Fair Value of Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Assets and liabilities measured at fair value on a recurring basis
Total derivative (Assets) Liabilities	$ (5,869)	$ 3,977
Fair Value Measurements Recurring [Member]
Assets and liabilities measured at fair value on a recurring basis
Total derivative (Assets) Liabilities	(5,869)	3,977
Fair Value Measurements Recurring [Member] | Quoted Prices in Active Markets for Identical Assets Level 1 [Member]
Assets and liabilities measured at fair value on a recurring basis
Total derivative (Assets) Liabilities	0	0
Fair Value Measurements Recurring [Member] | Significant Other Observable Inputs Level 2 [Member]
Assets and liabilities measured at fair value on a recurring basis
Total derivative (Assets) Liabilities	(5,869)	3,977
Fair Value Measurements Recurring [Member] | Significant Unobservable Inputs Level 3 [Member]
Assets and liabilities measured at fair value on a recurring basis
Total derivative (Assets) Liabilities	$ 0	$ 0