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COMMITMENTS AND CONTINGENCIES - ENVIRONMENTAL MATTERS (Details) $ in Millions | 1 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | ---
Dec. 31, 2024 USD ($) performance_obligations | Nov. 30, 2024 performance_obligations | May 31, 2024 MMBTU performance_obligations | Feb. 29, 2024 micrograms | Aug. 31, 2023 | Dec. 31, 2020 micrograms | Sep. 30, 2025 USD ($) performance_obligations MW | Jun. 30, 2025 performance_obligations | Mar. 31, 2025 numberOfActions
Environmental matters |  |  |  |  |  |  |  |  |
Number of federal deregulatory actions that the EPA announced it will take | numberOfActions |  |  |  |  |  |  |  |  | 31
Manufactured gas plant remediation |  |  |  |  |  |  |  |  |
Regulatory assets | $ | $ 3,378.7 |  |  |  |  |  | $ 3,241.0 |  |
Environmental remediation costs |  |  |  |  |  |  |  |  |
Manufactured gas plant remediation |  |  |  |  |  |  |  |  |
Regulatory assets | $ | $ 570.1 |  |  |  |  |  | $ 522.7 |  |
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 limit of particulate matter, in pounds per million british thermal unit | MMBTU |  |  | 0.03 |  |  |  |  |  |
New limit for particulate matter published in the EPA's 2024 Final Action, in pounds per million british thermal unit | MMBTU |  |  | 0.01 |  |  |  |  |  |
National Ambient Air Quality Standards | Electric |  |  |  |  |  |  |  |  |
Air quality |  |  |  |  |  |  |  |  |
Number of volumes of the Integrated Review Plan the EPA released | 2 |  |  |  |  |  |  |  |
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 |  |  |  |  |  |  | 0 |  |
Percent capacity factor that if combined cycle natural gas plants are above, it causes the rule to be dependent upon the implementation of carbon capture |  |  |  |  |  |  | 40.00% |  |
Number of applicable GHG limits for new simple cycle natural gas-fired combustion turbines |  |  |  |  |  |  | 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% |  |
Number of proposed rule packages the EPA is releasing to address NOx emissions from existing combustion turbines |  | 3 |  |  |  |  |  |  |
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% |  |  |  |  |  |  |
Number of potential regulatory paths the EPA is co-proposing |  |  |  |  |  |  |  | 2 |
Capacity of fossil-fueled generation retired, in megawatts | MW |  |  |  |  |  |  | 2,500 |  |
Capacity of coal-fired generation to be retired by the end of 2031, in megawatts | MW |  |  |  |  |  |  | 900 |  |
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 |  |  | 3 |  |  |  |  |  |
Compliance costs 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 |  |  | 1 |  |  |  |  |  |
Number of new coal categories that were created as part of the 2024 supplemental ELG rule requirements |  |  | 1 |  |  |  |  |  |
Manufactured Gas Plant Remediation | Natural gas |  |  |  |  |  |  |  |  |
Manufactured gas plant remediation |  |  |  |  |  |  |  |  |
Reserves for future environmental remediation | $ | $ 445.8 |  |  |  |  |  | 438.2 |  |
Manufactured Gas Plant Remediation | Natural gas | Environmental remediation costs |  |  |  |  |  |  |  |  |
Manufactured gas plant remediation |  |  |  |  |  |  |  |  |
Regulatory assets | $ | $ 570.1 |  |  |  |  |  | $ 522.7 |  |

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