Stock-Based Compensation and Other Employee Benefit Plans (Narrative) (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		0 Months Ended	3 Months Ended		6 Months Ended				3 Months Ended	6 Months Ended			6 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Restricted Stock [Member]	Jun. 30, 2013 Restricted Stock [Member]	Jun. 30, 2012 Restricted Stock [Member]	Jun. 30, 2013 Restricted Stock [Member]	Jun. 30, 2012 Restricted Stock [Member]	Jun. 30, 2013 2013 Incentive Plan [Member] Restricted Stock [Member]	Jun. 30, 2013 2003 Plans [Member] Restricted Stock [Member]	Jun. 30, 2013 EC Source Share Award [Member] Restricted Stock [Member]	Jun. 30, 2013 EC Source Share Award [Member] Restricted Stock [Member]	Jun. 30, 2013 2011 ESPP [Member] Employee Stock Purchase [Member]	Jul. 02, 2011 2011 ESPP [Member] Employee Stock Purchase [Member]	Jun. 30, 2013 2013 Bargaining Units ESPP [Member] Employee Stock Purchase [Member]	Mar. 31, 2013 2013 Bargaining Units ESPP [Member] Employee Stock Purchase [Member]	Jun. 30, 2013 ESPPs [Member] Employee Stock Purchase [Member]	Jun. 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, the 2003 Employee Stock Incentive Plan, as amended (the "2003 Employee Plans"), and the Amended and Restated 2003 Stock Incentive Plan for Non-Employees, as amended (the "2003 Non-Employee Plan, and, together with the 2003 Employee Plan, the "2003 Plans"). As a result of the effectiveness of the 2013 Incentive Plan, no additional awards will be made under the 2003 Plans. As of June 30, 2013, the 2013 Incentive Plan had 4,929,697 shares available for issuance, including 2,629,697 shares that were available for issuance under the 2003 Plans at the time they were terminated.			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”).	The MasTec, Inc. 2011 Employee Stock Purchase Plan (the “2011 ESPP" and, together with the 2013 Bargaining Units ESPP, the "ESPPs"), which became effective on July 1, 2011, also provides for the issuance of up to 1,000,000 shares of MasTec, Inc. common stock for eligible employees, of which 805,278 shares remained available for issuance as of June 30, 2013.		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 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.
Number of shares authorized under plan															1,000,000		1,000,000
Shares available for grant	5,734,975		5,734,975							4,929,697	2,629,697			805,278
Unearned compensation					$ 20.5	$ 20.5		$ 20.5
Unearned compensation, weighted average expected recognition period					2 years
Total intrinsic value of vested awards						0.4	1.9	1.1	2.1
Restricted shares - granted								425,246	175,004			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 June 30, 2013, the Company did not anticipate the occurrence of any such forfeitures.
Options granted in period			0
Intrinsic value of options exercised	2.2		5.7	0.3
Proceeds from stock option exercises	$ 1.5	$ 0.2	$ 3.4	$ 0.3
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.