Supplemental Guarantor Financial Information (Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss) [Line Items]
Revenue	$ 1,709,300	$ 2,016,600	$ 1,939,000	$ 1,518,300	$ 1,917,600	$ 1,977,200	$ 1,617,800	$ 1,396,800	$ 7,183,188	$ 6,909,417	$ 6,606,978
Costs of revenue, excluding depreciation and amortization	1,434,200	1,690,600	1,633,400	1,312,000	1,654,000	1,681,400	1,366,600	1,237,300	6,070,244	5,939,308	5,745,307
Depreciation and amortization									235,482	212,930	188,049
Intangible asset, pre-tax impairment charge									3,300
Goodwill, pre-tax impairment charge					47,700					47,700
General and administrative expenses									299,500	287,278	275,103
Interest expense (income), net									77,026	82,571	61,011
Equity in earnings of unconsolidated affiliates									(27,367)	(23,855)	(21,328)
Other (income) expense, net									14,045	(1,780)	(12,990)
Income before income taxes									510,939	365,303	371,826
(Provision for) benefit from income taxes									(116,843)	(106,072)	(22,942)
Net income (loss) before equity in income (loss) from subsidiaries									394,100	259,200	348,900
Equity in income (losses) from subsidiaries, net of tax									0	0	0
Net income	100,700	130,100	120,200	43,100	31,800	120,500	80,400	26,500	394,096	259,231	348,884
Net income (loss) attributable to non-controlling interests									1,762	(428)	1,671
Net income attributable to MasTec, Inc.	$ 100,900	$ 128,600	$ 119,700	$ 43,100	$ 31,900	$ 120,700	$ 80,500	$ 26,600	392,334	259,659	347,213
Comprehensive income (loss)									378,884	262,449	350,986
Reportable Legal Entities [Member] | MasTec, Inc. [Member]
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss) [Line Items]
Revenue									0	0	0
Costs of revenue, excluding depreciation and amortization									0	0	0
Depreciation and amortization									0	0	0
Intangible asset, pre-tax impairment charge									0
Goodwill, pre-tax impairment charge										0
General and administrative expenses									3,200	3,100	2,300
Interest expense (income), net									0	0	0
Equity in earnings of unconsolidated affiliates									0	0	0
Other (income) expense, net									0	0	0
Income before income taxes									(3,200)	(3,100)	(2,300)
(Provision for) benefit from income taxes									800	900	200
Net income (loss) before equity in income (loss) from subsidiaries									(2,400)	(2,200)	(2,100)
Equity in income (losses) from subsidiaries, net of tax									394,700	261,900	349,300
Net income									392,300	259,700	347,200
Net income (loss) attributable to non-controlling interests									0	0	0
Net income attributable to MasTec, Inc.									392,300	259,700	347,200
Comprehensive income (loss)									379,700	262,900	349,300
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss) [Line Items]
Revenue									6,799,400	6,539,300	6,222,300
Costs of revenue, excluding depreciation and amortization									5,703,400	5,609,400	5,378,600
Depreciation and amortization									214,000	190,500	159,100
Intangible asset, pre-tax impairment charge									0
Goodwill, pre-tax impairment charge										0
General and administrative expenses									279,400	266,400	256,300
Interest expense (income), net									138,400	147,000	123,600
Equity in earnings of unconsolidated affiliates									(0)	0	0
Other (income) expense, net									51,400	2,900	(13,000)
Income before income taxes									412,800	323,100	317,700
(Provision for) benefit from income taxes									(111,500)	(94,200)	(18,100)
Net income (loss) before equity in income (loss) from subsidiaries									301,300	228,900	299,600
Equity in income (losses) from subsidiaries, net of tax									0	0	0
Net income									301,300	228,900	299,600
Net income (loss) attributable to non-controlling interests									0	0	2,400
Net income attributable to MasTec, Inc.									301,300	228,900	297,200
Comprehensive income (loss)									303,300	228,900	299,600
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss) [Line Items]
Revenue									474,700	492,600	457,000
Costs of revenue, excluding depreciation and amortization									457,700	452,400	439,000
Depreciation and amortization									21,500	22,400	28,900
Intangible asset, pre-tax impairment charge									3,300
Goodwill, pre-tax impairment charge										47,700
General and administrative expenses									16,900	17,800	16,500
Interest expense (income), net									(61,400)	(64,400)	(62,600)
Equity in earnings of unconsolidated affiliates									(27,400)	(23,900)	(21,300)
Other (income) expense, net									(37,300)	(4,700)	0
Income before income taxes									101,400	45,300	56,500
(Provision for) benefit from income taxes									(6,100)	(12,800)	(5,000)
Net income (loss) before equity in income (loss) from subsidiaries									95,300	32,500	51,500
Equity in income (losses) from subsidiaries, net of tax									0	0	0
Net income									95,300	32,500	51,500
Net income (loss) attributable to non-controlling interests									1,800	(400)	(700)
Net income attributable to MasTec, Inc.									93,500	32,900	52,200
Comprehensive income (loss)									77,900	35,700	53,600
Eliminations [Member]
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss) [Line Items]
Revenue									(90,900)	(122,500)	(72,300)
Costs of revenue, excluding depreciation and amortization									(90,900)	(122,500)	(72,300)
Depreciation and amortization									0	0	0
Intangible asset, pre-tax impairment charge									0
Goodwill, pre-tax impairment charge										0
General and administrative expenses									0	0	0
Interest expense (income), net									0	0	0
Equity in earnings of unconsolidated affiliates									0	0	0
Other (income) expense, net									0	0	0
Income before income taxes									0	0	0
(Provision for) benefit from income taxes									0	0	0
Net income (loss) before equity in income (loss) from subsidiaries									0	0	0
Equity in income (losses) from subsidiaries, net of tax									(394,700)	(261,900)	(349,300)
Net income									(394,700)	(261,900)	(349,300)
Net income (loss) attributable to non-controlling interests									0	0	0
Net income attributable to MasTec, Inc.									(394,700)	(261,900)	(349,300)
Comprehensive income (loss)									$ (382,100)	$ (265,100)	$ (351,400)