Regulatory Matters - GPC Nuclear Construction Cost and Schedule (Details) - GEORGIA POWER CO - Plant Vogtle Units 3 And 4 - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2021	Jun. 30, 2020
Loss Contingencies [Line Items]
Base project capital cost forecast	$ 8,619
Construction contingency estimate	136
Total project capital cost forecast	8,755
Net investment as of March 31, 2021	(7,560)
Remaining estimate to complete	1,195
Expected capitalized costs	250
Capitalized interest accrued	118
Twenty Third Vogtle Construction Monitoring Report
Loss Contingencies [Line Items]
Guarantor obligations	1,700	$ 1,700
Customer refund	$ 188	$ 188