and amortization		(54,400)	(12,900)
Depreciation and amortization		0	0
General and administrative expenses		0	0
Interest expense (income), net		0	0
Equity in earnings of unconsolidated affiliates		0	0
Other (income) expense, net		0	0
Income before income taxes		0	0
(Provision for) benefit from income taxes		0	0
Net income (loss) before equity in income from subsidiaries		0	0
Equity in income (losses) from subsidiaries, net of tax		(27,100)	(41,400)
Net income		(27,100)	(41,400)
Net loss attributable to non-controlling interests		0	0
Net income attributable to MasTec, Inc.		(27,100)	(41,400)
Comprehensive income (loss)		$ (34,300)	$ (43,200)
[1]	Calculated as total net income less amounts attributable to non-controlling interests.

Supplemental Guarantor Financ91

Supplemental Guarantor Financial Information (Condensed Unaudited Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets
Total current assets	$ 1,907,595	$ 1,852,366
Property and equipment, net	709,806	706,506
Goodwill and other intangible assets, net	1,332,900	1,328,900
Investments in and advances to consolidated affiliates, net	0	0
Other long-term assets	204,071	178,824
Total assets	4,154,348	4,066,576
Liabilities and equity
Total current liabilities	1,047,340	963,827
Long-term debt	1,343,549	1,280,706
Other long-term liabilities	389,300	388,700
Total liabilities	2,780,151	2,633,223
Total equity	1,374,197	1,433,353
Total liabilities and equity	4,154,348	4,066,576
Reportable Legal Entities [Member] | MasTec, Inc. [Member]
Assets
Total current assets	0	0
Property and equipment, net	0	0
Goodwill and other intangible assets, net	0	0
Investments in and advances to consolidated affiliates, net	1,356,000	1,415,000
Other long-term assets	15,700	15,800
Total assets	1,371,700	1,430,800
Liabilities and equity
Total current liabilities	0	0
Long-term debt	0	0
Other long-term liabilities	0	0
Total liabilities	0	0
Total equity	1,371,700	1,430,800
Total liabilities and equity	1,371,700	1,430,800
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Assets
Total current assets	1,641,500	1,536,600
Property and equipment, net	648,200	638,700
Goodwill and other intangible assets, net	1,195,600	1,187,900
Investments in and advances to consolidated affiliates, net	1,016,600	847,700
Other long-term assets	23,800	23,400
Total assets	4,525,700	4,234,300
Liabilities and equity
Total current liabilities	996,700	778,600
Long-term debt	1,336,000	1,269,400
Other long-term liabilities	380,400	379,900
Total liabilities	2,713,100	2,427,900
Total equity	1,812,600	1,806,400
Total liabilities and equity	4,525,700	4,234,300
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Assets
Total current assets	376,600	332,900
Property and equipment, net	61,600	67,800
Goodwill and other intangible assets, net	137,300	141,000
Investments in and advances to consolidated affiliates, net	702,500	746,600
Other long-term assets	164,500	139,600
Total assets	1,442,500	1,427,900
Liabilities and equity
Total current liabilities	161,100	202,300
Long-term debt	7,500	11,300
Other long-term liabilities	8,900	8,800
Total liabilities	177,500	222,400
Total equity	1,265,000	1,205,500
Total liabilities and equity	1,442,500	1,427,900
Eliminations [Member]
Assets
Total current assets	(110,500)	(17,100)
Property and equipment, net	0	0
Goodwill and other intangible assets, net	0	0
Investments in and advances to consolidated affiliates, net	(3,075,100)	(3,009,300)
Other long-term assets	0	0
Total assets	(3,185,600)	(3,026,400)
Liabilities and equity
Total current liabilities	(110,500)	(17,100)
Long-term debt	0	0
Other long-term liabilities	0	0
Total liabilities	(110,500)	(17,100)
Total equity	(3,075,100)	(3,009,300)
Total liabilities and equity	$ (3,185,600)	$ (3,026,400)

