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

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 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

Reference 3: 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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Investments in Unconsolidated Real Estate Partnerships (Details Textual) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012 Property	Dec. 31, 2011 Property	Dec. 31, 2010 Property
Schedule of Equity Method Investments [Line Items]
Number of properties owned by unconsolidated real estate partnerships	22	123	173
Aggregate investment in unconsolidated partnerships	$ 18.7	$ 47.8
Excess of equity method investment aggregate cost over share of underlying historical partners deficit	$ 6.9	$ 46.5
Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Range of ownership interests in unconsolidated real estate partnerships	67.00%
Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Range of ownership interests in unconsolidated real estate partnerships	5.00%