Derivative Instruments (Details 1) (Commodity Contract [Member], Designated as Hedging Instrument, USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Hedge Asset [Member]
Derivatives, Fair Value [Line Items]
Derivative asset	$ 186	$ 521
Hedge Liability [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	$ (3,840)	$ (1,617)