Acquisitions (2014 Acquisitions - Pacer) (Narrative) (Details)		1 Months Ended	3 Months Ended			10 Months Ended	12 Months Ended
		Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)	May. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2015 CAD	Dec. 31, 2015 USD ($)	Dec. 31, 2014 CAD	Dec. 31, 2014 USD ($)	Jun. 01, 2014 USD ($)
Business Combinations [Line Items]
Financing commitments, amounts paid							$ 127,480,000		$ 4,092,000	$ 16,173,000
Other current liabilities, equity method investments (in dollars)												$ 43,459,000		$ 66,527,000
Other current assets, equity method investments												68,190,000		44,463,000
Business combinations, measurement period adjustments, goodwill increase (decrease)	[1]						(3,600,000)
Goodwill and intangible asset impairment							$ 78,625,000		0	$ 0
Performance Guarantees [Member]
Business Combinations [Line Items]
Guarantees issued, related parties												$ 539,300,000		748,300,000
Pacer [Member]
Business Combinations [Line Items]
Business combinations, effective date							Jun. 01, 2014
Business combinations, percentage of voting interests acquired											100.00%	100.00%
Business combinations, name of acquired entity							Pacer Construction Holdings Corporation and its affiliated operating companies (collectively, “Pacer”)
Business combinations, description of acquired entity							Pacer is a western Canadian civil construction services company, headquartered in Calgary, Alberta, Canada.  Pacer’s services include infrastructure construction primarily in support of oil and gas production, processing, mining and transportation.
Business combinations, goodwill recognized, description							Goodwill arising from the acquisition represents the estimated value of Pacer’s geographic presence in key high-growth Canadian markets, its assembled workforce, its management team’s industry-specific project management expertise and synergies expected to be achieved from the combined operations of Pacer and MasTec.
Goodwill and intangible asset impairment			$ 78,600,000
Business combinations, goodwill, expected tax deductible amount															$ 0
Pacer [Member] | Earn-Out Arrangements [Member]
Business Combinations [Line Items]
Business combinations, contingent consideration arrangements, basis for amount							The contingent consideration included in the table above equals 25% of the excess, if any, of Pacer’s expected earnings from continuing operations before interest, taxes, depreciation and amortization (“EBITDA”) above certain thresholds for a five-year period, as set forth in the purchase agreement, and is payable annually in Canadian dollars.
Business combinations, contingent consideration, percentage of excess EBITDA							25.00%
Business combinations, contingent consideration, earn-out period (in years)							5 years
Business combinations, contingent consideration, fair value measurements, significant assumptions							The fair value of the earn-out liability was estimated using an income approach and incorporated significant inputs not observable in the market. Key assumptions in the estimated valuation included the discount rate and probability-weighted EBITDA projections.
Business combination, contingent consideration arrangements, range of outcomes, value, low | CAD											CAD 0
Business combination, contingent consideration arrangements, range of outcomes, value, high | CAD											71,000,000
Pacer [Member] | Joint Venture [Member] | Performance Guarantees [Member]
Business Combinations [Line Items]
Guarantees issued, related parties | CAD											CAD 132,100,000		CAD 132,100,000
Pacer [Member] | Joint Venture [Member] | Other [Member] | Performance Guarantees [Member] | Minimum [Member]
Business Combinations [Line Items]
Construction projects, percentage complete											50.00%	50.00%
Pacer [Member] | Equity Method Investee [Member] | Pacer Equity Method Investee in Receivership [Member]
Business Combinations [Line Items]
Equity method investment, expected collection period (in years)							12 months
Pacer [Member] | Equity Method Investee [Member] | Performance Guarantees [Member]
Business Combinations [Line Items]
Construction projects, percentage complete											100.00%	100.00%
Pacer [Member] | Equity Method Investee [Member] | Guarantee of Indebtedness of Others [Member] | Financial Support [Member] | Pacer Equity Method Investee in Receivership [Member] | Revolving Loans [Member]
Business Combinations [Line Items]
