Contingencies and Regulatory Matters - Textual - So Regulatory Matters MPC (Details) - MISSISSIPPI POWER CO - USD ($) $ in Millions	Feb. 07, 2018	Dec. 31, 2013
Schedule of Regulatory Assets and Liabilities [Line Items]
Annual PEP filing rate increase amount		$ 15
Subsequent Event
Schedule of Regulatory Assets and Liabilities [Line Items]
Annual PEP filing rate increase amount	$ 26
Public utilities, approved return on equity	9.33%
Regulatory equity ratio	55.00%