Annual report pursuant to Section 13 and 15(d)

Commitments and Contingencies - Narrative (Details)

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Commitments and Contingencies - Narrative (Details)
1 Months Ended 9 Months Ended 12 Months Ended
Feb. 26, 2020
Lawsuit
Jan. 21, 2020
USD ($)
Oct. 31, 2019
Lawsuit
Sep. 30, 2019
Lawsuit
Jun. 30, 2019
Lawsuit
Jun. 30, 2019
Lawsuit
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Guarantor Obligations [Line Items]                  
Workers compensation, deductible             $ 300,000 $ 100,000  
Workers compensation insurance aggregate stop loss             5,400,000 5,400,000.0  
Accrued workers’ compensation and auto claims             2,900,000 4,700,000  
Directors and officers liability deductible per occurrence             1,000,000.0 1,000,000.0  
Directors and officers liability aggregate deductible limit             10,000,000.0 10,000,000.0  
Self insurance, aggregate stop loss per claim basis             200,000    
Self insurance, aggregate stop loss per calendar year             5,800,000    
Self insurance, claims accrued             3,000,000 3,200,000  
Warranty accrual             0 0  
Product warranty expense             0 0 $ 0
Outstanding bid bonds              
Bid Bond | Performance Guarantee                  
Guarantor Obligations [Line Items]                  
Estimated costs to complete projects secured by performance and payment bonds             8,000,000    
Performance And Payment Bond | Performance Guarantee                  
Guarantor Obligations [Line Items]                  
Guarantee             $ 40,400,000 22,300,000  
Puerto Rico Municipalities, Failure To Pay Municipal License And Construction Excise Taxes                  
Guarantor Obligations [Line Items]                  
Number of new claims filed | Lawsuit           4      
Western District Of Oklahoma, Federal Securities Lawsuits                  
Guarantor Obligations [Line Items]                  
Number of new claims filed | Lawsuit       2 3        
Number of claims dismissed | Lawsuit     2            
September 2019 Derivative Lawsuits                  
Guarantor Obligations [Line Items]                  
Number of new claims filed | Lawsuit       4          
District of Delaware, Federal Securities Lawsuits                  
Guarantor Obligations [Line Items]                  
Number of new claims filed | Lawsuit       2          
Outstanding Bid Bond                  
Guarantor Obligations [Line Items]                  
Outstanding bid bonds               $ 3,600,000  
Subsequent Event | Puerto Rico Municipalities, Failure To Pay Municipal License And Construction Excise Taxes                  
Guarantor Obligations [Line Items]                  
Number of new claims filed | Lawsuit 5                
Subsequent Event | Mastec Renewables Puerto Rico, LLC                  
Guarantor Obligations [Line Items]                  
Loss contingency, damages sought   $ 500,000,000