Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments and Hedging Transactions (Realized Gain (Loss)) (Details)

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Derivative Instruments and Hedging Transactions (Realized Gain (Loss)) (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Derivative [Line Items]        
Gains (losses) on derivative instruments: $ 7,169 $ (12,625) $ (7,964) $ 2,019
Futures Commodity And Forwards Contracts And Open Purchase And Sale Commitments        
Derivative [Line Items]        
Unrealized gains (losses) on open future commodity and forward contracts and open sale and purchase commitments, net 8,408 (22,260) (11,490) (10,003)
Commodity Contract        
Derivative [Line Items]        
Realized (losses) gains on future commodity contracts, net $ (1,239) $ 9,635 $ 3,526 $ 12,022