Commitments and Contingencies - Other (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended			0 Months Ended															0 Months Ended
	Sep. 30, 2013	Sep. 30, 2013 Uninsured Risk [Member] Other Noncurrent Assets [Member]	Dec. 31, 2012 Uninsured Risk [Member] Other Noncurrent Assets [Member]	Sep. 30, 2013 Uninsured Risk [Member] Workers Compensation Policy [Member]	Sep. 30, 2013 Uninsured Risk [Member] General Liability Policy [Member]	Sep. 30, 2013 Uninsured Risk [Member] Automobile Liability Policy [Member]	Sep. 30, 2013 Uninsured Risk [Member] Umbrella Policy [Member]	Sep. 30, 2013 Uninsured Risk [Member] Workers Compensation, General And Automobile Policies [Member]	Dec. 31, 2012 Uninsured Risk [Member] Workers Compensation, General And Automobile Policies [Member]	Sep. 30, 2013 Uninsured Risk [Member] Employee Group Health Claims Policy [Member]	Dec. 31, 2012 Uninsured Risk [Member] Employee Group Health Claims Policy [Member]	Sep. 30, 2013 Uninsured Risk [Member] Employee Group Health Claims Policy [Member] Per Employee [Member]	Sep. 30, 2013 Standby Letters of Credit [Member] Uninsured Risk [Member]	Dec. 31, 2012 Standby Letters of Credit [Member] Uninsured Risk [Member]	Sep. 30, 2013 Guarantee Obligations [Member] Letter of Credit [Member]	Dec. 31, 2012 Guarantee Obligations [Member] Letter of Credit [Member]	Sep. 30, 2013 Performance Guarantee [Member]	Dec. 31, 2012 Performance Guarantee [Member]	Sep. 30, 2013 Performance Guarantee [Member] Estimate [Member]	Dec. 31, 2012 Performance Guarantee [Member] Estimate [Member]	Sep. 30, 2013 Surety Bond [Member] Uninsured Risk [Member]	Dec. 31, 2012 Surety Bond [Member] Uninsured Risk [Member]
Commitments and Contingencies [Line Items]
Letters of credit, outstanding amount													$ 52.2	$ 53.2	$ 138.5	$ 120.8
Outstanding bonds, amount																	1,400.0	1,100.0			10.9	9.0
Estimated cost to complete bonded projects																			383.8	284.5
Per claim deductible, insurance policies				1	2	2
Maximum coverage, per claim and aggregate							100
Self insurance reserve								53.1	48.1	1.0	1.1
Self insurance reserve, noncurrent								32.6	28.5
Maximum loss												0.4
Cash collateral held by insurance carriers		$ 1.5	$ 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.