Number of equity method investments in which the company will cease participation											1	1
Pacer [Member] | Canadian Dollars [Member]
Business Combinations [Line Items]
Business combinations, measurement period adjustments, property and equipment increase (decrease)								$ 8,400,000
Business combinations, measurement period adjustments, goodwill increase (decrease)								47,500,000
Pacer [Member] | Canadian Dollars [Member] | Earn-Out Arrangements [Member]
Business Combinations [Line Items]
Business combination, contingent consideration arrangements, range of outcomes, value, low												$ 0
Business combination, contingent consideration arrangements, range of outcomes, value, high												52,000,000
Pacer [Member] | Canadian Dollars [Member] | Equity Method Investments [Member]
Business Combinations [Line Items]
Net equity method investment obligations, financing arrangements															$ 31,000,000
Pacer [Member] | Canadian Dollars [Member] | Current Liabilities [Member]
Business Combinations [Line Items]
Business combinations, measurement period adjustments, liabilities increase (decrease)								5,600,000
Pacer [Member] | Canadian Dollars [Member] | Long-Term Deferred Tax Liabilities [Member]
Business Combinations [Line Items]
Business combinations, measurement period adjustments, liabilities increase (decrease)								1,200,000
Pacer [Member] | Canadian Dollars [Member] | Equity Method Investments [Member]
Business Combinations [Line Items]
Business combinations, measurement period adjustments, assets increase (decrease)								$ (49,000,000)
Pacer [Member] | Canadian Dollars [Member] | Joint Venture [Member]
Business Combinations [Line Items]
Revenue, related parties, affiliates							$ 2,100,000		1,700,000
Pacer [Member] | Canadian Dollars [Member] | Joint Venture [Member] | Financial Support [Member]
Business Combinations [Line Items]
Financing commitments, amounts paid							8,200,000		0
Unconsolidated affiliates, outstanding commitments												0
Pacer [Member] | Canadian Dollars [Member] | Joint Venture [Member] | Accounts Receivable [Member]
Business Combinations [Line Items]
Receivables, related parties, unincorporated joint venture												1,200,000		1,800,000
Pacer [Member] | Canadian Dollars [Member] | Joint Venture [Member] | Performance Guarantees [Member]
Business Combinations [Line Items]
Guarantees issued, related parties												95,400,000		113,600,000
Pacer [Member] | Canadian Dollars [Member] | Joint Venture [Member] | Other [Member] | Contracts Accounted for under Percentage-of-Completion [Member]
Business Combinations [Line Items]
Project losses (in dollars)			$ 8,000,000	$ 2,800,000	$ 5,500,000		16,300,000
Pacer [Member] | Canadian Dollars [Member] | Equity Method Investee [Member]
Business Combinations [Line Items]
Revenue, related parties, affiliates							2,900,000		3,100,000
Accounts receivable, related parties, affiliates												1,400,000		0
Pacer [Member] | Canadian Dollars [Member] | Equity Method Investee [Member] | Financial Support [Member]
Business Combinations [Line Items]
Financing commitments, amounts paid							$ 10,200,000		$ 23,000,000
Pacer [Member] | Canadian Dollars [Member] | Equity Method Investee [Member] | Financial Support [Member] | Pacer Equity Method Investee in Receivership [Member]
Business Combinations [Line Items]
Financing commitments, amounts paid						$ 38,300,000
Unconsolidated affiliates, financing commitments, amounts repaid						$ 12,800,000
Pacer [Member] | Canadian Dollars [Member] | Equity Method Investee [Member] | Performance Guarantees [Member]
Business Combinations [Line Items]
Guarantees issued, related parties														$ 61,200,000
Pacer [Member] | Canadian Dollars [Member] | Equity Method Investee [Member] | Other Financial Guarantees [Member]
Business Combinations [Line Items]
Guarantees issued, related parties												$ 0
Pacer [Member] | Canadian Dollars [Member] | Equity Method Investee [Member] | Guarantee of Indebtedness of Others [Member] | Financial Support [Member] | Pacer Equity Method Investee in Receivership [Member] | Revolving Loans [Member]
Business Combinations [Line Items]
Financing commitments, amounts paid		$ 20,800,000

[1] Represent adjustments to preliminary estimates of the fair values of net assets acquired within the measurement period. See Note 3 - Acquisitions for discussion of ASU 2015-16, which was adopted in the fourth quarter of 2015.