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Business, Basis of Presentation and Significant Accounting Policies (Narrative) (Details)
$ in Thousands
3 Months Ended
Mar. 31, 2019
USD ($)
segment
Mar. 31, 2018
USD ($)
Dec. 31, 2018
USD ($)
Segment Reporting, Disclosure of Entity's Reportable Segments [Abstract]      
Number of reportable segments | segment 5    
Revenue [Line Items]      
Revenue recognition, performance obligations satisfied in previous periods, revenue recognized (in dollars) $ 12,500 $ 44,300  
Contract with customer, unapproved change orders and/or claims, amount (in dollars) 38,000   $ 56,000
Leases, Operating [Abstract]      
Operating lease assets 223,106   $ 0
Operating leases, liabilities $ 227,200    
Maximum [Member]      
Revenue [Line Items]      
Revenue recognition, changes In contract estimates, cost-to-cost method, financial effect, percentage 5.00% 5.00%  
Change order or claim approval process, term within which expected to be completed (in years) 1 year    
Maximum [Member] | Plan [Member]      
Revenue [Line Items]      
Revenue recognition, performance obligations, completion period (in years) 1 year    
Revenue [Member] | Concentration Risk from Type of Arrangement [Member] | Master Service and Other Service Agreements [Member]      
Revenue [Line Items]      
Concentration risk, percentage of total 41.00% 41.00%  
Revenue [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 6.00% 9.00%