Derivatives (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Derivative Liabilities Noncurrent	$ 7
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets, Current	1,568	151
Derivative Assets, Noncurrent	125	0
Derivative Liabilities, Current	0	(702)
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets, Current	5,112	2,716
Derivative Assets, Noncurrent	1,479	0
Derivative Liabilities, Current	(2,839)	(4,885)
Derivative Liabilities Noncurrent	(7)	0
Total [Member]
Derivatives, Fair Value [Line Items]
Net Fair value of derivatives	$ 5,438	$ (2,720)