Acquisitions and Dispositions (Expected Sale of Interest in Cove Point) (Narrative) (Detail) - Cove Point - Subsequent Event $ in Billions	1 Months Ended
Oct. 31, 2019 USD ($)
Business Acquisition And Dispositions [Line Items]
Ownership interest percentage of limited partner interests	25.00%
Cash consideration from sale of noncontrolling interest	$ 2.1

Percentage investment held by members or limited partners of limited liability company (LLC) or limited partnership (LP).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

Name:	us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration