Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Balance Sheet) (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
SCANA Energy Marketing, Inc. [Member]
Related Party Transaction [Line Items]
Payable to affiliates	$ 0	$ 14
DESS [Member]
Related Party Transaction [Line Items]
Payable to affiliates	47	38
Canadys Refined Coal [Member]
Related Party Transaction [Line Items]
Receivable from affiliates	13	7
Payable to affiliates	$ 13	$ 7

Amount of receivables due from an entity that is affiliated with the reporting entity by means of direct or indirect ownership, due within 1 year (or 1 business cycle).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6918054&loc=d3e56071-112765

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
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-Publisher FASB
-Name Accounting Standards Codification
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Name:	us-gaap_DueFromAffiliateCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant