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