Annual report pursuant to Section 13 and 15(d)

Fair Value Recurring Measurements (Details)

v3.6.0.2
Fair Value Recurring Measurements (Details) - Fair Value, Measurements, Recurring - USD ($)
$ in Thousands
Dec. 31, 2016
Dec. 31, 2015
Swaps | Interest Rate Swaps    
Liabilities:    
Derivative Liabilities $ 1,956 $ 2,176
Swaps | Commodity Contracts    
Assets:    
Derivative Assets   14,799
Forward Contracts | Commodity Contracts    
Liabilities:    
Derivative Liabilities 1,561 592
Forward Contracts | Fair Value Hedges    
Assets:    
Derivative Assets 14,777 33,797
Level 1 | Swaps | Interest Rate Swaps    
Liabilities:    
Derivative Liabilities 0 0
Level 1 | Swaps | Commodity Contracts    
Assets:    
Derivative Assets   0
Level 1 | Forward Contracts | Commodity Contracts    
Liabilities:    
Derivative Liabilities 1,561 592
Level 1 | Forward Contracts | Fair Value Hedges    
Assets:    
Derivative Assets 0 0
Level 2 | Swaps | Interest Rate Swaps    
Liabilities:    
Derivative Liabilities 1,956 2,176
Level 2 | Swaps | Commodity Contracts    
Assets:    
Derivative Assets   14,799
Level 2 | Forward Contracts | Commodity Contracts    
Liabilities:    
Derivative Liabilities 0 0
Level 2 | Forward Contracts | Fair Value Hedges    
Assets:    
Derivative Assets 14,777 33,797
Level 3 | Swaps | Interest Rate Swaps    
Liabilities:    
Derivative Liabilities 0 0
Level 3 | Swaps | Commodity Contracts    
Assets:    
Derivative Assets   0
Level 3 | Forward Contracts | Commodity Contracts    
Liabilities:    
Derivative Liabilities 0 0
Level 3 | Forward Contracts | Fair Value Hedges    
Assets:    
Derivative Assets $ 0 $ 0