SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) shares in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) MW shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares
Significant Accounting Policies
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 30,000,000	$ 35,000,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents			$ 115,000,000
Utilities Operating Expense, Maintenance and Operations, Affiliate			18,400,000
Cost, Maintenance			16,300,000	$ 26,100,000
Public Utilities Percentage Change in Retail Electric Rates Approved under BLRA				18.00%
Reclassification Operations and Maintenance Expense				$ (9,000,000)	$ (14,000,000)
Long-term Debt, Current Maturities			59,000,000	727,000,000
Short-term borrowings			173,000,000	350,000,000
Regulated Operating Revenue, Gas			934,000,000	874,000,000	788,000,000
Decommissioning Liability, Noncurrent			625,800,000
Payments to Acquire Investments to be Held in Decommissioning Trust Fund			3,200,000
Unbilled Receivables, Current			217,500,000	220,900,000
Goodwill			210,000,000	210,000,000
Accumulated Amortization and Write-down, Goodwill			230,000,000
Nuclear refueling outage cost			28,600,000	23,200,000
Property, Plant and Equipment, Net			267,000,000	270,000,000
Reclassification Total Operating Expense				(9,000,000)	(14,000,000)
Reclassification Operating Income				9,000,000	14,000,000
Reclassification Other Income(Expense)				$ (9,000,000)	(14,000,000)
Change in Retail Electric Rates Approved Under BLRA			$ 2,768,000,000		$ 64,400,000
Public Utilities, Approved Return on Equity, Percentage		10.00%			10.50%
Reclassification from AOCI, Current Period, before Tax, Attributable to Parent	8,000,000
Asset Management and Supply Service Agreements
Public Utilities, Allowance for Funds Used During Construction, Rate			0.00%	0.00%	0.00%
Earnings Per Share
Weighted Average Shares Outstanding - Basic | shares			143	143	143
SCE&G
Significant Accounting Policies
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	15,000,000	$ 20,000,000
Utilities Operating Expense, Maintenance and Operations, Affiliate			$ 182,000,000	$ 180,000,000	$ 199,000,000
Reclassification Operations and Maintenance Expense				(7,000,000)	(12,000,000)
Long-term Debt, Current Maturities			14,000,000	723,000,000
Short-term borrowings			73,000,000	252,000,000
Regulated Operating Revenue, Gas			434,000,000	405,000,000	366,000,000
Environmental Remediation Costs Recognized in Regulatory Assets			23,300,000
Unbilled Receivables, Current			129,300,000	140,300,000
Property, Plant and Equipment, Net			$ 72,000,000	71,000,000
Reclassification Total Operating Expense				(7,000,000)	(12,000,000)
Reclassification Operating Income				7,000,000	12,000,000
Reclassification Other Income(Expense)				$ (7,000,000)	$ (12,000,000)
Reclassification from AOCI, Current Period, before Tax, Attributable to Parent	$ 1,000,000
Asset Management and Supply Service Agreements
Public Utilities, Allowance for Funds Used During Construction, Rate			0.00%	0.00%	0.00%
Genco [Member]
Significant Accounting Policies
Power Generation Capacity Megawatts | MW			605
Property, Plant and Equipment, Net			$ 500,000,000
PSNC Energy
Significant Accounting Policies
Natural gas inventory, carrying amount			$ 13,900,000	$ 11,500,000
PercentOfStorageFeesCreditedToRatePayers			75.00%
PSNC Energy
Significant Accounting Policies
Percentage of natural gas inventory held by counterparties under asset management and supply service agreements (as a percent)			46.00%	39.00%
Summer Station Unit 2 and Unit 3 [Domain]
Significant Accounting Policies
Jointly Owned Utility Plant, Proportionate Ownership Share			55.00%
SCE&G
Significant Accounting Policies
Amount accrued annually for nuclear fuel outages			$ 17,200,000
Electric Generation Equipment [Member]
Significant Accounting Policies
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			2.61%
Electric Generation Equipment [Member] | SCE&G
Significant Accounting Policies
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			2.61%
Gas Transmission Equipment [Member]
Significant Accounting Policies
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			2.47%
Gas Transmission Equipment [Member] | SCE&G
Significant Accounting Policies
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			2.74%
Gas Distribution Equipment [Member]
Significant Accounting Policies
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			2.48%
Gas Distribution Equipment [Member] | SCE&G
Significant Accounting Policies
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			2.41%
Natural Gas, Storage [Member]
Significant Accounting Policies
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			2.48%
Natural Gas, Storage [Member] | SCE&G
Significant Accounting Policies
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			2.71%
Other Energy Equipment [Member]
Significant Accounting Policies
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			5.64%
Other Energy Equipment [Member] | SCE&G
Significant Accounting Policies
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			3.18%