Property And Equipment (Schedule Of Property And Equipment) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Oil and Gas Property, Full Cost Method, Net [Abstract]
Oil and gas properties under the full cost method	$ 1,416,997	$ 1,265,234
Computers, furniture and fixtures	8,733	8,863
Total property and equipment	1,425,730	1,274,097
Accumulated depreciation, depletion and amortization	(346,824)	(270,656)
Net property and equipment	1,078,906	1,003,441
Subject To Amortization [Member]
Oil and Gas Property, Full Cost Method, Net [Abstract]
Oil and gas properties under the full cost method	1,028,380	915,801
Not Subject To Amortization [Member] | Incurred in 2013
Oil and Gas Property, Full Cost Method, Net [Abstract]
Oil and gas properties under the full cost method	68,193
Not Subject To Amortization [Member] | Incurred in 2012
Oil and Gas Property, Full Cost Method, Net [Abstract]
Oil and gas properties under the full cost method	142,218	141,837
Not Subject To Amortization [Member] | Incurred in 2011
Oil and Gas Property, Full Cost Method, Net [Abstract]
Oil and gas properties under the full cost method	99,183	107,510
Not Subject To Amortization [Member] | Incurred prior to 2011
Oil and Gas Property, Full Cost Method, Net [Abstract]
Oil and gas properties under the full cost method	$ 79,023	$ 100,086