Revenue Recognition - Management Program (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2018
Vogtle Units No. 3 & No. 4
Operating revenues
Amounts billed under rate management program	$ 3,861	$ 3,857
Cumulative recovery of financing costs	115,497
Vogtle New Units
Operating revenues
Cumulative recovery of financing costs	360,272
Rate management program, additional collection period			5 years
Rate management program, billing period			5 years
Amounts billed under additional rate management program	$ 2,944	$ 40,044