Fair Value of Financial Instruments (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Derivatives Designated as Cash Flow Hedges [Member]
Gains and losses on derivative instruments in the consolidated statement of operations
Amount of Gain (Loss) Recognized in Other Comprehensive Income on Derivative (Effective Portion)	$ 4,643	$ (1,795)	$ (7,208)
Amount of (Loss) Gain Reclassified from Other Comprehensive Loss into Income (Effective Portion)	(4,626)	(692)	(4,198)
Amount of Gain (Loss) Recognized in Income on Derivative (Ineffective Portion)	(367)	47	(458)
Other Income (Expense) [Member] | Derivatives not Designated as Hedging Instruments [Member]
Gains and losses on derivative instruments in the consolidated statement of operations
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 212	$ (758)	$ 1,997