Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Revenue Recognition (Details)

v3.21.1
Summary of Significant Accounting Policies - Revenue Recognition (Details)
$ in Millions
 3 Months Ended
Mar. 31, 2021
USD ($)
pool
Mar. 31, 2020
USD ($)
Dec. 31, 2020
USD ($)
Revenue Recognition [Line Items]      
Revenues recognized related to change orders and claims $ 158.6   $ 141.2
Change in contract estimates, (favorable) unfavorable impact on operating results, percent (11.50%) (7.30%)  
Percent of total revenues recognized associated with revenue recognition method 44.40% 48.10%  
Revenue, related to performance obligation satisfied in previous periods $ 54.3    
Revenue recognized related to amounts in contract liabilities outstanding at the beginning of period $ 245.7    
Number of pools used for the purpose of calculating its historical credit loss experience | pool 1    
Long-term accounts receivable, net $ 13.5   13.4
Current retainage balances 275.9   306.3
Non-current retainage balances 112.3   88.2
Unbilled receivables 561.3   472.3
Accounts Payable and Accrued Expenses      
Revenue Recognition [Line Items]      
Unearned revenues, current portion 41.2   $ 53.6
Domestic Communications Project      
Revenue Recognition [Line Items]      
Change in contract estimates, (favorable) unfavorable impact on operating results, amount 14.8    
Contract value $ 91.8    
Percentage of project completion 56.00%    
Pipeline Transmission Project - Canada - Project One      
Revenue Recognition [Line Items]      
Change in contract estimates, (favorable) unfavorable impact on operating results, amount   $ 11.6  
Contract value $ 114.0    
Percentage of project completion 98.00%