Property, Plant And Equipment (Schedule Of Property, Plant And Equipment) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Subject to depletion	$ 5,635,307		$ 5,635,307		$ 5,687,557
Unevaluated costs	218,398		218,398		221,605
Accumulated depletion	(5,245,133)		(5,245,133)		(5,268,719)
Net oil and gas properties	608,572		608,572		640,443
Pipelines and processing facilities	332,710		332,710		347,093
General properties	71,049		71,049		72,125
Accumulated depreciation	(199,851)		(199,851)		(198,856)
Net other property and equipment	203,908		203,908		220,362
Property, plant and equipment, net of accumulated depletion and depreciation	812,480		812,480		860,805
Impairment of Oil and Gas Properties	135	0	135	0
Midstream [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net of accumulated depletion and depreciation	89,362		89,362		97,118
Impairment of Oil and Gas Properties	135		135
Property, Plant and Equipment, Other Types [Member] | Midstream [Member]
Property, Plant and Equipment [Line Items]
Impairment of Oil and Gas Properties			$ 100