Segment Disclosures Reconciliation of Segment Assets to Consolidated (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Segment assets:
Total assets	$ 44,320	$ 46,040
Transmission And Gulf Of Mexico [Member]
Segment assets:
Total assets	19,246	18,796
Northeast G And P [Member]
Segment assets:
Total assets	14,526	15,399
West [Member]
Segment assets:
Total assets	10,745	11,265
Other [Member]
Segment assets:
Total assets	756	1,151
Intersegment Elimination [Member]
Segment assets:
Total assets	$ (953)	$ (571)