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FAIR VALUE OF FINANCIAL INSTRUMENTS (Details 2) - Recurring - USD ($)
$ in Thousands
Sep. 30, 2015
Dec. 31, 2014
Assets    
Restricted investments in US Treasury Bonds - available for sale, at fair value $ 1,474 $ 1,422
Commodity derivatives 7,530 4,005
Level 1    
Assets    
Restricted investments in US Treasury Bonds - available for sale, at fair value 1,474 1,422
Level 2    
Assets    
Commodity derivatives $ 7,530 $ 4,005