Commitments and Contingencies - Other (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended				6 Months Ended														18 Months Ended	24 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Workers Compensation Policy [Member]	Jun. 30, 2013 General Liability Policy [Member]	Jun. 30, 2013 Automobile Liability Policy [Member]	Jun. 30, 2013 Umbrella Policy [Member]	Jun. 30, 2013 Insurance Claims [Member]	Dec. 31, 2012 Insurance Claims [Member]	Jun. 30, 2013 Insurance Claims [Member] Workers Compensation, General And Automobile Policies [Member]	Dec. 31, 2012 Insurance Claims [Member] Workers Compensation, General And Automobile Policies [Member]	Jun. 30, 2013 Insurance Claims [Member] Employee Group Health Claims Policy [Member]	Dec. 31, 2012 Insurance Claims [Member] Employee Group Health Claims Policy [Member]	Jun. 30, 2013 Insurance Claims [Member] Employee Group Health Claims Policy [Member] Per Employee [Member]	Jun. 30, 2013 Standby Letters of Credit [Member] Insurance Claims [Member]	Dec. 31, 2012 Standby Letters of Credit [Member] Insurance Claims [Member]	Jun. 30, 2013 Guarantee Obligations [Member] Letter of Credit [Member]	Dec. 31, 2012 Guarantee Obligations [Member] Letter of Credit [Member]	Jun. 30, 2013 Performance Guarantee [Member]	Dec. 31, 2012 Performance Guarantee [Member]	Dec. 31, 2014 Performance Guarantee [Member] Scenario, Forecast [Member]	Dec. 31, 2014 Performance Guarantee [Member] Scenario, Forecast [Member]	Jun. 30, 2013 Surety Bond [Member] Insurance Claims [Member]	Dec. 31, 2012 Surety Bond [Member] Insurance Claims [Member]
Commitments and Contingencies [Line Items]
Letters of credit, outstanding amount													$ 53.2	$ 53.2	$ 119.6	$ 120.8
Outstanding bonds, amount																	1,400.0	1,100.0			10.9	9.0
Estimated cost to complete bonded projects																			655.9	284.5
Per claim deductible, insurance policies		1	2	2
Maximum coverage, per claim and aggregate					100
Self insurance reserve								50.2	48.1	1.2	1.1
Self insurance reserve, noncurrent								29.7	28.5
Maximum loss												0.4
Cash collateral held by insurance carriers						$ 1.4	$ 2.0
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.