Quarterly report pursuant to Section 13 or 15(d)

Schedule of Derivative Instruments, Gain (Loss) in Statements of Financial Performance (Details)

v3.7.0.1
Schedule of Derivative Instruments, Gain (Loss) in Statements of Financial Performance (Details) - Not Designated as Hedging Instrument, Economic Hedge - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Derivative Instruments, Gain (Loss)        
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net $ 1,323 $ 823 $ 3,479 $ 6,197
Cost of Sales | Forward Contracts | Commodity Contracts        
Derivative Instruments, Gain (Loss)        
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net $ 1,323 $ 823 $ 3,479 $ 6,197