Vogtle Units No. 3 and No. 4 Construction Project (Details) - Vogtle Units No. 3 & No. 4 $ in Thousands		3 Months Ended	12 Months Ended
	Apr. 15, 2020	Mar. 31, 2020 USD ($) unit	Dec. 31, 2008 unit MW
Public Utility Property Plant and Equipment
Ownership interest (as a percent)		30.00%
Total investment in additional Vogtle units		$ 5,200,000
Estimated project-level construction contingency		240,000
Allocated project level contingency		451,000
Allocated project level contingency from interest in project level budget		135,000
Incremental Allocation		144,000
Interest in project level budget, incremental allocation		43,000
Expected restructuring cost		$ 13,000
Subsequent Event
Public Utility Property Plant and Equipment
Workforce reduction, percent	20.00%
Ownership participation agreement
Public Utility Property Plant and Equipment
Number of additional nuclear units | unit		2
Ownership interest (as a percent)		30.00%
Project budget		$ 7,500,000
Project extension term		1 year
EPC Agreement | Westinghouse Electric Company LLC and Stone & Webster, Inc.
Public Utility Property Plant and Equipment
Number of nuclear units | unit			2
Generating capacity of each nuclear unit | MW			1,100
Services Agreement | Westinghouse Electric Company LLC and Stone & Webster, Inc.
Public Utility Property Plant and Equipment
Written notice period for termination of agreement		30 days
Global Amendments To Term Sheet
Public Utility Property Plant and Equipment
Percentage of costs disallowed for recovery		6.00%
Global Amendments To Term Sheet | Minimum
Public Utility Property Plant and Equipment
Construction contingency estimate		$ 800,000
Percentage of ownership approval to change primary construction contractor		90.00%