Annual report pursuant to Section 13 and 15(d)

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

v3.6.0.2
Derivative Instruments and Hedging Activities (Schedule of Derivative Instruments in Statement of Financial Position, Fair Value) (Details) - USD ($)
Dec. 31, 2016
Dec. 31, 2015
Offsetting Assets and Liabilities [Line Items]    
Derivative Assets $ 103,000 $ 19,943,000
Derivative Liabilities (18,296,000)  
Not Designated as Hedging Instrument [Member]    
Offsetting Assets and Liabilities [Line Items]    
Derivative Assets 103,000 19,943,000
Derivative Liabilities (18,296,000)  
Not Designated as Hedging Instrument [Member] | Current assets: Fair value of hedging contracts [Member]    
Offsetting Assets and Liabilities [Line Items]    
Derivative asset, fair value, gross asset 1,836,000 19,943,000
Derivative asset, fair value, gross liability (1,733,000)  
Derivative Assets 103,000 $ 19,943,000
Not Designated as Hedging Instrument [Member] | Current liabilities: Fair value of hedging contracts [Member]    
Offsetting Assets and Liabilities [Line Items]    
Derivative liability, fair value, gross liability (20,001,000)  
Derivative liability, fair value, gross asset 1,733,000  
Derivative Liabilities (18,268,000)  
Not Designated as Hedging Instrument [Member] | Non-current liabilities - Fair value of derivatives [Member]    
Offsetting Assets and Liabilities [Line Items]    
Derivative liability, fair value, gross liability (28,000)  
Derivative Liabilities $ (28,000)