Stock-Based Compensation and Other Employee Benefit Plans (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Shares available for grant or issuance	6,226,093	6,226,093		6,226,093
Stock options exercised, intrinsic value		$ 0.2	$ 2.2	$ 6.5	$ 5.7
Stock options exercised, proceeds		0.1	1.5	0.8	3.4
Restricted Stock Plan [Member]
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Unearned compensation	19.9	19.9		19.9
Unearned compensation, weighted average expected recognition period	1 year 3 months 18 days
Vested awards, intrinsic value		$ 0.2	$ 0.4	$ 6.0	$ 1.1
Employee Stock Option Plan [Member]
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Stock-based compensation, percentage vested				100.00%
Employee Stock Purchase Plan [Member]
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Stock-based compensation plan, description				The Company's employee stock purchase plans 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 documents.
Stock-based compensation, purchase price of common stock, percentage of fair value				85.00%
Stock-based compensation, fair value assumptions, method used				The fair value of purchases under the Company's employee stock purchase plans is estimated using the Black-Scholes option-pricing valuation model.