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COMMITMENTS AND CONTINGENCIES - ENVIRONMENTAL MATTERS (Details) T in Millions, $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2019 USD ($) generating_units change degreecelsius MW | Dec. 31, 2018 USD ($) T
Manufactured gas plant remediation |  |
Regulatory assets | $ 4,037.1 | $ 3,855.8
Environmental remediation costs |  |
Manufactured gas plant remediation |  |
Regulatory assets | $ 697.6 | $ 687.1
Mercury and Air Toxics Standards |  |
Air quality |  |
Revisions to Mercury and Air Toxics Standards | change | 0 |
Climate Change | Electric |  |
Air quality |  |
Company goal for percentage of carbon dioxide emissions reduction | 40.00% |
Long-term company goal for percentage of carbon dioxide emissions reduction by 2050 | 80.00% |
Capacity of coal generation retired since the beginning of 2018 | MW | 1,800 |
Carbon dioxide emissions | T |  | 26.4
Climate Change | Electric | Maximum |  |
Air quality |  |
Global temperature increases limit | degreecelsius | 2 |
Climate Change | Natural gas |  |
Air quality |  |
Carbon dioxide emissions | T |  | 29.4
Steam Electric Effluent Limitation Guidelines | Electric |  |
Water quality |  |
Number of generating units of OCPP and ERGS | generating_units | 6 |
Expected cost to achieve required emissions reductions | $ 70.0 |
Manufactured Gas Plant Remediation | Natural gas |  |
Manufactured gas plant remediation |  |
Reserves for future remediation | 631.8 | $ 616.4
Manufactured Gas Plant Remediation | Natural gas | Environmental remediation costs |  |
Manufactured gas plant remediation |  |
Regulatory assets | $ 697.6 | $ 687.1

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