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	Sep. 30, 2016	Dec. 31, 2015
Offsetting Assets and Liabilities [Line Items]
Derivative Assets	$ 3,559	$ 19,943
Derivative Liabilities	(10,722)
Current assets - Fair value of derivatives [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative asset, fair value, gross asset	3,591	19,943
Derivative asset, fair value, gross liability	(89)
Derivative Assets	3,502	$ 19,943
Long-term assets: Fair value of derivatives [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative asset, fair value, gross asset	57
Derivative Assets	57
Current liabilities - Fair value of derivatives [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative liability, fair value, gross liability	(7,875)
Derivative liability, fair value, gross asset	89
Derivative Liabilities	(7,786)
Non-current liabilities - Fair value of derivatives [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative liability, fair value, gross liability	(2,936)
Derivative Liabilities	$ (2,936)