Contingencies - General Litigation Matters (Details) - Pending Litigation $ in Millions	1 Months Ended	12 Months Ended
	Mar. 31, 2019 plaintiff	Dec. 31, 2018 USD ($) defendant plaintiff	Dec. 31, 2017 claim
Shareholder Derivative Lawsuits
Loss Contingencies [Line Items]
Pending number of claims | claim			2
Stay period		30 days
MISSISSIPPI POWER CO | Purported Violations of Mississippi Consumer Protection Act
Loss Contingencies [Line Items]
Number of plaintiffs | plaintiff	4	10
Number of defendants | defendant		3
Underpayment of refunds | $		$ 23.5