Segment Disclosures Reconciliation of Segment Assets to Consolidated (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Segment assets:
Total assets	$ 45,970	$ 45,302
Northeast G And P [Member]
Segment assets:
Total assets	15,301	14,526
Atlantic Gulf [Member]
Segment assets:
Total assets	16,441	16,346
West [Member]
Segment assets:
Total assets	13,834	13,948
Other [Member]
Segment assets:
Total assets	782	849
Intersegment Elimination [Member]
Segment assets:
Total assets	$ (388)	$ (367)