Commitments And Contingencies (Narrative) (Detail) In Millions, unless otherwise specified	3 Months Ended				3 Months Ended			12 Months Ended	3 Months Ended					95839 Months Ended	95842 Months Ended	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 Workers Compensation Policy [Member] USD ($)	Mar. 31, 2013 General Liability Policy [Member] USD ($)	Mar. 31, 2013 Automobile Liability Policy [Member] USD ($)	Mar. 31, 2013 Umbrella Policy [Member] USD ($)	Mar. 31, 2013 Pending Litigation [Member] Sintel [Member] USD ($)	Mar. 31, 2013 Pending Litigation [Member] Sintel [Member] EUR (€)	Dec. 31, 2012 Pending Litigation [Member] Sintel [Member] USD ($)	Mar. 31, 2013 Pending Litigation [Member] City Of Marathon [Member]	Mar. 31, 2013 Guarantee Obligations [Member] Letter of Credit [Member] USD ($)	Dec. 31, 2012 Guarantee Obligations [Member] Letter of Credit [Member] USD ($)	Mar. 31, 2013 Performance Guarantee [Member] USD ($)	Dec. 31, 2012 Performance Guarantee [Member] USD ($)	Dec. 31, 9999 Performance Guarantee [Member] Scenario, Forecast [Member] USD ($)	Dec. 31, 9999 Performance Guarantee [Member] Scenario, Forecast [Member] USD ($)	Mar. 31, 2013 Multiemployer Plans, Pension [Member]	Mar. 31, 2013 Minimum [Member] Pending Litigation [Member] City Of Marathon [Member] USD ($)	Mar. 31, 2013 Central States Southeast And Southwest Areas Pension Fund [Member] Multiemployer Plans, Pension [Member] USD ($)	Mar. 31, 2013 Insurance Claims [Member] USD ($)	Dec. 31, 2012 Insurance Claims [Member] USD ($)	Mar. 31, 2013 Insurance Claims [Member] Workers Compensation, General And Automobile Policies [Member] USD ($)	Dec. 31, 2012 Insurance Claims [Member] Workers Compensation, General And Automobile Policies [Member] USD ($)	Mar. 31, 2013 Insurance Claims [Member] Employee Group Health Claims Policy [Member] USD ($)	Dec. 31, 2012 Insurance Claims [Member] Employee Group Health Claims Policy [Member] USD ($)	Mar. 31, 2013 Insurance Claims [Member] Employee Group Health Claims Policy [Member] Per Employee [Member] USD ($)	Mar. 31, 2013 Insurance Claims [Member] Standby Letters of Credit [Member] USD ($)	Dec. 31, 2012 Insurance Claims [Member] Standby Letters of Credit [Member] USD ($)	Mar. 31, 2013 Insurance Claims [Member] Surety Bond [Member] USD ($)	Dec. 31, 2012 Insurance Claims [Member] Surety Bond [Member] USD ($)	Mar. 31, 2013 Withdrawal from Multiemployer Defined Benefit Plan [Member] Central States Southeast And Southwest Areas Pension Fund [Member] Multiemployer Plans, Pension [Member] USD ($)
Commitment And Contingencies [Line Items]
Legal proceeding, plaintiff						The labor union representing the workers of Sistemas e Instalaciones de Telecomunicacion S.A. (“Sintel”)	The labor union representing the workers of Sistemas e Instalaciones de Telecomunicacion S.A. (“Sintel”)		the Company
Damages sought						$ 385	€ 300										$ 6
Pending or threatened litigation, estimated loss								9.6
Letters of credit, outstanding amount										119.3	120.8															53.2	53.2
Outstanding bonds, amount												1,100.0	1,100.0															9.0	9.0
Estimated cost to complete bonded projects														162.2	284.5
Per claim deductible, insurance policies		1	2	2
Maximum coverage, per claim and aggregate					100
Self insurance reserve																					49.8	48.1	1.1	1.1
Self insurance reserve, noncurrent																					29.7	28.5
Maximum loss																									0.4					10.8
Cash collateral held by insurance carriers																			1.4	2.0
Multiemployer plans, collective bargaining arrangement, 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 multi-employer pension plan contribution rates are determined annually and assessed on a “pay-as-you-go” basis based on union employee payrolls.
Multiemployer plans, collective bargaining arrangement, expiration date, description	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.
Underfunded multi-employer pension plans, funding requirements and penalties, description																The Pension Protection Act requires that underfunded pension plans improve their funding ratios within prescribed intervals based on the level of their underfunding. In addition, if a multi-employer defined benefit plan fails to satisfy certain minimum funding requirements, the Internal Revenue Service may impose on the employers contributing to such plan a nondeductible excise tax of 5% on the amount of the accumulated funding deficiency.
Multi-employer pension plan withdrawal obligation, description																		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 condition. In connection with this withdrawal, the Company recorded a $6.4 million withdrawal liability based on an estimate provided by the Central States administrator of such liability as of the date of withdrawal. The Company withdrew from Central States in order to mitigate its liability in connection with the plan. Central States, however, 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 made a demand on the Company for the sum of $10.8 million in withdrawal liability, which sum 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, in fact, withdrew after that date, then the amount of the Company’s withdrawal liability would increase to approximately $10.8 million. In addition, if Central States were to undergo a mass withdrawal, as defined by ERISA and the Pension Benefit Guaranty Corporation, within the three year period commencing with the beginning of the calendar year during which the Company withdrew from the plan, there could be additional liability.
Multiemployer plans, withdrawal liability																		$ 6.4
Other guarantees, description	In the ordinary course of its business, from time to time, MasTec guarantees the obligations of its subsidiaries, including obligations under certain contracts with customers, certain lease obligations and in some states, obligations in connection with obtaining contractors’ licenses.