Derivatives and Hedging Activities (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Derivative Instruments, Gain (Loss) [Line Items]
Non-cash loss on derivatives and hedging instruments	$ 0	$ 2,893
Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Non-cash loss on derivatives and hedging instruments	$ 0	$ 2,900	$ 0