Property And Equipment (Summary Of Oil And Gas Properties Not Subject To Amortization) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	$ 952,697	$ 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	6,160
Bakken [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	312
Southern Louisiana [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	914
Ohio [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	945,261
Other [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	$ 50