Commitments And Contingencies (Narrative) (Details)	9 Months Ended
	Sep. 30, 2017 USD ($) plaintiff item
Commitments And Contingencies [Line Items]
Obligation under transportation agreements	$ 8,858,000,000
Guarantee obligations relative to the firms transportation agreements and gathering project and services	832,000,000
Indemnification liability	$ 0
Arkansas Royalty Litigation [Member] | Arkansas State Court [Member]
Commitments And Contingencies [Line Items]
Number of actions | item	2
Number of cases | item	3
Number of plaintiffs | plaintiff	248
Number of cases removed to federal court | item	2
Pending Regulatory Approval and/or Construction [Member]
Commitments And Contingencies [Line Items]
Obligation under transportation agreements	$ 3,722,000,000