Rate and Other Regulatory Matters (Narrative) (Detail) - USD ($) $ in Millions	1 Months Ended				9 Months Ended
	Sep. 30, 2023	Apr. 30, 2023	Mar. 31, 2023	Jan. 31, 2023	Sep. 30, 2023	Feb. 28, 2023
Rate And Other Regulatory Matters [Line Items]
South Carolina Commission Order for Increase/Decrease of Total Fuel Cost Component of Retail Electric Rates to produce a projected under-recovery						$ 176
Annual increase (decrease) in pension cost rider		$ 24
Estimated electric transmission cost			$ 55
Amount of increase in proposed base rate	$ 9		$ 19
Percentage of currently authorized ROE	9.49%		10.25%
Percentage of proposed ROE			10.38%
Regulatory asset recovery assessment end period					2047
Storm restoration recovery period					10 years
Reserve For Refunds To Electric Utility Customers [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers recovery period					11 years
Deferred Losses or Gains On Interest Rate Derivatives [Member]
Rate And Other Regulatory Matters [Line Items]
Changes in fair value and payments of interest rate derivatives not designed, amortized to interest, year					2065
Monetization Of Guaranty Settlement [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers recovery period					20 years
End period for recovery					2039
Income Taxes Refundable Through Future Rates [Member]
Rate And Other Regulatory Matters [Line Items]
Remaining lives of related property period					85 years
NND Project Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers recovery period					20 years
End period for recovery					2039
Deferred Employee Benefit Plan Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Regulatory asset recovery assessment end period					2044
Average service period expected to recover other deferred benefit costs					11 years
Other Unrecovered Plant [Member]
Rate And Other Regulatory Matters [Line Items]
Amortization of carrying value of coal-fired generating unit					2025
New expected amortization of carrying value of coal-fired generating unit					2033
Advanced Metering Infrastructure Project [Member]
Rate And Other Regulatory Matters [Line Items]
New expected amortization of carrying value of coal-fired generating unit					2028
Demand Side Management Programs [Member]
Rate And Other Regulatory Matters [Line Items]
Recovery period of regulatory asset	3 years				3 years
Asset Retirement Obligation Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Recovery period of regulatory asset	105 years				105 years
Environmental Remediation Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Recovery period of regulatory asset	29 years				29 years
Deferred Transmission Operating Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Recovery period of regulatory asset	42 years				42 years
Rider D S M [Member]
Rate And Other Regulatory Matters [Line Items]
South Carolina Commission Order, Annual DSM Program Rate Rider Recovery Amount				$ 46
South Carolina Commission [Member]
Rate And Other Regulatory Matters [Line Items]
South Carolina Commission Order for Increase/Decrease of Total Fuel Cost Component of Retail Electric Rates to produce a projected under-recovery		$ 121