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Accounts Receivable - Narrative (Details) - USD ($)
1 Months Ended 3 Months Ended 12 Months Ended
Dec. 31, 2019
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Receivables [Abstract]                  
Unbilled revenues $ 22,200,000 $ 22,200,000       $ 16,100,000 $ 22,200,000 $ 16,100,000  
Concentration Risk [Line Items]                  
Bad debt provision. net of (recoveries)             3,038,000 650,000 $ 1,200,000
Accounts receivable, net 135,997,000 135,997,000       148,324,000 135,997,000 $ 148,324,000  
Renewable Energy Industry Customer | Services                  
Concentration Risk [Line Items]                  
Bad debt provision. net of (recoveries)   0 $ 0 $ (1,000,000.0) $ 5,700,000 $ 700,000      
Allowance for doubtful accounts recovery       $ 1,700,000 200,000        
Texas Customer                  
Concentration Risk [Line Items]                  
Bad debt provision. net of (recoveries)         $ 1,400,000        
Accounts receivable, net 1,400,000 $ 1,400,000         $ 1,400,000    
Claim filed to recover past due receivables $ 1,400,000