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 - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Derivative Instruments, Gain (Loss)    
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net $ (871) $ 5,579
Cost of Sales | Forward Contracts | Commodity Contracts    
Derivative Instruments, Gain (Loss)    
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net (871) 5,213
Cost of Sales | Swaps | Commodity Contracts    
Derivative Instruments, Gain (Loss)    
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net $ 0 $ 366