DERIVATIVE FINANCIAL INSTRUMENTS Fair Value on Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 4.0	$ 59.0
Derivative Liability, Fair Value, Gross Liability	25.0	38.0
Interest Rate Contract
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0.0	54.0
Derivative Liability, Fair Value, Gross Liability	23.0	32.0
Commodity Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	2.0	1.0
Derivative Liability, Fair Value, Gross Liability	0.0	3.0
Other Energy Management Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	2.0	4.0
Derivative Liability, Fair Value, Gross Liability	2.0	3.0
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1.0	0.0
Derivative Liability, Fair Value, Gross Liability	20.0	30.0
Designated as Hedging Instrument [Member] \| Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount	106.8	111.2
Designated as Hedging Instrument [Member] \| Interest Rate Contract \| Derivative Financial Instruments, Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	3.0	3.0
Designated as Hedging Instrument [Member] \| Interest Rate Contract \| Other Deferred Credits and Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	17.0	24.0
Designated as Hedging Instrument [Member] \| Commodity Contract [Member] \| Prepayments [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1.0	0.0
Derivative Liability, Fair Value, Gross Liability	0.0	2.0
Designated as Hedging Instrument [Member] \| Commodity Contract [Member] \| Other Current Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		0.0
Derivative Liability, Fair Value, Gross Liability		1.0
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	3.0	59.0
Derivative Liability, Fair Value, Gross Liability	5.0	8.0
Not Designated as Hedging Instrument [Member] \| Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount	35.0	735.0
Not Designated as Hedging Instrument [Member] \| Interest Rate Contract \| Derivative Financial Instruments, Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability		1.0
Not Designated as Hedging Instrument [Member] \| Interest Rate Contract \| Derivative Financial Instruments, Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		54.0
Not Designated as Hedging Instrument [Member] \| Interest Rate Contract \| Other Deferred Credits and Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	3.0	4.0
Not Designated as Hedging Instrument [Member] \| Commodity Contract [Member] \| Prepayments [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1.0
Not Designated as Hedging Instrument [Member] \| Commodity Contract [Member] \| Other Current Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		1.0
Not Designated as Hedging Instrument [Member] \| Other Energy Management Contract [Member] \| Derivative Financial Instruments, Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	1.0	2.0
Not Designated as Hedging Instrument [Member] \| Other Energy Management Contract [Member] \| Other Deferred Debits and Other Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1.0	1.0
Not Designated as Hedging Instrument [Member] \| Other Energy Management Contract [Member] \| Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	1.0
Not Designated as Hedging Instrument [Member] \| Other Energy Management Contract [Member] \| Prepayments [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		0.0
Derivative Liability, Fair Value, Gross Liability		1.0
Not Designated as Hedging Instrument [Member] \| Other Energy Management Contract [Member] \| Other Current Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1.0	3.0
Derivative Liability, Fair Value, Gross Liability		0.0
SCEG \| Interest Rate Contract
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0.0	54.0
Derivative Liability, Fair Value, Gross Liability	10.0	15.0
SCEG \| Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	7.0	10.0
SCEG \| Designated as Hedging Instrument [Member] \| Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount	36.4	36.4
SCEG \| Designated as Hedging Instrument [Member] \| Interest Rate Contract \| Derivative Financial Instruments, Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	1.0	1.0
SCEG \| Designated as Hedging Instrument [Member] \| Interest Rate Contract \| Other Deferred Credits and Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	6.0	9.0
SCEG \| Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0.0	54.0
Derivative Liability, Fair Value, Gross Liability	3.0	5.0
SCEG \| Not Designated as Hedging Instrument [Member] \| Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount	35.0	735.0
SCEG \| Not Designated as Hedging Instrument [Member] \| Interest Rate Contract \| Derivative Financial Instruments, Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability		1.0
SCEG \| Not Designated as Hedging Instrument [Member] \| Interest Rate Contract \| Derivative Financial Instruments, Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		54.0
SCEG \| Not Designated as Hedging Instrument [Member] \| Interest Rate Contract \| Other Deferred Credits and Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ 3.0	$ 4.0

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (a),(c)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226000-175313

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=82924980&loc=SL51823488-111719

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959

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-Name Accounting Standards Codification
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