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COMMITMENTS AND CONTINGENCIES - ENVIRONMENTAL MATTERS (Details)
$ in Millions
 1 Months Ended 3 Months Ended
May 31, 2024
MMBTU
performance_obligations
Feb. 29, 2024
micrograms
Aug. 31, 2023
Dec. 31, 2020
micrograms
Mar. 31, 2025
USD ($)
numberOfActions
MW
Dec. 31, 2024
USD ($)
Nov. 30, 2024
Dec. 31, 2023
USD ($)
Environmental matters                
Number of federal deregulatory actions that the EPA announced it will take | numberOfActions         31      
Manufactured gas plant remediation                
Regulatory assets | $         $ 3,367.8 $ 3,378.7    
Environmental remediation costs                
Manufactured gas plant remediation                
Regulatory assets | $         $ 540.7 570.1    
Cross State Air Pollution Rule - Good Neighbor Rule | Electric | Maximum                
Air quality                
RICE Unit megawatts | MW         25      
Mercury and Air Toxics Standards | Electric                
Air quality                
Previous level of particulate matter in pounds per million british thermal unit | MMBTU 0.03              
New limit for particulate matter published in the EPA's final rule | MMBTU 0.01              
National Ambient Air Quality Standards | Electric                
Air quality                
Current level of micrograms per cubic meter that particulate matter needs to be below | micrograms       12        
Current level of micrograms per cubic meter under 24-hour standard that particulate matter needs to be below | micrograms       35        
National Ambient Air Quality Standards | Electric | Maximum                
Air quality                
Period of time for EPA review of ozone plan     5 years          
New primary annual PM2.5 level | micrograms   9            
National Ambient Air Quality Standards | Electric | Minimum                
Air quality                
Period of time for EPA review of ozone plan     3 years          
Number of years between evaluation of attainment status     3 years          
Climate Change | Electric                
Air quality                
Number of applicable GHG performance standards for coal plants | performance_obligations 0              
Percent capacity factor that if combined cycle natural gas plants are above it causes the rule to be highly dependent on carbon capture 40.00%              
Number of applicable GHG limits for new simple cycle natural gas-fired combustion turbines | performance_obligations 0              
Percent capacity factor for simple cycle natural gas fired combustion turbines that there are no applicable limits if the capacity factor is less than this. 20.00%              
Percent capacity factor for turbines that will require more stringent NOX limits             20.00%  
Percent capacity factor for turbines that below this percentage will have less restrictive standards             20.00%  
Capacity of coal-fired generation retired, in megawatts | MW         2,500      
Capacity of fossil-fueled generation to be retired by the end of 2031, in megawatts | MW         1,200      
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 | Electric | Maximum                
Air quality                
RICE Unit megawatts | MW         25      
Steam Electric Effluent Limitation Guidelines | Electric                
Water quality                
Number of new ELG rule requirements that affect our electric utilities | performance_obligations 3              
Compliance costs through 2023 associated with the ELG rule that were required to achieve discharge limits | $               $ 105.0
Number of existing coal categories that were kept as part of the 2024 supplemental ELG rule requirements | performance_obligations 1              
Number of new categories that were created as part of the 2024 supplemental ELG rule requirements | performance_obligations 1              
Manufactured Gas Plant Remediation | Natural gas                
Manufactured gas plant remediation                
Reserves for future environmental remediation | $         $ 442.1 445.8    
Manufactured Gas Plant Remediation | Natural gas | Environmental remediation costs                
Manufactured gas plant remediation                
Regulatory assets | $         $ 540.7 $ 570.1