Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation - RSUs to be Settled in Cash (Details)

v3.21.1
Stock-Based Compensation - RSUs to be Settled in Cash (Details) - Restricted Stock Units to be Settled in Cash
$ in Millions
3 Months Ended
Mar. 31, 2021
USD ($)
unit
shares
Mar. 31, 2020
USD ($)
Dec. 31, 2020
USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of equal annual installments | unit 3    
Amount in cash received for each RSU is equal to the fair value of this number of Quanta common stock shares (in shares) | shares 1    
Compensation expense related to RSUs to be settled in cash $ 4.9 $ 1.1  
Payments to settle liabilities under compensation plan 7.4 $ 3.3  
Accrued liabilities under compensation plan $ 6.2   $ 8.7