Property And Equipment, Net (Schedule Of Property And Equipment) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Abstract]
Proved oil and gas properties	$ 1,905,658	$ 1,713,827
Accumulated depreciation, depletion and amortization	(606,320)	(561,279)
Proved oil and gas properties, net	1,299,338	1,152,548
Unproved properties, not being amortized
Unevaluated leasehold costs	281,197	238,833
Exploratory wells in progress	33,415	43,803
Capitalized interest	43,660	41,052
Total unproved properties, not being amortized	358,272	323,688
Other property and equipment	20,098	17,079
Accumulated depreciation	(5,983)	(5,641)
Other property and equipment, net	14,115	11,438
TOTAL PROPERTY AND EQUIPMENT, NET	$ 1,671,725	$ 1,487,674