Revenue Recognition - Management Program (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Vogtle Units No. 3 & No. 4
Operating revenues
Amounts billed under rate management program	$ 3,981	$ 5,563
Cumulative recovery of financing costs	85,241
Vogtle New Units
Operating revenues
Cumulative recovery of financing costs	116,975
Rate management program, additional collection period			5 years
Rate management program, billing period			5 years
Amounts billed under additional rate management program	$ 28,488	$ 11,690