Vogtle Units No. 3 and No. 4 Construction Project - Project Budget and Actual Costs (Details) - Vogtle Units No. 3 & No. 4 - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2021
Project Budget
Project-Level Contingency	$ 78.0	$ 32.0	$ 112.5
Remaining Project Budget
Proceeds from guarantee agreement				$ 1,100.0
Jointly Owned Nuclear Power Plant
Project Budget
Construction Costs				6,013.0
Financing Costs				1,735.0
Total Costs				7,748.0
Project-Level Contingency				78.0
Oglethorpe-Level Contingency				424.0
Total Contingency				502.0
Total Contingency				8,250.0
Actual Costs
Construction Costs				5,145.0
Financing Costs				1,385.0
Total Costs				6,530.0
Project-Level Contingency				0.0
Oglethorpe-Level Contingency				0.0
Total Contingency				0.0
Totals				6,530.0
Remaining Project Budget
Construction Costs				868.0
Financing Costs				350.0
Total Costs				1,218.0
Project-Level Contingency				78.0
Oglethorpe-Level Contingency				424.0
Total Contingency				502.0
Totals				$ 1,720.0