Derivative Financial Instruments Derivative Gains (losses) table (Details) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Oct. 07, 2010	Jun. 02, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				4.80%	6.00%
Debt Instrument, Interest Rate, Effective Percentage				6.26%	7.67%
Notional Amount of Interest Rate Derivatives			$ 290,700,000	$ 140,700,000
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(9,467,000)	(5,575,000)	(2,305,000)
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	18,000	(36,556,000)	38,645,000
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	$ (54,000)	$ 1,419,000	$ (3,294,000)