Revenue Recognition - Management Program (Details) - USD ($)	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2018
Vogtle Units No. 3 & No. 4
Operating revenues
Amounts billed under rate management program	$ 7,893,000	$ 8,966,000
Cumulative recovery of financing costs	89,152,000
Vogtle New Units
Operating revenues
Cumulative recovery of financing costs	149,426,000
Rate management program, additional collection period			5 years
Rate management program, billing period			5 years
Amounts billed under additional rate management program	$ 60,939,000	$ 23,380,000