Annual report pursuant to Section 13 and 15(d)

Revenue from Contracts with Customers - Additional Information (Details)

v3.20.4
Revenue from Contracts with Customers - Additional Information (Details) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]      
Percentage of revenue recognized over time (percent) 94.00% 92.00% 93.00%
Contract with customer, asset, revenue recognized $ 644,583,000 $ 496,733,000  
Contract with customer, asset, reclassified to receivable 618,839,000 387,815,000  
Revenue recognized 132,622,000 113,357,000  
Contract with customer, liability, billings 140,275,000 117,577,000  
Revenue, remaining performance obligation $ 2,026,770,000    
Contract term 25 years    
Capitalized commission costs $ 1,735,000 1,735,000  
Capitalized contract cost, project development costs 12,790,000 35,172,000 $ 15,672,000
Impairment charges in connection with the company's commission costs or project development costs $ 0 0  
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01      
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]      
Revenue, remaining performance obligation 33.00%    
Revenue, remaining performance obligation, remaining satisfaction 12 months    
Other liabilities      
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]      
Deferred grant income $ 6,631,000 $ 5,560,000