Annual report pursuant to Section 13 and 15(d)

Revenue from Contracts with Customers - Additional Information (Details)

v3.19.3.a.u2
Revenue from Contracts with Customers - Additional Information (Details) - USD ($)
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Jan. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]      
Percentage of revenue recognized over tIme (percent) 92.00% 93.00%  
Deferred grant income $ 6,885,000 $ 6,637,000  
Contract with customer, asset, revenue recognized 535,021,000 485,143,000  
Contract with customer, asset, reclassified to receivable 431,717,000 510,470,000  
Revenue recognized 75,070,000 95,318,000  
Contract with customer, liability, billings $ 73,675,000 80,007,000  
Contract term 25 years    
Capitalized commission costs $ 1,735,000 927,000  
Capitalized contract cost, project development costs 35,172,000 15,672,000  
Impairment charges in connection with the the company's commission costs or project development costs $ 0 0  
Minimum      
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]      
Contract receivable retainage percentage 5.00%    
Maximum      
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]      
Contract receivable retainage percentage 10.00%    
ASU 2014-09      
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]      
Decrease in retained earnings     $ 4,454,000
Other liabilities      
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]      
Deferred grant income $ 5,560,000 $ 6,342,000