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Property, plant and equipment - Additional Information (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Property, Plant, and Equipment Disclosure [Line Items]    
Cost of plant in service $ 557,954 $ 531,191
Accumulated depreciation related to commonly owned facilities 59,857 50,919
Expenditures 143,255 61,827
Contribution received 6,376 4,214
Generation    
Property, Plant, and Equipment Disclosure [Line Items]    
Renewable generation assets related to facilities under capital lease and owned by consolidated VIE 114,868 111,806
Renewable generation assets related to facilities under capital lease and owned by consolidated VIE, accumulated depreciation 46,649 43,444
Depreciation expense 1,716 1,708
Distribution and transmission    
Property, Plant, and Equipment Disclosure [Line Items]    
Renewable generation assets related to facilities under capital lease and owned by consolidated VIE 2,018,039 885,087
Renewable generation assets related to facilities under capital lease and owned by consolidated VIE, accumulated depreciation 72,484 28,779
Regulated Services Group    
Property, Plant, and Equipment Disclosure [Line Items]    
Cost of distribution assets 3,076 3,076
Accumulated depreciation $ 1,665 $ 1,321