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Business, Basis of Presentation and Significant Accounting Policies (Revenue Recognition) (Narrative) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Revenue [Line Items]      
Revenue recognition, performance obligations satisfied in previous periods, revenue recognized (in dollars) $ 13.5 $ 58.3 $ 38.5
Contract with customer, unapproved change orders and/or claims, amount (in dollars) $ 51.0 $ 27.0  
Maximum [Member]      
Revenue [Line Items]      
Revenue recognition, changes in contract estimates, cost-to-cost method, financial effect, percentage 5.00% 5.00% 5.00%
Change order or claim approval process, term within which expected to be completed (in years) 1 year    
Revenue Benchmark [Member] | Concentration Risk from Type of Arrangement [Member] | Master Service and Other Service Agreements [Member]      
Revenue [Line Items]      
Concentration risk, percentage of total 36.00% 36.00% 35.00%
Revenue Benchmark [Member] | Concentration Risk from Type of Arrangement [Member] | Master Service and Other Service Agreements [Member] | Point in Time [Member]      
Revenue [Line Items]      
Concentration risk, percentage of total 5.00% 5.00% 7.00%
Mobilization Costs [Member]      
Revenue [Line Items]      
Capitalized mobilization costs, net $ 5.5