Revenue Recognition - Management Program (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Vogtle Units No. 3 & No. 4
Operating revenues
Amounts billed under rate management program	$ 5,563,000	$ 12,229,000
Cumulative recovery of financing costs	71,879,000
Vogtle New Units
Operating revenues
Amounts billed under additional rate management program	$ 11,690,000	$ 15,435,000