Annual report pursuant to Section 13 and 15(d)

Acquisitions (Details)

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Acquisitions (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended 0 Months Ended 1 Months Ended
Dec. 31, 2011
Dec. 31, 2011
Utica Shale [Member]
A
Jun. 15, 2010
Niobrara Formation Of Colorado [Member]
May 31, 2010
Permian Basin [Member]
May 31, 2010
Permian And Niobrara [Member]
Affiliates participation ratio 50/50        
Gas and Oil Acreage, Undeveloped, Gross   98,000   4,979  
Gas and Oil Acreage, Undeveloped, Net   49,000   2,489  
Equity offered for the payment of acquisition, shares   6.2     1.7
Equity offered for the payment of acquisition, values   $ 179.0     $ 21.6
Commitments to increase acreage position   125,000      
Commitments to increase acreage position, net   62,500      
Cash price of ownership interest   118.1   7.6  
Adjusted purchase price of acquired assets     $ 7.7    
Percentage of interest acquired       50.00%