CONTINGENCIES, COMMITMENTS, AND GUARANTEES - SO Litigation (Details) - Kemper County energy facility assets, net - Mississippi Power - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2016	Dec. 31, 2010
Loss Contingencies [Line Items]
Government grants expected		$ 137	$ 270
Government grants received	$ 387