Supplemental Guarantor Financ92

Supplemental Guarantor Financial Information (Condensed Unaudited Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Unaudited Consolidating Statements of Cash Flows [Line Items]
Net cash provided by (used in) operating activities	$ 83,501	$ 154,173
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	(4,329)	0
Capital expenditures	(22,545)	(28,901)
Proceeds from sale of property and equipment	5,382	511
Payments for other investments	(14,779)	(53,347)
Proceeds from other investments	5,415	12,118
Net cash used in investing activities	(30,856)	(69,619)
Cash flows from financing activities:
Proceeds from credit facilities	816,888	361,743
Repayments of credit facilities	(747,099)	(447,112)
Repayments of other borrowings and capital lease obligations	(32,700)	(14,400)
Repurchase of common stock	(90,880)	0
Distributions to non-controlling interests	(559)	(1,280)
Proceeds from stock-based awards, net	916
Payments for stock-based awards, net		(761)
Other financing activities	0	(5,973)
Net financing activities and advances from (to) consolidated affiliates	0	0
Net cash used in financing activities	(53,458)	(107,794)
Effect of currency translation on cash	722	160
Net decrease in cash and cash equivalents	(91)	(23,080)
Cash and cash equivalents - beginning of period	40,326	38,767
Cash and cash equivalents - end of period	40,235	15,687
Reportable Legal Entities [Member] | MasTec, Inc. [Member]
Condensed Unaudited Consolidating Statements of Cash Flows [Line Items]
Net cash provided by (used in) operating activities	0	0
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	0	0
Capital expenditures	0	0
Proceeds from sale of property and equipment	0	0
Payments for other investments	0	0
Proceeds from other investments	0	0
Net cash used in investing activities	0	0
Cash flows from financing activities:
Proceeds from credit facilities	0	0
Repayments of credit facilities	0	0
Repayments of other borrowings and capital lease obligations	0	0
Repurchase of common stock	(90,900)
Distributions to non-controlling interests	0	0
Proceeds from stock-based awards, net	900
Payments for stock-based awards, net		(800)
Other financing activities		0
Net financing activities and advances from (to) consolidated affiliates	90,000	800
Net cash used in financing activities	0	0
Effect of currency translation on cash	0	0
Net decrease in cash and cash equivalents	0	0
Cash and cash equivalents - beginning of period	0	0
Cash and cash equivalents - end of period	0	0
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Unaudited Consolidating Statements of Cash Flows [Line Items]
Net cash provided by (used in) operating activities	114,000	179,500
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	(4,300)	0
Capital expenditures	(22,400)	(27,800)
Proceeds from sale of property and equipment	4,800	400
Payments for other investments	0	0
Proceeds from other investments	0	0
Net cash used in investing activities	(21,900)	(27,400)
Cash flows from financing activities:
Proceeds from credit facilities	810,600	357,200
Repayments of credit facilities	(736,600)	(439,000)
Repayments of other borrowings and capital lease obligations	(30,600)	(12,000)
Repurchase of common stock	0
Distributions to non-controlling interests	(600)	(1,300)
Proceeds from stock-based awards, net	0
Payments for stock-based awards, net		0
Other financing activities		(6,000)
Net financing activities and advances from (to) consolidated affiliates	(132,300)	(78,800)
Net cash used in financing activities	(89,500)	(179,900)
Effect of currency translation on cash	0	0
Net decrease in cash and cash equivalents	2,600	(27,800)
Cash and cash equivalents - beginning of period	10,000	28,900
Cash and cash equivalents - end of period	12,600	1,100
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Unaudited Consolidating Statements of Cash Flows [Line Items]
Net cash provided by (used in) operating activities	(30,500)	(25,300)
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	0	0
Capital expenditures	(100)	(1,100)
Proceeds from sale of property and equipment	600	100
Payments for other investments	(14,800)	(53,300)
Proceeds from other investments	5,400	12,100
Net cash used in investing activities	(8,900)	(42,200)
Cash flows from financing activities:
Proceeds from credit facilities	6,300	4,500
Repayments of credit facilities	(10,500)	(8,100)
Repayments of other borrowings and capital lease obligations	(2,100)	(2,300)
Repurchase of common stock	0
Distributions to non-controlling interests	0	0
Proceeds from stock-based awards, net	0
Payments for stock-based awards, net		0
Other financing activities		0
Net financing activities and advances from (to) consolidated affiliates	42,300	78,000
Net cash used in financing activities	36,000	72,100
Effect of currency translation on cash	700	200
Net decrease in cash and cash equivalents	(2,700)	4,800
Cash and cash equivalents - beginning of period	30,300	9,900
Cash and cash equivalents - end of period	27,600	14,700
Eliminations [Member]
Condensed Unaudited Consolidating Statements of Cash Flows [Line Items]
Net cash provided by (used in) operating activities	0	0
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	0	0
Capital expenditures	0	0
Proceeds from sale of property and equipment	0	0
Payments for other investments	0	0
Proceeds from other investments	0	0
Net cash used in investing activities	0	0
Cash flows from financing activities:
Proceeds from credit facilities	0	0
Repayments of credit facilities	0	0
Repayments of other borrowings and capital lease obligations	0	0
Repurchase of common stock	0
Distributions to non-controlling interests	0	0
Proceeds from stock-based awards, net	0
Payments for stock-based awards, net		0
Other financing activities		0
Net financing activities and advances from (to) consolidated affiliates	0	0
Net cash used in financing activities	0	0
Effect of currency translation on cash	0	0
Net decrease in cash and cash equivalents	0	0
Cash and cash equivalents - beginning of period	0	0
Cash and cash equivalents - end of period	$ 0	$ 0