Goodwill and Other Intangible Assets (Pro Forma Financial Information and Acquisition Results) (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pro Forma Financial Information and Acquisition Results [Abstract]
Business combinations, unaudited supplemental pro forma revenue	$ 1,518.3	$ 1,445.6
Business combinations, unaudited supplemental pro forma net income	$ 43.3	28.5
Business combinations, unaudited pro forma information, description	These unaudited pro forma financial results include the results of operations of the acquired companies 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 unaudited historical results of the acquired businesses described above, and then adjusted for (i) acquisition costs; (ii) amortization expense resulting from the acquired intangible assets; (iii) interest expense as a result of the cash consideration paid; (iv) interest expense from debt repaid upon acquisition; and (iv) other purchase accounting related adjustments. 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, consolidated acquisition-related revenue	$ 39.7	76.8
Business combinations, consolidated acquisition-related income (loss)	$ (6.1)	$ 2.0