Stock-Based Compensation and Other Employee Benefit Plans (Deferred Compensation Plan) (Narrative) (Details) - Deferred Compensation Plan Highly Compensated Employees [Member] - Other Postretirement Benefit Plan [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Deferred compensation plan, description	MasTec offers a deferred compensation plan to its highly compensated employees. These employees are allowed to contribute a percentage of their pre-tax annual compensation to the deferred compensation plan.
Other Long-Term Assets [Member]
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Deferred compensation plan, assets	$ 6.1	$ 4.4
Other Long-Term Liabilities [Member]
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Deferred compensation plan, liabilities	$ 5.9	$ 4.3