Property And Equipment (Summary Of Oil And Gas Properties Not Subject To Amortization) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 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	$ 872,113	$ 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	6,153
Bakken [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	307
Southern Louisiana [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	893
Ohio [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	864,710
Other [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Capitalized costs of oil and natural gas properties excluded from amortization	$ 50