Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Balance Sheet) (Detail) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Derivative assets with affiliates	$ 45	$ 28
Solar Affiliates [Member]
Related Party Transaction [Line Items]
Payable to affiliates	1	1
Nuclear Affiliates [Member]
Related Party Transaction [Line Items]
Receivable from affiliates	1	1
D E S And D E S S
Related Party Transaction [Line Items]
Payable to affiliates	24	30
Public Service Company Of North Carolina Incorporated
Related Party Transaction [Line Items]
Receivable from affiliates	5	60
Dominion Energy
Related Party Transaction [Line Items]
Payable to affiliates	$ 2	$ 1

Amount of payable due to an entity that is affiliated with the reporting entity by means of direct or indirect ownership. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(1))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(a)(5))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04(12)(b)(3))
-URI http://asc.fasb.org/extlink&oid=120401414&loc=d3e603758-122996

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant