Fair Value Measurements (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Trust's financial assets for which the fair value option was elected
Financial instruments at fair value	$ 12,231	$ 19,705
Securities carried at fair value [Member] \| REIT common shares [Member]
Trust's financial assets for which the fair value option was elected
Financial instruments at fair value	12,220	19,694
Loan securities carried at fair value [Member]
Trust's financial assets for which the fair value option was elected
Financial instruments at fair value	$ 11	$ 11

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant