Supplemental Guarantor Financial Information (Condensed Unaudited Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Condensed Unaudited Consolidating Statements of Cash Flows [Line Items]
Net cash provided by (used in) operating activities	$ 23,217	$ (100,160)
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	(6,684)	(37,444)
Capital expenditures	(87,997)	(56,853)
Proceeds from sale of property and equipment	13,884	7,369
Payments for other investments	(35,713)	(74,482)
Proceeds from other investments	5,415	12,118
Net cash used in investing activities	(111,095)	(149,292)
Cash flows from financing activities:
Proceeds from credit facilities	1,638,874	1,153,230
Repayments of credit facilities	(1,374,552)	(869,100)
Repayments of other borrowings and capital lease obligations	(53,700)	(41,100)
Payments of acquisition-related contingent consideration	(15,929)	(6,676)
Repurchase of common stock	(128,311)	0
Distributions to non-controlling interests	(559)	(1,280)
Proceeds from stock-based awards, net	1,927	5
Other financing activities	0	(6,240)
Net financing activities and advances from (to) consolidated affiliates	0	0
Net cash provided by financing activities	67,724	228,790
Effect of currency translation on cash	512	125
Net decrease in cash and cash equivalents	(19,642)	(20,537)
Cash and cash equivalents - beginning of period	40,326	38,767
Cash and cash equivalents - end of period	20,684	18,230
Reportable Legal Entities [Member] | MasTec, Inc. [Member]
Condensed Unaudited Consolidating Statements of Cash Flows [Line Items]
Net cash provided by (used in) operating activities	0	0
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	0	0
Capital expenditures	0	0
Proceeds from sale of property and equipment	0	0
Payments for other investments	0	0
Proceeds from other investments	0	0
Net cash used in investing activities	0	0
Cash flows from financing activities:
Proceeds from credit facilities	0	0
Repayments of credit facilities	0	0
Repayments of other borrowings and capital lease obligations	0	0
Payments of acquisition-related contingent consideration	0	0
Repurchase of common stock	(128,300)
Distributions to non-controlling interests	0	0
Proceeds from stock-based awards, net	1,900	0
Other financing activities		0
Net financing activities and advances from (to) consolidated affiliates	126,400	0
Net cash provided by financing activities	0	0
Effect of currency translation on cash	0	0
Net decrease in cash and cash equivalents	0	0
Cash and cash equivalents - beginning of period	0	0
Cash and cash equivalents - end of period	0	0
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Unaudited Consolidating Statements of Cash Flows [Line Items]
Net cash provided by (used in) operating activities	(129,600)	(49,900)
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	(6,700)	(37,400)
Capital expenditures	(85,100)	(55,000)
Proceeds from sale of property and equipment	12,300	6,800
Payments for other investments	(11,200)	(1,200)
Proceeds from other investments	0	0
Net cash used in investing activities	(90,700)	(86,800)
Cash flows from financing activities:
Proceeds from credit facilities	1,623,300	1,141,200
Repayments of credit facilities	(1,357,600)	(850,200)
Repayments of other borrowings and capital lease obligations	(49,900)	(36,400)
Payments of acquisition-related contingent consideration	(15,900)	(6,700)
Repurchase of common stock	0
Distributions to non-controlling interests	(600)	(1,300)
Proceeds from stock-based awards, net	0	0
Other financing activities		(6,200)
Net financing activities and advances from (to) consolidated affiliates	11,800	(120,600)
Net cash provided by financing activities	211,100	119,800
Effect of currency translation on cash	0	0
Net decrease in cash and cash equivalents	(9,200)	(16,900)
Cash and cash equivalents - beginning of period	10,000	28,900
Cash and cash equivalents - end of period	800	12,000
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Unaudited Consolidating Statements of Cash Flows [Line Items]
Net cash provided by (used in) operating activities	152,800	(50,300)
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	0	0
Capital expenditures	(2,900)	(1,900)
Proceeds from sale of property and equipment	1,600	600
Payments for other investments	(24,500)	(73,300)
Proceeds from other investments	5,400	12,100
Net cash used in investing activities	(20,400)	(62,500)
Cash flows from financing activities:
Proceeds from credit facilities	15,600	12,000
Repayments of credit facilities	(17,000)	(18,900)
Repayments of other borrowings and capital lease obligations	(3,800)	(4,700)
Payments of acquisition-related contingent consideration	0	0
Repurchase of common stock	0
Distributions to non-controlling interests	0	0
Proceeds from stock-based awards, net	0	0
Other financing activities		0
Net financing activities and advances from (to) consolidated affiliates	(138,200)	120,600
Net cash provided by financing activities	(143,400)	109,000
Effect of currency translation on cash	500	100
Net decrease in cash and cash equivalents	(10,500)	(3,700)
Cash and cash equivalents - beginning of period	30,300	9,900
Cash and cash equivalents - end of period	19,800	6,200
Eliminations [Member]
Condensed Unaudited Consolidating Statements of Cash Flows [Line Items]
Net cash provided by (used in) operating activities	0	0
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	0	0
Capital expenditures	0	0
Proceeds from sale of property and equipment	0	0
Payments for other investments	0	0
Proceeds from other investments	0	0
Net cash used in investing activities	0	0
Cash flows from financing activities:
Proceeds from credit facilities	0	0
Repayments of credit facilities	0	0
Repayments of other borrowings and capital lease obligations	0	0
Payments of acquisition-related contingent consideration	0	0
Repurchase of common stock	0
Distributions to non-controlling interests	0	0
Proceeds from stock-based awards, net	0	0
Other financing activities		0
Net financing activities and advances from (to) consolidated affiliates	0	0
Net cash provided by financing activities	0	0
Effect of currency translation on cash	0	0
Net decrease in cash and cash equivalents	0	0
Cash and cash equivalents - beginning of period	0	0
Cash and cash equivalents - end of period	$ 0	$ 0