Leases (Lease Assets and Liabilities Recorded in Consolidated Balance Sheets) (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Lessee Lease Disclosure [Line Items]
Finance lease assets, accumulated amortization	$ 114	$ 81
Virginia Electric and Power Company
Lessee Lease Disclosure [Line Items]
Finance lease assets, accumulated amortization	$ 33	$ 18

Amount of accumulated amortization of right-of-use asset from finance lease.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=128292326&loc=SL77918686-209980

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 4
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=123391704&loc=SL77918638-209977

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