Acquisitions (Schedule of Business Acquisition Pro Forma Information, Business Acquisitions) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Business Combinations [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 result from these acquisitions.
Unaudited Pro Forma Financial Information and Results of Businesses Acquired
Business combinations, pro forma revenue			$ 1,423.5		$ 3,854.0
Business combinations, pro forma net income from continuing operations			50.6		100.2
Business combinations, actual of acquirees, revenue (year-over-year impact)		$ 69.2	133.2	$ 301.5	342.5
Business combinations, actual of acquirees, net income (loss) from continuing operations (year-over-year impact)	[1]	0.2	2.3	(13.4)	4.3
General and Administrative Expenses [Member]
Unaudited Pro Forma Financial Information and Results of Businesses Acquired
Business combinations, acquisition and integration-related costs		1.9		10.3
Business combinations, other acquisition-related costs			$ 0.5		$ 2.0
Communications [Member]
Unaudited Pro Forma Financial Information and Results of Businesses Acquired
Business combinations, acquisition integration costs		1.2		17.8
Communications [Member] | General and Administrative Expenses [Member]
Unaudited Pro Forma Financial Information and Results of Businesses Acquired
Business combinations, acquisition integration costs		1.2		17.8
Communications [Member] | WesTower [Member] | General and Administrative Expenses [Member]
Unaudited Pro Forma Financial Information and Results of Businesses Acquired
Business combinations, acquisition integration costs				9.3
Other [Member] | Pacer [Member] | Joint Venture [Member] | Canadian Dollars [Member] | Contracts Accounted for under Percentage-of-Completion [Member]
Unaudited Pro Forma Financial Information and Results of Businesses Acquired
Project losses		$ 2.8		$ 8.3

[1] Acquiree net income (loss) from continuing operations for the nine month period ended September 30, 2015 includes approximately $9.3 million of pre-tax acquisition integration costs incurred in connection with the WesTower acquisition, and for the three and nine month periods ended September 30, 2015, includes project losses of $2.8 million and $8.3 million, respectively, associated with the Company’s proportionate interest in a non-controlled Canadian joint venture. Other acquisition-related costs, including certain acquisition integration costs totaling $1.9 million and $10.3 million for the three and nine month periods ended September 30, 2015, respectively, and $0.5 million and $2.0 million for the three and nine month periods ended September 30, 2014, respectively, 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.