Investments in Partially Owned Entities (Details Textuals) (USD $)	6 Months Ended	12 Months Ended
Jun. 30, 2011	Dec. 31, 2010
Noncontrolling Interest [Line Items]
Partially Owned Properties	$ 3,295,000	$ 7,991,000
Significant Acquisitions and Disposals [Line Items]
Units - acquired	2,069
Properties - acquired	7
Investments In Partially Owned Entities (Textuals) [Abstract]
14.0 million will become recourse	14,000,000
Partner's acquired 80% equity interest		80.00%
Partner's payment to Acquire Additional Interest in unconsolidated properties		11,700,000
VIE ownership	50.00%
Total project cost		78,200,000
Estimated remaining funding obligation		2,400,000
Consolidated Other [Member]
Noncontrolling Interest [Line Items]
Partially Owned Properties	$ 3,300,000
Institutional Partner [Member]
Significant Acquisitions and Disposals [Line Items]
Interest retained		20.00%

Total number of rental property or properties acquired from unaffiliated third parties during the period.

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- Definition

Mortgage debt on a development project that will not be secured by collateral upon completion of the project.

+ Details

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- Definition

Represents the remaining amount of capital to be funded to a joint venture by the Company. This will complete the Company's equity interest in the joint venture.

+ Details

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- Definition

Represents co-investments with minority partners in various consolidated partnerships and development joint venture partners.

+ Details

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- Definition

Represents the ownership interest sold to a third party as part of the formation of a joint venture.

+ Details

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- Definition

Carrying amount of equity interests owned by noncontrolling partners in partially owned properties.

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- Definition

The cash inflow to the Company associated with a partner's purchase of or advances to an equity method investment, which is an investment in a joint venture or an entity.

+ Details

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- Definition

Represents total project cost for the development of a land parcel to a residential apartment community.

+ Details

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- Definition

Total number of units associated with the property or properties acquired from unaffiliated third parties during the period.

+ Details

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- Definition

Percentage of the VIE that is legally owned by the Company's joint venture partners. In general, a VIE is a corporation, partnership, trust, or any other legal structure used for business purposes that either (a) does not have equity investors with voting rights or (b) has equity investors that do not provide sufficient financial resources for the entity to support its activities. A VIE often holds financial assets, including loans or receivables, real estate or other property. A VIE may be essentially passive or it may engage in research and development or other activities on behalf of another company.

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 18
-Subparagraph f
-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
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 18
-Paragraph 20
-Subparagraph a (1)
-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 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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