Segment Disclosures Reconciliation of Segment Assets to Consolidated (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Segment assets:
Total assets	$ 46,281	$ 45,302
Northeast G And P [Member]
Segment assets:
Total assets	15,445	14,526
Atlantic Gulf [Member]
Segment assets:
Total assets	16,888	16,346
West [Member]
Segment assets:
Total assets	13,550	13,948
Other [Member]
Segment assets:
Total assets	928	849
Intersegment Elimination [Member]
Segment assets:
Total assets	$ (530)	$ (367)