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Property And Equipment (Summary Of Oil And Gas Properties Not Subject To Amortization) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	$ 869,879	$ 626,300	$ 626,295
Colorado [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	6,088
Bakken [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	301
Southern Louisiana [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	789
Ohio [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	862,655
Other [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	$ 46