Acquisitions And Other Investments - 2012 Acquisitions (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended		3 Months Ended	6 Months Ended			6 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended
	Jun. 30, 2013 Data Cell [Member]	Apr. 02, 2013 Data Cell [Member]	Jun. 30, 2013 Bottom Line Services [Member]	Jun. 30, 2013 Bottom Line Services [Member]	Dec. 02, 2012 Bottom Line Services [Member]	Dec. 02, 2012 Bottom Line Services [Member] Earn-out Arrangements [Member]	Jun. 30, 2013 Go Green [Member]	Dec. 02, 2012 Go Green [Member]	Jun. 30, 2013 Dynamic Tower [Member]	Dec. 02, 2012 Dynamic Tower [Member]	Jun. 30, 2012 Acquisitions During 2012 [Member]	Jun. 30, 2012 Acquisitions During 2012 [Member]	Jun. 30, 2013 Accrued Liabilities [Member] Bottom Line Services [Member]	Jun. 30, 2013 Accounts Receivable [Member] Bottom Line Services [Member]
Business Acquisition [Line Items]
Effective date of acquisition	Apr. 01, 2013			Dec. 01, 2012			Dec. 01, 2012		Dec. 01, 2012
Business combination, percentage of voting interests acquired		100.00%			100.00%			100.00%		100.00%
Business combination, name of acquired entity	Data Cell Systems, Inc.			Bottom Line Services, LLC			Go Green Services, LLC		Dynamic Tower Services, Inc.
Acquisition payments in cash					$ 67.6
Earn-out period						5 years
Estimated fair value of contingent consideration						11.1
Business combination, description of acquired entity	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.			BLS is engaged in providing natural gas and petroleum pipeline infrastructure services, primarily in eastern Texas.  Its services include pipeline and facilities construction, painting and maintenance services.			Go Green was formerly a subcontractor to MasTec's oil and gas business and provides self-perform clearing and trenching services for natural gas and petroleum pipeline infrastructure construction in the Company's oil and gas segment.		DTS was formerly a subcontractor to MasTec's wireless business and provides self-perform communications tower construction, installation, maintenance and other services in support of telecommunications infrastructure construction in the Company's communications segment.
Business combination, provisional information, initial accounting incomplete, nature of adjustments				$2.3 million of additional pre-acquisition project cost liabilities were recorded as a result of the ongoing review of the acquired net working capital of BLS. In addition, accounts receivable were reduced by $0.1 million. These adjustments resulted in an increase to the previously recorded amount of BLS goodwill of $2.4 million.					recorded $4.7 million of post-closing purchase price adjustments relating to the 2012 acquisition of DTS during the first quarter of 2013 based on DTS's final closing tangible net worth and net working capital
Business combination, provisional information, initial accounting incomplete, adjustment, financial liabilities													2.3
Business combination, provisional information, initial accounting incomplete, adjustment, financial assets														(0.1)
Goodwill, purchase price allocation adjustment			2.4
Acquisition costs											$ 0	$ 0