Investments in Unconsolidated Real Estate Partnerships (Details Textual) (USD $)	12 Months Ended
Dec. 31, 2011 Property	Dec. 31, 2010 Property PartnershipUnit	Dec. 31, 2009 Property
Investments in Unconsolidated Real Estate Partnerships (Textual) [Abstract]
Number of properties owned by unconsolidated real estate partnerships	123	173	77
Number of investment partnerships consolidated upon accounting change		18
Aggregate investment in unconsolidated partnerships	$ 47,790,000	$ 59,282,000
Excess of equity method investment aggregate cost over share of underlying historical partners deficit	$ 46,500,000	$ 63,000,000
Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Range of ownership interests in unconsolidated real estate partnerships	50.00%	50.00%
Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Range of ownership interests in unconsolidated real estate partnerships	1.00%	1.00%

The item represents the difference, if any, between the amount at which an investment accounted for under the equity method of accounting is carried (reported) on the balance sheet and the amount of underlying equity in net assets the reporting Entity has in the investee. A difference can arise between the carrying value of the equity method investment and the value of the Entity's amount of underlying equity in net assets of the investee, for example, from appreciation of certain assets which is not recognized in earnings, but is recognized in other comprehensive income (a separate component of shareholders' equity) by the investee.

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

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