Property And Equipment (Details Textuals) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Property and Equipment (Textuals) [Abstract]
Description of Current Status of Project	Our 2012 property acquisition costs were primarily related to the fair value allocated to our Hartzog Draw and Thompson fields. Our 2010 property acquisition costs were primarily related to the fair value allocated to CO2 tertiary potential at our Bell Creek and Cedar Creek Anticline properties, acquired as part of the Encore Merger.  Property acquisition costs for 2009 and prior were primarily related to CO2 tertiary potential at Conroe Field. Exploration and development costs shown as unevaluated properties are primarily associated with our tertiary oil fields that are under development but did not have proved reserves at December 31, 2012.  The most significant development costs incurred during 2012 and 2011 relate to development in preparation for upcoming CO2 floods at Bell Creek and Grieve fields. We have not yet recognized proved reserves in these fields.
Cost Incurred On Proved Reserves Transferred To Amortization Base	$ 431.1
Anticipated Timing of Inclusion of Costs in Amortization Calculation	We currently estimate that evaluation of most of these properties and the inclusion of their costs in the amortization base is expected to be completed within five years.