Earnings Per Share (Narrative) (Details) - shares shares in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2018
Earnings Per Share [Line Items]
Computation of earnings per share, methodology		Basic earnings or loss per share is computed by dividing net income 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 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.
Effect of share repurchases, decrease in weighted average shares outstanding (in shares)	3.5	2.1
Treasury Stock, Common [Member]
Earnings Per Share [Line Items]
Treasury stock acquired (in shares)	1.6	4.3

Disclosure of the methodology and assumptions used in the reconciliation of earnings per share, which may include the individual income and share amount effects of all securities that affect earnings per share, the effect that has been given to preferred dividends in arriving at income available to common stockholders in computing basic earnings per share, securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic EPS in the future that were not included in the computation of diluted EPS because to do so would have been antidilutive for the period(s) presented and a description of any transaction that occurs after the end of the most recent period but before issuance of the financial statements that would have changed materially the number of common shares or potential common shares outstanding at the end of the period if the transaction had occurred before the end of the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

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