Utility Plant and Nonutility Property (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	6 Months Ended
	May 31, 2019	Sep. 30, 2019	Jun. 30, 2019
Utility Plant And Non Utility Property [Line Items]
Total consideration from sale of assets	$ 7
Contractual term of agreement to use brand			10 years
Summer
Utility Plant And Non Utility Property [Line Items]
Percentage of direct expenses			66.70%
Percentage of ownership interest	66.70%
NND Project | Summer
Utility Plant And Non Utility Property [Line Items]
Percentage of ownership interest	55.00%
Santee Cooper | NND Project | Summer
Utility Plant And Non Utility Property [Line Items]
Percentage of ownership interest	11.70%
Ownership interest purchased	$ 8
Warranty Service Contract Assets | Scenario Forecast
Utility Plant And Non Utility Property [Line Items]
Expected gain on sale of assets		$ 7
Expected gain on sale of assets, after tax		$ 5