Supplemental Natural Gas And Oil Information (Estimated Net Quantities Of Proved Natural Gas And Oil Reserves) (Details)	12 Months Ended
	Dec. 31, 2011 cubicFeet		Dec. 31, 2010 cubicFeet		Dec. 31, 2009 cubicFeet
Proved undeveloped reserves reclassified to non-proved category			208
Alabama and Michigan [Member]
Extensions, discoveries and other additions			51
High Mount Drilling [Member]
Extensions, discoveries and other additions			42
HighMount [Member]
Extensions, discoveries and other additions			238
Proved undeveloped reserves reclassified to non-proved category	152		346
Natural Gas (Bcf) [Member]
Proved developed and undeveloped reserves, net, beginning balance	945		1,521		1,694
Extensions, discoveries and other additions	26		251	[1]	39
Revisions of previous estimates	(107)	[2]	(407)	[3]	(141)	[4]
Production	(45)		(57)		(77)
Sales of reserves in place			(363)		(1)
Purchases of reserves in place					7
Proved developed and undeveloped reserves, net, ending balance	819		945		1,521
Proved developed reserves volume	623		741		1,231
NGLs and Oil (thousands of barrels) [Member]
Proved developed and undeveloped reserves, net, beginning balance	59,195		73,838		84,827
Extensions, discoveries and other additions	3,556		13,370	[1]	2,278
Revisions of previous estimates	(7,540)	[2]	(24,518)	[3]	(6,669)	[4]
Production	(2,976)		(3,263)		(3,679)
Sales of reserves in place	(11)		(232)		(2,919)
Purchases of reserves in place	167
Proved developed and undeveloped reserves, net, ending balance	52,391		59,195		73,838
Proved developed reserves volume	37,951		45,804		58,227
Natural Gas Equivalents (Bcfe) [Member]
Proved developed and undeveloped reserves, net, beginning balance	1,300		1,964		2,203
Extensions, discoveries and other additions	48		331	[1]	53
Revisions of previous estimates	(152)	[2]	(554)	[3]	(181)	[4]
Production	(63)		(77)		(99)
Sales of reserves in place			(364)		(19)
Purchases of reserves in place	1				7
Proved developed and undeveloped reserves, net, ending balance	1,134		1,300		1,964
Proved developed reserves volume	851		1,016		1,580

[1] HighMount added 238 Bcfe of proved undeveloped reserves from non-proved categories in 2010. These additions pertain to locations HighMount expects to drill during the next five years. Additionally, HighMount added 42 Bcfe primarily through drilling and the remaining 51 Bcfe in additions were associated with the Alabama and Michigan properties prior to sale.

[2] During 2011, HighMount reduced its proved developed and proved undeveloped reserves by 152 Bcfe as a result of recent higher decline rates of producing wells and economic factors such as lower gas prices and higher operating expenses.

[3] During 2010, HighMount reclassified 208 Bcfe of proved undeveloped reserves to a non-proved category due to certain wells reaching their five year maturity as a result of reduced drilling activity in 2009 and 2010. Additionally, HighMount reduced its proved developed and proved undeveloped reserves by 346 Bcfe as a result of higher production declines on its producing wells than previously anticipated.

[4] The 2009 revision is primarily attributable to lower 2009 average prices as compared to December 31, 2008. The lower 2009 average prices caused the reclassification of some proven undeveloped reserves.