Goodwill and Other Intangible Assets (Schedule of Unaudited Supplemental Pro Forma Information) (Details) - USD ($) $ in Millions		3 Months Ended					12 Months Ended
		Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Business combinations, pro forma information, description							The unaudited supplemental pro forma financial information presented below has been prepared by adjusting the historical results of MasTec to include the historical results of the acquired businesses described above, and was then adjusted (i) to remove acquisition costs, including certain acquisition integration costs; (ii) to increase amortization expense resulting from the incremental intangible assets acquired; (iii) to increase interest expense as a result of the cash consideration paid; (iv) to remove integration-related employee redundancy costs; and (v) to reduce interest expense from debt repaid upon acquisition of the respective businesses. The unaudited supplemental pro forma financial information does not include adjustments to reflect the impact of other cost savings or synergies that may have resulted from these acquisitions.
Unaudited Supplemental Pro Forma Financial Information and Results of Businesses Acquired
Business combinations, pro forma revenue									$ 5,085.2
Business combinations, pro forma net income from continuing operations									130.3
Business combinations, actual of acquirees, revenue (year-over-year impact)								$ 301.5	565.4
Business combinations, actual of acquirees, net (loss) income from continuing operations (year-over-year impact)	[1]							(13.4)	0.7
General and Administrative Expenses [Member]
Unaudited Supplemental Pro Forma Financial Information and Results of Businesses Acquired
Business combinations, other acquisition-related costs								11.2	2.7
Communications [Member]
Unaudited Supplemental Pro Forma Financial Information and Results of Businesses Acquired
Business combinations, acquisition integration costs				$ 1.2	$ 7.8	$ 8.8		17.8	5.3
Communications [Member] | General and Administrative Expenses [Member]
Unaudited Supplemental Pro Forma Financial Information and Results of Businesses Acquired
Business combinations, acquisition integration costs								17.8	5.3
Communications [Member] | WesTower [Member] | General and Administrative Expenses [Member]
Unaudited Supplemental Pro Forma Financial Information and Results of Businesses Acquired
Business combinations, acquisition integration costs								9.3	$ 5.0
Other [Member] | Pacer [Member] | Joint Venture [Member] | Canadian Dollars [Member] | Contracts Accounted for under Percentage-of-Completion [Member]
Unaudited Supplemental Pro Forma Financial Information and Results of Businesses Acquired
Project losses		$ 5.1	$ 8.0	$ 2.8		$ 5.5	$ 5.1	$ 16.3

[1] Acquiree net (loss) income from continuing operations for the years ended December 31, 2015 and 2014 includes approximately $9.3 million and $5.0 million, respectively, of pre-tax acquisition integration costs incurred in connection with the WesTower acquisition and, for the year ended December 31, 2015, includes project losses of $16.3 million associated with the Company’s proportionate interest in a non-controlled Canadian joint venture. Other acquisition-related costs, including certain acquisition integration costs totaling $11.2 million and $2.7 million for the years ended December 31, 2015 and 2014, respectively, which are included within general and administrative expenses in the Company’s consolidated statements of operations, are not included in the above presented acquiree results for the respective periods. The above results also do not include interest expense associated with consideration paid for these acquisitions.