Acquisitions and Dispositions - Schedule of Construction Projects (Details) - SOUTHERN POWER CO - MW	1 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2021	Mar. 31, 2022	Sep. 30, 2021	Dec. 31, 2020
Garland Solar Storage
Business Acquisition [Line Items]
Nameplate capacity placed in service (in MWs)	45				45
Garland Solar Storage | Scenario, Forecast
Business Acquisition [Line Items]
Nameplate capacity placed in service (in MWs)		43
Garland Solar Storage | Scenario, Forecast | Subsequent Event
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW)		88	88
PPA Contract Period			20 years
Tranquillity Solar Storage | Scenario, Forecast | Subsequent Event
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW)				72
PPA Contract Period				20 years
Glass Sands | Scenario, Forecast | Subsequent Event
Business Acquisition [Line Items]
Approximate Nameplate Capacity (MW)		118	118
PPA Contract Period		12 years
Glass Sands | Glass Sands
Business Acquisition [Line Items]
Ownership percentage by parent						100.00%