Quarterly report pursuant to Section 13 or 15(d)

Asset Retirement Obligations (Details)

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Asset Retirement Obligations (Details) (USD $)
In Thousands, unless otherwise specified
9 Months Ended
Sep. 30, 2013
Asset Retirement Obligations  
Asset retirement obligations - beginning of period $ 10,552
Obligations incurred 69
Accretion expense 797
Asset retirement obligations - end of period $ 11,418