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Additional Balance Sheet Details (Details 1) - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Receivables [Abstract]    
Trade accounts receivable, net $ 12,630 $ 11,643
Federal income tax receivable, net 2,987 9,037
Commodity derivative settlement receivables 675 2,390
Other receivables 2,026 3,900
Total $ 18,318 $ 26,970