Acquisitions and Dispositions (Sale of Interest in Cove Point) (Narrative) (Detail) - USD ($) $ in Billions	1 Months Ended
	Dec. 31, 2019	Oct. 31, 2019	Dec. 31, 2018
Business Acquisition And Dispositions [Line Items]
Cash consideration from sale of noncontrolling interest	$ 2.1
Cove Point [Member]
Business Acquisition And Dispositions [Line Items]
Ownership interest percentage of limited partner interests		25.00%	25.00%
Cash consideration from sale of noncontrolling interest		$ 2.1