Derivative and Other Fair Value Instruments (Details 3) (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Schedule of Location of Fair Value/Cash flow Hedges on Statement of Operations
Effective Portion - Amount of Gain/ (Loss) Recognized in OCI on Derivative	$ (130,367)	$ (123,472)
Effective Portion - Amount of Gain/ (Loss) Reclassified from Accumulated OCI into Income	(2,842)	(2,379)
Ineffective Portion - Amount of Gain/ (Loss) Reclassified from Accumulated OCI into Income	0
Forward Starting Swaps/Treasury Locks [Member]
Schedule of Location of Fair Value/Cash flow Hedges on Statement of Operations
Effective Portion - Amount of Gain/ (Loss) Recognized in OCI on Derivative	(131,689)	(124,908)
Ineffective Portion - Amount of Gain/ (Loss) Reclassified from Accumulated OCI into Income	0
Forward Starting Swaps/Treasury Locks [Member] | Interest Expense [Member]
Schedule of Location of Fair Value/Cash flow Hedges on Statement of Operations
Effective Portion - Amount of Gain/ (Loss) Reclassified from Accumulated OCI into Income	(2,842)	(2,379)
Development Interest Rate Swaps/Caps [Member]
Schedule of Location of Fair Value/Cash flow Hedges on Statement of Operations
Effective Portion - Amount of Gain/ (Loss) Recognized in OCI on Derivative	1,322	1,436
Development Interest Rate Swaps/Caps [Member] | Interest Expense [Member]
Schedule of Location of Fair Value/Cash flow Hedges on Statement of Operations
Effective Portion - Amount of Gain/ (Loss) Reclassified from Accumulated OCI into Income	$ 0