Stock-Based Compensation and Other Employee Benefit Plans (Narrative) (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended		0 Months Ended	3 Months Ended		9 Months Ended					3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Restricted Stock [Member]	Sep. 30, 2013 Restricted Stock [Member]	Sep. 30, 2012 Restricted Stock [Member]	Sep. 30, 2013 Restricted Stock [Member]	Sep. 30, 2012 Restricted Stock [Member]	Sep. 30, 2013 2013 Incentive Plan [Member] Restricted Stock [Member]	Sep. 30, 2013 2013 Bargaining Units ESPP [Member] Employee Stock Purchase [Member]	Sep. 30, 2013 2011 ESPP [Member] Employee Stock Purchase [Member]	Jun. 30, 2013 EC Source Share Award [Member] Restricted Stock [Member]	Sep. 30, 2013 EC Source Share Award [Member] Restricted Stock [Member]	Sep. 30, 2013 ESPPs [Member] Employee Stock Purchase [Member]	Sep. 30, 2013 Investor [Member] EC Source Share Award [Member] Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation plan, description										the MasTec, Inc. 2013 Incentive Plan (the "2013 Incentive Plan"), which became effective in May 2013. As of September 30, 2013, the 2013 Incentive Plan had 4,926,681 shares available for issuance.	In March 2013, the Company authorized the issuance of up to 1,000,000 new shares of MasTec, Inc. common stock to eligible employees under the MasTec, Inc. Bargaining Units Employee Stock Purchase Plan (the "2013 Bargaining Units ESPP"). The 2013 Bargaining Units ESPP became effective on July 1, 2013.	The MasTec, Inc. 2011 Employee Stock Purchase Plan (the “2011 ESPP" and, together with the 2013 Bargaining Units ESPP, the "ESPPs") also provides for the issuance of up to 1,000,000 shares of MasTec, Inc. common stock for eligible employees.			The Company's ESPPs allow qualified employees to purchase MasTec, Inc. common stock at 85% of the fair market value of the common stock at the lower of (i) the date of commencement of the offering period or (ii) the last day of the exercise period, as defined in the plan document. Through June 30, 2013, the offering period was an annual period, composed of four interim exercise periods. Effective July 1, 2013, the offering period became quarterly.	During the second quarter of 2013, the Company entered into an agreement with the previous owners of EC Source to establish an incentive program for its employees and granted 350,000 restricted share awards (the “EC Source Share Award”).
Shares available for grant	6,383,118		6,383,118							4,926,681
Number of shares authorized under plan											1,000,000	1,000,000
Unearned compensation					$ 17.4	$ 17.4		$ 17.4
Unearned compensation, weighted average expected recognition period					1 year 4 months 24 days
Total intrinsic value of vested awards						0.9	0.7	2.0	2.9
Restricted shares - granted								428,262					350,000
Share-based compensation, terms of award																In the event that shares granted under the EC Source Share Award are forfeited prior to vesting, the former owners of EC Source will be re-issued the pro-rata percentage of the former owners' contributed shares to total shares awarded under the EC Source share grant.
Share-based compensation, fair value measurement, significant assumptions														As of September 30, 2013, the Company did not anticipate the occurrence of any such forfeitures.
Intrinsic value of stock options exercised	4.6	0.4	10.4	0.7
Proceeds from stock option exercises	0.4	0.3	3.8	0.6
Share-based compensation, purchase price of common stock, percent of fair value															85.00%
Share-based compensation, fair value assumptions, method used															The fair value of purchases under the Company's ESPP is estimated using the Black-Scholes option-pricing valuation model.
Adjustments related to tax withholding, share based compensation			$ 2.4