Earnings Per Share (Narrative) (Detail) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended	3 Months Ended		9 Months Ended				3 Months Ended		3 Months Ended	9 Months Ended			3 Months Ended		3 Months Ended	9 Months Ended			3 Months Ended		9 Months Ended
	Jul. 31, 2012	Jun. 30, 2012	Dec. 31, 2011	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Restricted Stock [Member]	Sep. 30, 2011 Restricted Stock [Member]	Sep. 30, 2012 Restricted Stock [Member]	Sep. 30, 2011 Restricted Stock [Member]	Sep. 30, 2012 Convertible Debt [Member]	Sep. 30, 2011 Convertible Debt [Member]	Mar. 31, 2011 Convertible Debt [Member] Original 4.0% Notes [Member]	Sep. 30, 2012 Convertible Debt [Member] Original 4.0% Notes [Member]	Sep. 30, 2012 Convertible Debt [Member] New 4.0% Notes [Member]	Sep. 30, 2012 Convertible Debt [Member] New 4.0% Notes [Member]	Sep. 30, 2011 Convertible Debt [Member] New 4.0% Notes [Member]	Mar. 31, 2011 Convertible Debt [Member] New 4.0% Notes [Member]	Mar. 31, 2011 Convertible Debt [Member] Original 4.25% Notes [Member]	Sep. 30, 2012 Convertible Debt [Member] Original 4.25% Notes [Member]	Sep. 30, 2012 Convertible Debt [Member] New 4.25% Notes [Member]	Sep. 30, 2012 Convertible Debt [Member] New 4.25% Notes [Member]	Sep. 30, 2011 Convertible Debt [Member] New 4.25% Notes [Member]	Mar. 31, 2011 Convertible Debt [Member] New 4.25% Notes [Member]	Sep. 30, 2012 Convertible Debt [Member] Total New Senior Convertible Notes [Member]	Sep. 30, 2011 Convertible Debt [Member] Total New Senior Convertible Notes [Member]	Sep. 30, 2012 Convertible Debt [Member] Total New Senior Convertible Notes [Member]	Sep. 30, 2011 Convertible Debt [Member] Total New Senior Convertible Notes [Member]
Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents, shares						0	7,609	0	2,564
Stock repurchase program, amount authorized			$ 150,000,000
Treasury stock acquired, shares	2,000,000	2,900,000			4,600,000
Treasury stock acquired, value	31,200,000	43,800,000			75,000,000
Debt instrument, exchanged amount										$ 0	$ 202,322,000	$ 105,300,000						$ 97,000,000
Debt instrument interest rate, stated percentage												4.00%	4.00%	4.00%	4.00%		4.00%	4.25%	4.25%	4.25%	4.25%		4.25%
Debt instrument, convertible, conversion price per share														$ 15.76	$ 15.76	$ 15.76				$ 15.48	$ 15.48	$ 15.48
Debt instrument, convertible, number of conversion shares, principal amount														6,683,000	6,683,000					6,268,000	6,268,000			13,000,000	13,000,000	13,000,000	13,000,000
Computation of earnings per share, methodology				Basic earnings per share is computed by dividing earnings available to MasTec’s common shareholders by the weighted average number of common shares outstanding for the period. Diluted earnings per share is computed by dividing earnings by the number of fully diluted shares, which includes the effect of potentially dilutive issuances of common shares, as determined using earnings from continuing operations. Potentially dilutive common shares include outstanding stock options and unvested restricted share awards, as calculated under the treasury stock method, as well as shares associated with the Company’s outstanding convertible securities.