CONTINGENCIES, COMMITMENTS, AND GUARANTEES - MPC Litigation (Details) $ in Millions					1 Months Ended
	Sep. 27, 2019 USD ($)	Mar. 14, 2019 plaintiff	Nov. 21, 2018 plaintiff	May 18, 2018 USD ($)	Nov. 30, 2018 USD ($) defendant	May 31, 2018 agreement
Schedule of Regulatory Assets and Liabilities [Line Items]
Number of plaintiffs | plaintiff			10
Martin Product Sales, LLC Litigation
Schedule of Regulatory Assets and Liabilities [Line Items]
Loss contingency, damages sought, value				$ 143.0
Purported Violations Of Mississippi Consumer Protection Act | Pending Litigation | Mississippi Power
Schedule of Regulatory Assets and Liabilities [Line Items]
Loss contingency, number of agreements | agreement						2
Number of plaintiffs | plaintiff		4
Loss contingency, number of defendants | defendant					3
Public utilities, underpayment of refunds					$ 23.5
Martin Product Sales, LLC Litigation | Martin Product Sales, LLC Litigation
Schedule of Regulatory Assets and Liabilities [Line Items]
Loss contingency, damages sought, value	$ 50.0
Loss contingency, damages sought, compensatory value	$ 5.0