Property (Schedule Of Property) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Property
Land	$ 956,449	$ 925,497
Land held for development	157,179	170,213
Land under development	15,418	22,967
Buildings and improvements	3,658,921	3,610,889
Construction in-progress	39,407	48,228
Total	$ 4,827,374	$ 4,777,794

Gross amount, at the balance sheet date, of long-lived assets under construction that include construction costs to date on capital projects that have not been completed and assets being constructed that are not ready to be placed into service.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 12
-Paragraph 5
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
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Carrying amount as of the balance sheet date, net of valuation allowances and impairment losses, of costs of land expected to be developed in the near term plus capitalized costs of development, for purposes of selling completed units to home buyers or commercial or industrial entities..

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 6
-Subparagraph a
-Article 5

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-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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Aggregate of the carrying amounts as of the balance sheet date of investments in building and building improvements.

+ References

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-Topic 944
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-Subparagraph (SX 210.7-03.1(d))
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Carrying amount as of the balance sheet date of real estate held for productive use. This excludes land held for sale.

+ References

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-Name Accounting Standards Codification
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Carrying amount of land available for development.

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-Article 7
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Represents a total which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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