Real Estate And Accumulated Depreciation (Changes In Real Estate Assets) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010		Dec. 31, 2009
Real Estate And Accumulated Depreciation [Abstract]
Balance, beginning of year	$ 4,377,730	$ 3,915,979		$ 3,872,390
New property acquisitions	511,308	346,770
Additions	160,109	146,645		149,134
Disposals associated with deconsolidation of the VIE		(27,464)	[1]
Disposals and retirements	(6,823)	(4,200)		(105,545)
Balance, end of year	$ 5,042,324	$ 4,377,730		$ 3,915,979

[1] Refer to Note 4 for discussion of the Company's sale of its general partnership interest in the VIE and the resulting deconsolidation of the VIE.