Natural Gas And Oil Producing Activities (Schedule Of Proved Developed And Undeveloped Oil And Gas Reserve Quantities) (Details) ft³ in Billions	12 Months Ended
Dec. 31, 2015 MBbls ft³	Dec. 31, 2014 MBbls ft³	Dec. 31, 2013 MBbls ft³	Dec. 31, 2012 MBbls ft³
Reserve Quantities [Line Items]
Revisions of previous estimates \| ft³	(4,083)	543
Extensions, discoveries and other additions \| ft³	592	1,693	3,285
Production \| ft³		(768)	(657)	(565)
Natural Gas [Member]
Reserve Quantities [Line Items]
Proved reserves, beginning of year \| ft³	9,809	6,974	4,017
Revisions of previous estimates \| ft³	(3,458)	542	325
Extensions, discoveries and other additions \| ft³	546	1,692	3,284
Production \| ft³	(899)	(766)	(656)
Acquisition of reserves in place \| ft³	97	1,367	4
Disposition of reserves in place \| ft³	(178)
Proved reserves, end of year \| ft³	5,917	9,809	6,974	4,017
Proved Developed Reserves [Abstract]
Beginning of year \| ft³	5,675	4,237	3,196
End of year \| ft³	5,474	5,675	4,237	3,196
Proved Undeveloped Reserves [Abstract]
Beginning of year \| ft³	4,134	2,737	821
End of year \| ft³	443	4,134	2,737	821
Oil [Member]
Reserve Quantities [Line Items]
Proved reserves, beginning of year	37,615	373	244
Revisions of previous estimates	(28,394)	(14)	38
Extensions, discoveries and other additions	1,367	250	229
Production	(2,265)	(235)	(138)
Acquisition of reserves in place	525	37,246
Disposition of reserves in place	(95)	(5)
Proved reserves, end of year	8,753	37,615	373	244
Proved Developed Reserves [Abstract]
Beginning of year	7,445	372	243
End of year	8,753	7,445	372	243
Proved Undeveloped Reserves [Abstract]
Beginning of year	30,170	1	1
End of year		30,170	1	1
NGL [Member]
Reserve Quantities [Line Items]
Proved reserves, beginning of year	118,699
Revisions of previous estimates	(75,664)	66	50
Extensions, discoveries and other additions	6,274	48
Production	(10,702)	(231)	(50)
Acquisition of reserves in place	2,340	118,816
Disposition of reserves in place
Proved reserves, end of year	40,947	118,699
Proved Developed Reserves [Abstract]
Beginning of year	38,632
End of year	40,947	38,632
Proved Undeveloped Reserves [Abstract]
Beginning of year	80,067
End of year		80,067

Proved Developed Reserves [Abstract]

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Proved Undeveloped Reserves [Abstract]

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Additions to proved reserves that result from (1) extension of the proved acreage of previously discovered (old) reservoirs through additional drilling in periods after discovery and (2) discovery of new fields with proved reserves or of new reservoirs of proved reserves in old fields.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 5
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=51678428&loc=d3e61831-109447

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The net quantity of proved reserves as of the balance sheet date. Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
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-URI http://asc.fasb.org/extlink&oid=51678428&loc=d3e61831-109447

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Production of proved reserves.

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Purchase of minerals in place.

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Revisions represent changes in previous estimates of proved reserves, either upward or downward, resulting from new information (except for an increase in proved acreage) normally obtained from development drilling and production history or resulting from change in economic factors.

+ References

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Sales of minerals in place.

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Net quantities of an enterprise's interests in proved developed reserves of either crude oil (including condensate and natural gas liquids), natural gas, synthetic oil and gas, or other nonrenewable natural resource that is intended to be upgraded into synthetic oil and gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned are included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities does not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities is defined as "barrels" for oil and synthetic oil reserves or "cubic feet" or "cubic meters" for natural gas and synthetic gas reserves.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Net quantities of an enterprise's interests in proved undeveloped reserves of either crude oil (including condensate and natural gas liquids), natural gas, synthetic oil and gas, or other renewable natural resource that is intended to be upgraded into synthetic oil and gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned are included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities does not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities is defined as "barrels" for oil and synthetic oil reserves or "cubic feet" or "cubic meters" for natural gas and synthetic gas reserves.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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