Revenue Recognition - Management Program (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2018
Vogtle Units No. 3 & No. 4
Operating revenues
Amounts billed under rate management program	$ 7,729	$ 7,893
Cumulative recovery of financing costs	103,672
Vogtle New Units
Operating revenues
Cumulative recovery of financing costs	294,127
Rate management program, additional collection period			5 years
Rate management program, billing period			5 years
Amounts billed under additional rate management program	$ 80,087	$ 60,939