Summary of Significant Accounting Policies - Environmental Recovery (Details) - Georgia Power [Member] - USD ($) $ in Millions	1 Months Ended
	Dec. 31, 2013	Dec. 31, 2016
Accounting Policies [Line Items]
Environmental Exit Costs, Assets Previously Disposed, Liability for Remediation		$ 17
Environmental Remediation Reserve [Member]
Accounting Policies [Line Items]
Costs Recovered Annually Under Rate Plan	$ 2
Other regulatory assets current [Member]
Accounting Policies [Line Items]
Environmental Regulatory Assets		2
Other regulatory assets deferred [Member]
Accounting Policies [Line Items]
Environmental Regulatory Assets		$ 33