Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments and Hedging Activities (Schedule of Derivative Instruments in Statement of Financial Position, Fair Value) (Details)

v3.5.0.2
Derivative Instruments and Hedging Activities (Schedule of Derivative Instruments in Statement of Financial Position, Fair Value) (Details) - Not Designated as Hedging Instrument [Member] - USD ($)
$ in Thousands
Jun. 30, 2016
Dec. 31, 2015
Offsetting Assets and Liabilities [Line Items]    
Derivative Assets $ 5,597 $ 19,943
Derivative Liabilities (13,804)  
Current assets - Fair value of derivatives [Member]    
Offsetting Assets and Liabilities [Line Items]    
Derivative asset, fair value, gross asset 5,655 19,943
Derivative asset, fair value, gross liability (118)  
Derivative Assets 5,537 $ 19,943
Long-term assets: Fair value of derivatives [Member]    
Offsetting Assets and Liabilities [Line Items]    
Derivative asset, fair value, gross asset 60  
Derivative Assets 60  
Current liabilities - Fair value of derivatives [Member]    
Offsetting Assets and Liabilities [Line Items]    
Derivative liability, fair value, gross liability (7,609)  
Derivative liability, fair value, gross asset 118  
Derivative Liabilities (7,491)  
Non-current liabilities - Fair value of derivatives [Member]    
Offsetting Assets and Liabilities [Line Items]    
Derivative liability, fair value, gross liability (6,313)  
Derivative Liabilities $ (6,313)