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COMMITMENTS AND CONTINGENCIES - ENVIRONMENTAL MATTERS (Details) $ in Millions | 1 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Oct. 31, 2014 compliance_option | Jun. 30, 2018 USD ($) degreecelsius MW | Dec. 31, 2017 USD ($)
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 expected to be retired by 2020 | MW |  | 1,800 |
Climate Change | Electric | Maximum |  |  |
Air quality |  |  |
Global temperature increases limit | degreecelsius |  | 2 |
Clean Water Act Cooling Water Intake Structure Rule | Electric |  |  |
Water quality |  |  |
Number of compliance options available to meet standard | compliance_option | 7 |  |
Renewal period for facility permits |  | 5 years |
Steam Electric Effluent Limitation Guidelines | Electric |  |  |
Water quality |  |  |
Renewal period for facility permits |  | 5 years |
Expected cost to achieve required emissions reductions |  | $ 70.0 |
Manufactured Gas Plant Remediation | Natural gas |  |  |
Manufactured gas plant remediation |  |  |
Regulatory assets recorded for remediation of manufactured gas plant sites |  | 669.9 | $ 676.6
Reserves recorded for remediation of manufactured gas plant sites |  | $ 617.2 | $ 617.2

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