RATE AND OTHER REGULATORY MATTERS (Details) $ in Millions	3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2016 USD ($) MW	Sep. 30, 2015 USD ($)	Jun. 30, 2016 USD ($)	Sep. 30, 2016 USD ($) MW	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2013
Rate Matters [Line Items]
Reclassifications, Cash Flow Statement, Regulatory Assets, Use Of Cash				$ 66.0
Carrying cost recovery				(12.0)	$ (9.0)
Regulatory Assets, Noncurrent	$ 2,202.0			$ 2,202.0		$ 1,937.0
MPG environmental remediation				18
SCEG
Rate Matters [Line Items]
Public Utilities changes in Retail Natural Gas Rates Approved under RSA				$ 4.1
Public Utilities, Percent Increase (Decrease) in Retail Natural Gas Rates				1.20%
Public Utilities, Rate Calculation Basis				12-month rolling average
Reclassifications, Cash Flow Statement, Regulatory Assets, Use Of Cash				$ 66.0
Capacity of renewable energy facilities by 2020 | MW	80			80
SCPSC Order Reduction Of Total Fuel Cost Component Of Retail Electric Rates To Reflect Lower Projected Fuel Costs And Eliminate Over-Collection Balances			$ 61.0
SCPSC Order, Recovery Of Projected DER Program Costs			6.9
Carrying costs on deferred income tax assets	$ 3.5	$ 2.4		$ 10.0	6.5
Carrying cost recovery				(12.0)	$ (9.0)
Regulatory Assets, Noncurrent	2,114.0			$ 2,114.0		$ 1,857.0
Demand side management recovery period				5
SCPSC Order, Annual DSM Program Rate Rider Recovery Amount			37.6
Increased Project Costs Above SCPSC Sept 2015 Order			852.0
Increased Project Costs Re Fixed Price Option			505.0
Revised Requested Project Costs above SCPSC Sept 2015 Order				$ 846.0
Estimated Gross Const Cost With Fixed Price Option			$ 7,700.0
Public Utilties increase (decrease) in retail electric rates				$ 64.4
Public Utilities Percentage Change in Retail Electric Rates Approved under BLRA				2.70%
Public Utilities, Authorized Allowable Return on Common Equity, Percentage				10.50%		0.00%
PSNC Energy
Rate Matters [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount				$ 19.1
Public Utilities, Approved Rate Increase (Decrease), Percentage				4.39%
Public Utilities, Authorized Allowable Return on Common Equity, Percentage				9.70%
Deferred Income Tax Charges [Member]
Rate Matters [Line Items]
Regulatory Assets, Noncurrent	301.0			$ 301.0		$ 298.0
Regulatory Noncurrent Asset Amortization Period				85 years
Deferred Income Tax Charges [Member] | SCEG
Rate Matters [Line Items]
Regulatory Assets, Noncurrent	294.0			$ 294.0		291.0
Asset Retirement Obligation Costs [Member]
Rate Matters [Line Items]
Regulatory Assets, Noncurrent	402.0			$ 402.0		405.0
Regulatory Noncurrent Asset Amortization Period				110 years
Asset Retirement Obligation Costs [Member] | SCEG
Rate Matters [Line Items]
Regulatory Assets, Noncurrent	380.0			$ 380.0		384.0
Environmental Restoration Costs [Member]
Rate Matters [Line Items]
Regulatory Assets, Noncurrent	33.0			33.0		42.0
Environmental Restoration Costs [Member] | SCEG
Rate Matters [Line Items]
Regulatory Assets, Noncurrent	26.0			26.0		35.0
Pension costs, electric [Member] | SCEG
Rate Matters [Line Items]
Regulatory Noncurrent Asset Amortization Period							30 years
Defined Benefit Plan, Deferred Debit Attributable to Share of Regulatory Authority	63.0			63.0
Pension costs, gas [Member] | SCEG
Rate Matters [Line Items]
Regulatory Noncurrent Asset Amortization Period							14 years
Defined Benefit Plan, Deferred Debit Attributable to Share of Regulatory Authority	14.0			14.0
Pension Costs [Member]
Rate Matters [Line Items]
Regulatory Assets, Noncurrent	311.0			311.0		325.0
Pension Costs [Member] | SCEG
Rate Matters [Line Items]
Regulatory Assets, Noncurrent	282.0			$ 282.0		295.0
Regulatory Noncurrent Asset Amortization Period				12 years
Other Regulatory Assets [Member]
Rate Matters [Line Items]
Regulatory Assets, Noncurrent	173.0			$ 173.0		144.0
Regulatory Noncurrent Asset Amortization Period				30 years
Other Regulatory Assets [Member] | SCEG
Rate Matters [Line Items]
Regulatory Assets, Noncurrent	$ 150.0			$ 150.0		$ 129.0