Commitments and Contingencies (Collective Bargaining Agreements and Multi-Employer Plans) (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended			9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014 Multi-Employer Plans, Pension [Member] Central States Southeast And Southwest Areas Pension Fund [Member]	Nov. 15, 2011 Multi-Employer Plans, Pension [Member] Central States Southeast And Southwest Areas Pension Fund [Member]	Sep. 30, 2014 Multi-Employer Plans, Pension [Member] Withdrawal from Multi-Employer Defined Benefit Plan [Member] Central States Southeast And Southwest Areas Pension Fund [Member]
Loss Contingencies [Line Items]
Multi-employer plans, collective bargaining agreements, description	Certain of MasTec’s subsidiaries are party to various collective bargaining agreements with unions representing certain of their employees. The agreements require the subsidiaries party to the agreements to pay specified wages, provide certain benefits to their union employees and contribute certain amounts to multi-employer pension plans and employee benefit trusts. The collective bargaining agreements expire at various times and have typically been renegotiated and renewed on terms similar to the ones contained in the expiring agreements.
Loss contingency, evaluation of estimated loss				On November 15, 2011, the Company, along with other members of the Pipe Line Contractors Association (“PLCA”), voluntarily withdrew from the Central States Southeast and Southwest Areas Pension Fund (“Central States”), a defined benefit multi-employer pension plan that is in critical status. In connection with this withdrawal, a $6.4 million withdrawal liability was established based on an estimate provided by the Central States administrator of such liability as of the date of withdrawal. The Company began paying installments towards this withdrawal liability in 2013, of which $4.5 million was outstanding as of September 30, 2014. The Company withdrew from Central States in order to mitigate its liability in connection with the plan; however, Central States has asserted that the PLCA members did not effectively withdraw in 2011 and are, therefore, responsible for a withdrawal liability that includes 2011 contribution amounts. By letter dated March 14, 2013, Central States demanded $11 million in withdrawal liability from the Company, which included 2011 contribution amounts. The Company is vigorously opposing this demand because it believes that it legally and effectively withdrew from Central States on November 15, 2011. If Central States were to prevail in its assertion that the Company withdrew after that date, then the initial amount of the Company’s withdrawal liability would increase to approximately $11 million.
Withdrawal liability		$ 4.5	$ 6.4
Maximum loss				$ 11