Supplemental Guarantor Financial Information (Condensed Consolidating Balance Sheets (Unaudited)) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Assets
Total current assets	$ 2,198,696		$ 2,168,989
Property and equipment, net	862,923		747,808
Operating lease assets	233,423		0
Goodwill and other intangible assets, net	1,325,800		1,269,700
Investments in and advances to consolidated affiliates, net	0		0
Other long-term assets	237,798		253,436
Total assets	4,858,652		4,439,953
Liabilities and equity
Total current liabilities	1,334,506		1,283,611
Long-term debt, including finance leases	1,221,127		1,324,223
Long-term operating lease liabilities	159,283		0
Other long-term liabilities	464,400		440,100
Total liabilities	3,179,348		3,047,929
Total equity	1,679,304	$ 1,551,338	1,392,024	$ 1,489,820	$ 1,430,398	$ 1,433,353
Total liabilities and equity	4,858,652		4,439,953
Reportable Legal Entities [Member] | MasTec, Inc. [Member]
Assets
Total current assets	0		0
Property and equipment, net	0		0
Operating lease assets	0
Goodwill and other intangible assets, net	0		0
Investments in and advances to consolidated affiliates, net	1,656,200		1,373,100
Other long-term assets	18,400		16,800
Total assets	1,674,600		1,389,900
Liabilities and equity
Total current liabilities	0		0
Long-term debt, including finance leases	0		0
Long-term operating lease liabilities	0
Other long-term liabilities	0		0
Total liabilities	0		0
Total equity	1,674,600		1,389,900
Total liabilities and equity	1,674,600		1,389,900
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Assets
Total current assets	2,036,800		1,993,000
Property and equipment, net	821,700		699,200
Operating lease assets	216,900
Goodwill and other intangible assets, net	1,244,500		1,188,000
Investments in and advances to consolidated affiliates, net	1,118,900		1,138,400
Other long-term assets	39,200		42,000
Total assets	5,478,000		5,060,600
Liabilities and equity
Total current liabilities	1,319,200		1,185,900
Long-term debt, including finance leases	1,217,600		1,319,400
Long-term operating lease liabilities	146,800
Other long-term liabilities	454,600		429,200
Total liabilities	3,138,200		2,934,500
Total equity	2,339,800		2,126,100
Total liabilities and equity	5,478,000		5,060,600
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Assets
Total current assets	266,500		248,500
Property and equipment, net	41,200		48,600
Operating lease assets	16,500
Goodwill and other intangible assets, net	81,300		81,700
Investments in and advances to consolidated affiliates, net	843,000		816,900
Other long-term assets	180,200		194,600
Total assets	1,428,700		1,390,300
Liabilities and equity
Total current liabilities	119,900		170,200
Long-term debt, including finance leases	3,500		4,900
Long-term operating lease liabilities	12,500
Other long-term liabilities	9,800		10,800
Total liabilities	145,700		185,900
Total equity	1,283,000		1,204,400
Total liabilities and equity	1,428,700		1,390,300
Eliminations [Member]
Assets
Total current assets	(104,600)		(72,500)
Property and equipment, net	0		0
Operating lease assets	0
Goodwill and other intangible assets, net	0		0
Investments in and advances to consolidated affiliates, net	(3,618,100)		(3,328,400)
Other long-term assets	0		0
Total assets	(3,722,700)		(3,400,900)
Liabilities and equity
Total current liabilities	(104,600)		(72,500)
Long-term debt, including finance leases	0		0
Long-term operating lease liabilities	0
Other long-term liabilities	0		0
Total liabilities	(104,600)		(72,500)
Total equity	(3,618,100)		(3,328,400)
Total liabilities and equity	$ (3,722,700)		$ (3,400,900)