XML 100 R73.htm IDEA: XBRL DOCUMENT v3.22.0.1
Regulatory assets (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2021
Feb. 28, 2021
Dec. 31, 2020
Regulatory Assets [Line Items]      
Current regulatory assets $ 118,691   $ 68,527
Regulatory assets 357,851   379,381
Total regulatory assets 476,542   447,908
Regulatory assets not earning a rate of return 296,600   332,500
Natural gas costs recoverable through rate adjustments      
Regulatory Assets [Line Items]      
Current regulatory assets 86,371   42,481
Regulatory assets $ 5,186   21,539
Total regulatory assets   $ 44,000  
Natural gas costs recoverable through rate adjustments | Minimum      
Regulatory Assets [Line Items]      
Regulatory asset, recovery period Up to 1 year    
Natural gas costs recoverable through rate adjustments | Maximum      
Regulatory Assets [Line Items]      
Regulatory asset, recovery period Up to 2 years    
Decoupling      
Regulatory Assets [Line Items]      
Regulatory asset, recovery period Up to 1 year    
Current regulatory assets $ 9,131   703
Conservation programs      
Regulatory Assets [Line Items]      
Regulatory asset, recovery period Up to 1 year    
Current regulatory assets $ 8,225   7,117
Cost recovery mechanisms      
Regulatory Assets [Line Items]      
Current regulatory assets 4,536   10,645
Regulatory assets $ 44,870   16,245
Cost recovery mechanisms | Minimum      
Regulatory Assets [Line Items]      
Regulatory asset, recovery period Up to 1 year    
Cost recovery mechanisms | Maximum      
Regulatory Assets [Line Items]      
Regulatory asset, recovery period Up to 10 years    
Other regulatory assets      
Regulatory Assets [Line Items]      
Current regulatory assets $ 10,428   7,581
Regulatory assets $ 9,742   6,356
Other regulatory assets | Minimum      
Regulatory Assets [Line Items]      
Regulatory asset, recovery period Up to 1 year    
Other regulatory assets | Maximum      
Regulatory Assets [Line Items]      
Regulatory asset, recovery period Up to 17 years    
Pension and postretirement benefits      
Regulatory Assets [Line Items]      
Regulatory asset, recovery period **    
Regulatory assets $ 142,681   155,942
Plant costs/asset retirement obligation costs      
Regulatory Assets [Line Items]      
Regulatory asset, recovery period Over plant lives    
Regulatory assets $ 63,116   71,740
Plants to be retired      
Regulatory Assets [Line Items]      
Regulatory asset, recovery period -    
Regulatory assets $ 50,070   65,919
Manufactured gas plant sites remediation      
Regulatory Assets [Line Items]      
Regulatory asset, recovery period -    
Regulatory assets $ 26,053   26,429
Taxes recoverable from customers      
Regulatory Assets [Line Items]      
Regulatory asset, recovery period Over plant lives    
Regulatory assets $ 12,339   10,785
Long-term debt refinancing costs      
Regulatory Assets [Line Items]      
Regulatory asset, recovery period Up to 39 years    
Regulatory assets $ 3,794   $ 4,426