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Asset Retirement Obligation - Change in Asset Retirement Obligation (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2014
Asset Retirement Obligation Disclosure [Abstract]  
Asset retirement obligation at beginning of period $ 2
Additions during the period 0
Revisions of estimates 0
Accretion expense 0
Asset retirement obligation at end of period $ 2 [1]
[1] This is a recurring Level 3 fair value measurement. See Note 7 - "Fair Value Measurements" for further discussions of Level 3 valuation definitions.