Natural Gas And Oil Producing Activities (Unaudited) (Schedule Of Proved Developed And Undeveloped Oil And Gas Reserve Quantities) (Details)	12 Months Ended
Dec. 31, 2014 ft3	Dec. 31, 2013 ft3	Dec. 31, 2012 ft3	Dec. 31, 2011 ft3
Reserve Quantities [Line Items]
Revisions of previous estimates		326,000,000,000
Extensions, discoveries and other additions	1,693,000,000,000	3,285,000,000,000	920,000,000,000
Production	768,000,000,000	657,000,000,000	565,000,000,000	500,000,000,000
Natural Gas [Member]
Reserve Quantities [Line Items]
Proved reserves, beginning of year	6,974,000,000,000	4,017,000,000,000	5,887,000,000,000
Revisions of previous estimates	542,000,000,000	325,000,000,000	(2,088,000,000,000)
Extensions, discoveries and other additions	1,691,000,000,000	3,283,000,000,000	918,000,000,000
Production	(765,000,000,000)	(655,000,000,000)	(564,000,000,000)
Acquisition of reserves in place	1,367,000,000,000	4,000,000,000
Disposition of reserves in place			(136,000,000,000)
Proved reserves, end of year	9,809,000,000,000	6,974,000,000,000	4,017,000,000,000
Proved Developed Reserves [Abstract]
Beginning of year	4,237,000,000,000	3,196,000,000,000	3,254,000,000,000
End of year	5,675,000,000,000	4,237,000,000,000	3,196,000,000,000
Proved Undeveloped Reserves [Abstract]
Beginning of year	2,737,000,000,000	821,000,000,000	2,633,000,000,000
End of year	4,134,000,000,000	2,737,000,000,000	821,000,000,000
Oil [Member]
Reserve Quantities [Line Items]
Proved reserves, beginning of year	373	244	996
Revisions of previous estimates	(14)	38	(44)
Extensions, discoveries and other additions	250	229	154
Production	(235)	(138)	(83)
Acquisition of reserves in place	37,246
Disposition of reserves in place	(5)		(779)
Proved reserves, end of year	37,615	373	244
Proved Developed Reserves [Abstract]
Beginning of year	372	243	983
End of year	7,445	372	243
Proved Undeveloped Reserves [Abstract]
Beginning of year	1	1	13
End of year	30,170	1	1
NGL [Member]
Reserve Quantities [Line Items]
Proved reserves, beginning of year
Revisions of previous estimates	66	50
Extensions, discoveries and other additions	48
Production	(231)	(50)
Acquisition of reserves in place	118,816
Disposition of reserves in place
Proved reserves, end of year	118,699
Proved Developed Reserves [Abstract]
Beginning of year
End of year	38,632
Proved Undeveloped Reserves [Abstract]
Beginning of year
End of year	80,067

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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.

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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.

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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.

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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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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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