Supplemental Guarantor Financial Information (Condensed Consolidating Statements of Cash Flows (Unaudited)) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Condensed Unaudited Consolidating Statements of Cash Flows [Line Items]
Net cash provided by (used in) operating activities	$ 203,266	$ (46,807)
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	0	(93,684)
Capital expenditures	(60,594)	(34,396)
Proceeds from sale of property and equipment	8,363	8,654
Payments for other investments	(12,000)	(2,190)
Proceeds from other investments	648	10,413
Other investing activities, net	4,843	0
Net cash used in investing activities	(58,740)	(111,203)
Cash flows from financing activities:
Proceeds from credit facilities	675,935	866,397
Repayments of credit facilities	(671,780)	(670,794)
Repayments of other borrowings, net	0	(6)
Payments of finance lease obligations	(30,856)	(17,239)
Repurchases of common stock	(119,427)	(5,652)
Proceeds from stock-based awards	1,476	1,079
Payments for stock-based awards	(572)	(12)
Net financing activities and advances from (to) consolidated affiliates	0	0
Net cash (used in) provided by financing activities	(145,224)	173,773
Effect of currency translation on cash	934	9
Net increase in cash and cash equivalents	236	15,772
Cash and cash equivalents - beginning of period	71,427	27,422	$ 27,422
Cash and cash equivalents - end of period	71,663	43,194	71,427
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
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
Other investing activities, net	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
Payments of finance lease obligations	0	0
Repurchases of common stock	(119,400)	(5,700)
Proceeds from stock-based awards	1,500	1,100
Payments for stock-based awards	(600)
Net financing activities and advances from (to) consolidated affiliates	118,500	4,600
Net cash (used in) provided by financing activities	0	0
Effect of currency translation on cash	0	0
Net increase in cash and cash equivalents	0	0
Cash and cash equivalents - beginning of period	0	0	0
Cash and cash equivalents - end of period	0	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	189,600	(43,500)
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired		(93,700)
Capital expenditures	(59,300)	(32,900)
Proceeds from sale of property and equipment	7,800	4,800
Payments for other investments	0	(1,400)
Proceeds from other investments	600	10,400
Other investing activities, net	4,800
Net cash used in investing activities	(46,100)	(112,800)
Cash flows from financing activities:
Proceeds from credit facilities	673,000	862,700
Repayments of credit facilities	(668,800)	(667,200)
Payments of finance lease obligations	(30,400)	(16,700)
Repurchases of common stock	0	0
Proceeds from stock-based awards	0	0
Payments for stock-based awards	0
Net financing activities and advances from (to) consolidated affiliates	(119,200)	(27,300)
Net cash (used in) provided by financing activities	(145,400)	151,500
Effect of currency translation on cash	0	0
Net increase in cash and cash equivalents	(1,900)	(4,800)
Cash and cash equivalents - beginning of period	36,400	11,900	11,900
Cash and cash equivalents - end of period	34,500	7,100	36,400
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	13,700	(3,300)
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired		0
Capital expenditures	(1,200)	(1,500)
Proceeds from sale of property and equipment	600	3,900
Payments for other investments	(12,000)	(800)
Proceeds from other investments	0	0
Other investing activities, net	0
Net cash used in investing activities	(12,600)	1,600
Cash flows from financing activities:
Proceeds from credit facilities	3,000	3,700
Repayments of credit facilities	(2,900)	(3,600)
Payments of finance lease obligations	(400)	(500)
Repurchases of common stock	0	0
Proceeds from stock-based awards	0	0
Payments for stock-based awards	0
Net financing activities and advances from (to) consolidated affiliates	600	22,700
Net cash (used in) provided by financing activities	300	22,300
Effect of currency translation on cash	900	0
Net increase in cash and cash equivalents	2,200	20,600
Cash and cash equivalents - beginning of period	35,000	15,600	15,600
Cash and cash equivalents - end of period	37,200	36,200	35,000
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
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
Other investing activities, net	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
Payments of finance lease obligations	0	0
Repurchases of common stock	0	0
Proceeds from stock-based awards	0	0
Payments for stock-based awards	0
Net financing activities and advances from (to) consolidated affiliates	0	0
Net cash (used in) provided by financing activities	0	0
Effect of currency translation on cash	0	0
Net increase in cash and cash equivalents	0	0
Cash and cash equivalents - beginning of period	0	0	0
Cash and cash equivalents - end of period	$ 0	$ 0	$ 0