Acquisitions (2014 Acquisitions) (Narrative) (Details) (USD $)			9 Months Ended		0 Months Ended	3 Months Ended	9 Months Ended						3 Months Ended	9 Months Ended	0 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended	0 Months Ended	9 Months Ended	0 Months Ended	9 Months Ended	0 Months Ended	9 Months Ended	0 Months Ended	9 Months Ended
	Sep. 30, 2014 Performance Guarantees [Member]	Dec. 31, 2013 Performance Guarantees [Member]	Sep. 30, 2014 Earn-Out Arrangements [Member]	Sep. 30, 2013 Earn-Out Arrangements [Member]	Jun. 01, 2014 Pacer [Member]	Sep. 30, 2014 Pacer [Member]	Sep. 30, 2014 Pacer [Member]	Jun. 01, 2014 Pacer [Member]	Sep. 30, 2014 Pacer [Member] Investee [Member] Performance Guarantees [Member]	Sep. 30, 2014 Pacer [Member] Investee [Member] Performance Guarantees [Member] Beneficial Ownership [Member]	Sep. 30, 2014 Pacer [Member] Investee [Member] Other Financial Guarantees [Member]	Sep. 30, 2014 Pacer [Member] Investee [Member] Financing Receivables [Member] Other Current Assets [Member]	Sep. 30, 2014 Pacer [Member] Investee [Member] Related Customer [Member] Infrastructure Construction Services [Member]	Sep. 30, 2014 Pacer [Member] Investee [Member] Related Customer [Member] Infrastructure Construction Services [Member]	Jun. 01, 2014 Pacer [Member] Earn-Out Arrangements [Member]	Sep. 30, 2014 Pacer [Member] Earn-Out Arrangements [Member]	Sep. 30, 2014 Pacer [Member] Current Liabilities [Member]	Sep. 30, 2014 Pacer [Member] Liability [Member] Earn-Out Arrangements [Member]	Jun. 01, 2014 Pacer [Member] Liability [Member] Earn-Out Arrangements [Member]	Sep. 30, 2014 Pacer [Member] Other Non-Current Assets [Member]	Apr. 01, 2014 April 2014 Acquisitions [Member]	Sep. 30, 2014 April 2014 Acquisitions [Member]	Apr. 01, 2014 April 2014 Acquisitions [Member] Earn-Out Arrangements [Member]	Sep. 30, 2014 April 2014 Acquisitions [Member] Liability [Member] Earn-Out Arrangements [Member]	Jan. 01, 2014 January 2014 Acquisitions [Member]	Sep. 30, 2014 January 2014 Acquisitions [Member]	Jan. 01, 2014 January 2014 Acquisitions [Member] Earn-Out Arrangements [Member]	Sep. 30, 2014 January 2014 Acquisitions [Member] Liability [Member] Earn-Out Arrangements [Member]
Business Combinations [Line Items]
Business combinations, effective date							Jun. 01, 2014															Apr. 01, 2014				Jan. 01, 2014
Business combinations, percentage of voting interests acquired						100.00%	100.00%															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.															a telecommunications services firm that specializes in the installation of in-home security systems				a telecommunications services firm that specializes in the engineering, installation, furnishing and integration of telecommunications equipment
Business combination, provisional information, initial accounting incomplete, adjustment, assets																				$ (9,800,000)
Business combinations, provisional information, initial accounting incomplete, adjustment, liabilities																1,400,000	7,800,000
Business combinations, provisional information, initial accounting incomplete, adjustment, intangible assets						2,700,000
Business combinations, provisional information, initial accounting incomplete, adjustment, goodwill						16,600,000
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.
Business combinations, goodwill, expected tax deductible amount								0
Revenue, related parties													2,000,000	3,000,000
Receivables, related parties													2,500,000	2,500,000
Other receivables, due from related parties												14,800,000
Guarantees issued, related parties	748,600,000	1,100,000,000							219,000,000	92,000,000	31,000,000
Business combinations, contingent consideration arrangements, basis for amount																		The contingent consideration included in the table above is equal to 25% of the excess, if any, of Pacer’s 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						5 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 incorporates significant inputs not observable in the market. Key assumptions in the estimated valuation include the discount rate and probability-weighted EBITDA projections.
Business combinations, contingent consideration arrangements, range of outcomes, value, low																			0
Business combinations, contingent consideration arrangements, range of outcomes, value, high																			69,000,000
Business combinations, contingent consideration arrangements, range of outcomes, maximum unlimited																		there is no maximum earn-out payment amount
Business combinations, payments in cash					126,500,000																17,200,000				23,800,000
Fair value of contingent consideration (earn-out liability)			$ 34,988,000	$ 29,971,000											$ 25,700,000								$ 600,000				$ 8,700,000