XML 80 R58.htm IDEA: XBRL DOCUMENT v3.24.0.1
Significant accounting policies - Additional Information (Detail)
$ in Thousands
 12 Months Ended
Dec. 31, 2023
USD ($)
facility
Dec. 31, 2022
USD ($)
Significant Accounting Policies [Line Items]    
Number of electric generating facilities | facility 3  
Cost of plant in service $ 552,701 $ 559,630
Accumulated depreciation related to commonly owned facilities 83,283 75,820
Expenditures $ 72,584 110,268
Number of power generating facilities | facility 2  
Generating assets of Long Sault $ 18,373,961 17,627,613
Non-regulated energy sales 2,698,015 2,765,013
Interest expense on long-term debt and others 353,656 278,574
Non-Regulated Energy    
Significant Accounting Policies [Line Items]    
Non-regulated energy sales 296,314 350,797
Long Sault and Saint-Damase Wind Powered Generating Facility | Primary Beneficiary | Power plant    
Significant Accounting Policies [Line Items]    
Generating assets of Long Sault 57,740 57,241
Long-term debt of Long Sault 12,738 15,024
Operating expenses and amortization 5,986 5,834
Interest expense on long-term debt and others 1,384 1,723
Long Sault and Saint-Damase Wind Powered Generating Facility | Primary Beneficiary | Power plant | Non-Regulated Energy    
Significant Accounting Policies [Line Items]    
Non-regulated energy sales $ 17,317 $ 19,752
Minimum    
Significant Accounting Policies [Line Items]    
Ownership interest in commonly owned facilities 7.52%  
Lease renewal term 1 year  
Maximum    
Significant Accounting Policies [Line Items]    
Ownership interest in commonly owned facilities 60.00%  
Lease renewal term 5 years  
Power sales contracts | Minimum    
Significant Accounting Policies [Line Items]    
Intangible asset, useful life 6 years  
Power sales contracts | Maximum    
Significant Accounting Policies [Line Items]    
Intangible asset, useful life 25 years  
Interconnection agreements    
Significant Accounting Policies [Line Items]    
Intangible asset, useful life 40 years  
Customer relationships | Minimum    
Significant Accounting Policies [Line Items]    
Intangible asset, useful life 25 years  
Customer relationships | Maximum    
Significant Accounting Policies [Line Items]    
Intangible asset, useful life 40 years