Annual report pursuant to Section 13 and 15(d)

Contingencies (Details)

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Contingencies (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 12 Months Ended
Sep. 30, 2010
Dec. 31, 2009
Dec. 31, 2011
Contingencies [Abstract]      
Liability Loss Contingency     $ 2.0
Allowable reductions of cash payments   (5.3)  
Notified disallowed amount in reductions taken by ONRR $ 4.7