Acquisitions (2014 Acquisitions - WesTower) (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Oct. 01, 2014
Communications [Member]
Business Combinations [Line Items]
Business combinations, acquisition integration costs	$ 8,800,000
Communications [Member] | General and Administrative Expenses [Member]
Business Combinations [Line Items]
Business combinations, acquisition integration costs	$ 8,800,000	$ 5,300,000
WesTower [Member]
Business Combinations [Line Items]
Business combinations, effective date	Oct. 01, 2014
Business combinations, percentage of voting interests acquired	100.00%
Business combinations, name of acquired entity	WesTower Communications Inc. (“WesTower”)
Business combinations, description of acquired entity	WesTower is a telecommunications services firm focusing on construction and maintenance of communications infrastructure related to wireless networks throughout the United States. WesTower, which provides services to a number of major wireless carriers throughout the Eastern, Central and Western United States, is expected to expand the Company’s geographical presence, market penetration and skilled employee base within its existing wireless operations.
Business combinations, goodwill recognized, description	Goodwill arising from the acquisition represents the estimated value of WesTower’s geographic presence in key high growth markets, its assembled workforce and synergies expected to be achieved from the combined operations of WesTower and MasTec.
Business combinations, goodwill, expected tax deductible amount			$ 0
WesTower [Member] | Current Liabilities [Member]
Business Combinations [Line Items]
Business combinations, acquisition integration costs, current liabilities	$ 2,300,000	$ 3,500,000
WesTower [Member] | Communications [Member] | General and Administrative Expenses [Member]
Business Combinations [Line Items]
Business combinations, acquisition integration costs	$ 5,700,000