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COMMITMENTS AND CONTINGENCIES - ENVIRONMENTAL MATTERS (Details)
T in Millions, $ in Millions
 1 Months Ended 3 Months Ended 63 Months Ended
Apr. 30, 2023
MMBTU
Jan. 31, 2023
micrograms
Dec. 31, 2020
micrograms
performance_obligations
Mar. 31, 2023
USD ($)
micrograms
MW
performance_obligations
generating_units
T
Mar. 31, 2023
USD ($)
performance_obligations
MW
Dec. 31, 2022
USD ($)
Dec. 31, 2021
USD ($)
Manufactured gas plant remediation              
Regulatory assets | $       $ 3,325.3 $ 3,325.3 $ 3,306.9  
Environmental remediation costs              
Manufactured gas plant remediation              
Regulatory assets | $       $ 590.6 $ 590.6 610.7  
Cross State Air Pollution Rule - Good Neighbor Plan | Electric | Maximum              
Air quality              
RICE unit megawatts | MW       25 25    
Mercury and Air Toxics Standards | Electric | Subsequent event              
Air quality              
Current level of particulate matter in pounds per million british thermal unit | MMBTU 0.03            
EPA proposed lower limit for particulate matter | MMBTU 0.01            
Even lower level of particulate matter that the EPA is seeking opinions on | MMBTU 0.006            
National Ambient Air Quality Standards | Electric              
Air quality              
The EPA issued a draft policy assessment in support of revisiting the decision to make no changes to the 2015 Ozone standards | performance_obligations       0 0    
Number of revisions necessary to meet the 2012 standard for particulate matter | performance_obligations     0        
Current number of micrograms per cubic meter that particulate matter needs to be below     12        
Current level of micrograms per cubic meter under 24-hour standard that fine particulate matter needs to be below     35        
Lowest limit that will cause nonattainment       10      
National Ambient Air Quality Standards | Electric | Maximum              
Air quality              
Proposed primary (health-based) annual standard   10          
The EPA is taking comments on this full range of micrograms per cubic meter       11      
New possible number of micrograms per cubic meter that particulate matter may be lowered to       11      
National Ambient Air Quality Standards | Electric | Minimum              
Air quality              
Proposed primary (health-based) annual standard   9          
The EPA is taking comments on this full range of micrograms per cubic meter       8      
New possible number of micrograms per cubic meter that particulate matter may be lowered to       10      
Climate Change | Electric              
Air quality              
Capacity of coal-fired generation retired, in megawatts | MW         1,900    
Capacity of fossil-fueled generation to be retired by the end of 2026, in megawatts | MW       1,500      
Company goal for percentage of carbon emissions reduction below 2005 levels by the end of 2025       60.00%      
Company goal for percentage of carbon emissions reduction below 2005 levels by the end of 2030       80.00%      
Climate Change | Natural gas              
Air quality              
Carbon dioxide emissions | T       29.3      
Clean Water Act Cooling Water Intake Structure Rule | Electric              
Water quality              
Number of generating units that may be retired | generating_units       4      
Steam Electric Effluent Limitation Guidelines | Electric              
Water quality              
Number of new ELG rule requirements that affect our electric utilities | performance_obligations       2      
Capital investment to achieve required discharge limits | $       $ 110.0 $ 110.0    
Steam Electric Effluent Limitation Guidelines | Electric | OCPP Units 7 and 8 | WE              
Water quality              
Capital investment to achieve required discharge limits | $             $ 10.0
Steam Electric Effluent Limitation Guidelines | Electric | Weston 3 | WPS              
Water quality              
Capital investment to achieve required discharge limits | $       10.0 10.0    
Steam Electric Effluent Limitation Guidelines | Electric | Elm Road Generating Station | WE              
Water quality              
Capital investment to achieve required discharge limits | $       90.0 90.0    
Manufactured Gas Plant Remediation | Natural gas              
Manufactured gas plant remediation              
Reserves for future environmental remediation | $       491.7 491.7 499.6  
Manufactured Gas Plant Remediation | Natural gas | Environmental remediation costs              
Manufactured gas plant remediation              
Regulatory assets | $       $ 590.6 $ 590.6 $ 610.7