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Properties and Equipment, Net (Details 3) (USD $)
 12 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended
Dec. 31, 2012
Dec. 31, 2010
Dec. 31, 2011
Dec. 31, 2009
Dec. 31, 2010
Drilling and service equipment
Dec. 31, 2010
Oil and gas properties
Sep. 30, 2010
Oil and gas properties
Significant Unobservable Inputs (Level 3)
Dec. 31, 2010
Oil and gas properties
South Texas fields
item
Dec. 31, 2010
Colorado oil and gas properties
Properties and Equipment, Net                  
Minimum term of capitalization of exploratory well costs 1 year                
Capitalized exploratory well costs                  
Capitalized exploratory well costs that have been capitalized for a period of one year or less $ 10,390,000 $ 4,285,000 $ 5,328,000            
Balance at the end of the period 10,390,000 4,285,000 5,328,000 4,179,000          
Impairments                  
Impairment of oil and gas properties and other assets   40,903,000     5,100,000 35,800,000     5,800,000
Fair value of assets         $ 4,000,000     $ 15,400,000 $ 3,000,000
Number of fields with limited activity               2  
Risk adjusted discount rates (as a percent)             14.00%