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CONTINGENCIES, COMMITMENTS, AND GUARANTEES - MPC Litigation (Details) - Purported Violations Of Mississippi Consumer Protection Act - Pending Litigation - Mississippi Power $ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2019 plaintiff | Dec. 31, 2018 USD ($) defendant plaintiff
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Number of plaintiffs | plaintiff | 4 | 10
Loss contingency, number of defendants | defendant |  | 3
Public utilities, underpayment of refunds | $ |  | $ 23.5

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