Property And Equipment, Net (Schedule Of Property And Equipment) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Proved properties	$ 4,817,044	$ 4,687,416
Accumulated depreciation, depletion and amortization and impairments	(3,445,709)	(3,392,749)
Proved properties, net	1,371,335	1,294,667
Unproved properties, not being amortized
Unevaluated leasehold and seismic costs	221,039	211,067
Exploratory wells in progress	0	0
Capitalized interest	32,231	29,894
Total unproved properties, not being amortized	253,270	240,961
Other property and equipment	23,240	23,127
Accumulated depreciation	(13,641)	(12,995)
Other property and equipment, net	9,599	10,132
Total property and equipment, net	$ 1,634,204	$ 1,545,760