Acquisitions and Other Investments - 2013 Acquisitions (Narrative) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended			6 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended
	Jun. 30, 2013 Big Country [Member]	May 02, 2013 Big Country [Member]	May 02, 2013 Big Country [Member] Long-term Debt [Member]	Jun. 30, 2013 Big Country [Member] Earn-out Arrangements [Member]	May 02, 2013 Big Country [Member] Earn-out Arrangements [Member]	Jun. 30, 2013 Data Cell [Member]	Apr. 02, 2013 Data Cell [Member]	Jun. 30, 2013 Acquisitions During 2013 [Member]	Jun. 30, 2013 Acquisitions During 2013 [Member]
Business Acquisition [Line Items]
Effective date of acquisition	May 01, 2013					Apr. 01, 2013
Business combination, percentage of voting interests acquired		100.00%					100.00%
Business combination, name of acquired entity	Big Country Energy Services, Inc.					Data Cell Systems, Inc.
Acquisition payments in cash		$ 103.5
Earn-out period					5 years
Estimated fair value of contingent consideration					22.8
Debt assumed			24.4
Business combination, contingent consideration arrangements, basis for amount				The earn-out is equal to 25% of the excess, if any, of Big Country’s annual earnings before interest, taxes, depreciation and amortization, over certain thresholds set forth in the purchase agreement, payable annually in cash.
Business combination, description of acquired entity	Big Country is a North American oil and gas pipeline and facility construction services company, headquartered in Calgary, Alberta, Canada.  Big Country also has construction offices in Alberta, British Columbia and Saskatchewan, as well as in Wyoming and North Dakota. Big Country's services include oil, natural gas and natural gas liquids gathering systems and pipeline construction; pipeline modification and replacement services; compressor and pumping station construction; and other related services supporting the oil and gas production, processing and transportation industries.					Data Cell was formerly a subcontractor to MasTec's wireless business and will provide self-perform communications tower construction, installation, maintenance and other services in support of telecommunications infrastructure construction in the Company's communications segment.
Business combination, goodwill recognized, description	Goodwill arising from the acquisition represents the estimated value of Big Country'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 Big Country and MasTec.
Business combination, goodwill, tax deductible amount		4.1
Fair value measurements, significant assumptions				The fair value of the earn-out obligation 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 combination, contingent consideration arrangements, range of outcomes, value, low					0.3
Business combination, contingent consideration arrangements, range of outcomes, value, high					55.3
Business combination, contingent consideration arrangements, range of outcomes, maximum unlimited				there is no maximum earn-out payment amount.
Acquisition costs								$ 0.9	$ 1.4