Acquisitions - 2012 Acquisitions (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	0 Months Ended	9 Months Ended
	Dec. 01, 2012	Sep. 30, 2013	Dec. 02, 2012
Bottom Line Services [Member]
Business Acquisition [Line Items]
Effective date of acquisition		Dec. 01, 2012
Business combination, name of acquired entity		Bottom Line Services, LLC
Business combination, percentage of voting interests acquired			100.00%
Acquisition payments in cash	$ 67.6
Business combination, description of acquired entity		BLS's services include pipeline and facilities construction, painting and maintenance services, primarily in eastern Texas.
Bottom Line Services [Member] | Earn-out Arrangements [Member]
Business Acquisition [Line Items]
Earn-out period			5 years
Fair value of contingent consideration (earn-out liability)	$ 11.1
Other 2012 Acquisitions [Member]
Business Acquisition [Line Items]
Effective date of acquisition		Dec. 01, 2012
Business combination, description of acquired entity		MasTec acquired a former subcontractor to MasTec's oil and gas business, which provides self-perform clearing and trenching services for natural gas and petroleum pipeline infrastructure construction, and also acquired a former subcontractor to MasTec's wireless business, which provides self-perform communications tower construction, installation, maintenance and other services in support of telecommunications infrastructure construction.