Summary of Significant Accounting Policies - Schedule of Concentration of Revenue (Details) - Southern Power - Sales Revenue, Goods, Net - Customer Concentration Risk	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Georgia Power
Concentration Risk [Line Items]
Percentage of total revenues for top three customers	9.80%	11.30%	16.50%
Duke Energy Corporation
Concentration Risk [Line Items]
Percentage of total revenues for top three customers	6.80%	6.70%	7.80%
Southern California Edison
Concentration Risk [Line Items]
Percentage of total revenues for top three customers	6.20%
Morgan Stanley Capital Group
Concentration Risk [Line Items]
Percentage of total revenues for top three customers		4.50%
San Diego Gas & Electric Company
Concentration Risk [Line Items]
Percentage of total revenues for top three customers			5.70%