Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary Of Significant Accounting Policies [Line Items]
Derivative collateral held		$ 0
Cash collateral posted		0
ASC 606 Revenue from Contracts with Customers [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated impact on upstream revenues and production expense		250,000,000	$ 250,000,000
ASC 606 Revenue from Contracts with Customers [Member] | Forecasted [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated impact on upstream revenues and production expense	$ 250,000,000
ASU 2017-07, Compensation – Retirement Benefits [Member]
Summary Of Significant Accounting Policies [Line Items]
Reclassification of non-service cost components of net periodic benefit costs		$ 7,000,000	$ 14,000,000	$ 16,000,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Other property and equipment, useful life		3 years
Finite lived intangible asset useful life		10 years
Minimum [Member] | General Partner And EnLink [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated net decrease in marketing and midstream revenues		6.00%
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Other property and equipment, useful life		60 years
Finite lived intangible asset useful life		20 years
Maximum [Member] | General Partner And EnLink [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated net decrease in marketing and midstream revenues		10.00%
Major Customer Accounting For More Than 10 Percent Of Operating Revenues [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage		0.00%	0.00%	0.00%