Segment Disclosures Reconciliation of Segment Assets to Consolidated (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Segment assets:
Total assets	$ 44,629	$ 46,040
Transmission And Gulf Of Mexico [Member]
Segment assets:
Total assets	18,656	18,796
Northeast G And P [Member]
Segment assets:
Total assets	14,702	15,399
West [Member]
Segment assets:
Total assets	10,619	11,265
Other [Member]
Segment assets:
Total assets	1,309	1,151
Intersegment Elimination [Member]
Segment assets:
Total assets	$ (657)	$ (571)