Quarterly report pursuant to Section 13 or 15(d)

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

v3.8.0.1
Derivative Instruments and Hedging Transactions (Realized Gain (Loss)) (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Derivative [Line Items]        
Gains (losses) on derivative instruments: $ (12,625) $ (22,900) $ 2,019 $ (19,009)
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 (22,260) (52,983) (10,003) (34,833)
Commodity Contract        
Derivative [Line Items]        
Realized (losses) gains on future commodity contracts, net $ 9,635 $ 30,083 $ 12,022 $ 15,824