|**Long-Term Debt (Tables)**                               | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
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|**Long-term Debt, Unclassified [Abstract]**               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Schedule of Long-term Debt Instruments [Table Text Block] | Long-term debt consisted of the following:September 30, 2012December 31, 2011(in thousands)Senior notes:3.25% Convertible senior notes due 2016:Principal amount$115,000$115,000Unamortized discount(14,546)(17,079)3.25% Convertible senior notes due 2016, net of discount100,45497,92112% Senior notes due 2018:Principal amount203,000203,000Unamortized discount(1,546)(1,764)12% Senior notes due 2018, net of discount201,454201,236Total senior notes301,908299,157Credit facilities:Corporate307,000209,000PDCM25,00024,000Total credit facilities332,000233,000Total long-term debt$633,908$532,157
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|                                                          | September 30, 2012                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|                                                          | (in thousands)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|Senior notes:                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|3.25% Convertible senior notes due 2016:                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Principal amount                                          | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|Unamortized discount                                      | (14,546                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|3.25% Convertible senior notes due 2016, net of discount  | 100,454                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|12% Senior notes due 2018:                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Principal amount                                          | 203,000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Unamortized discount                                      | (1,546                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|12% Senior notes due 2018, net of discount                | 201,454                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Total senior notes                                        | 301,908                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Credit facilities:                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Corporate                                                 | 307,000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|PDCM                                                      | 25,000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Total credit facilities                                   | 332,000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Total long-term debt                                      | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
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