Loans Receivable - Additional Information (Detail)		1 Months Ended		7 Months Ended	9 Months Ended	12 Months Ended
	Feb. 05, 2015 USD ($)	Jul. 31, 2014 USD ($) Loans	Aug. 31, 2013 USD ($)	Jul. 31, 2014 USD ($) Loans	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Oct. 09, 2015 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, accrued interest					$ 27,000	$ 218,000
Weighted average coupon rate on loans receivable					8.05%	10.55%
Weighted average yield to maturity					13.73%	12.78%
Provision for loan loss		$ 0		$ 0
Number of non-performing loans with past due payments | Loans		1		1
Period for the return of assets					2 years
Annual interest rate			15.00%
Edens Center and Norridge Commons [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal payment of loans	$ 15,275,000
Outstanding principal balance on loan receivable					$ 97,000
Loan participation interest percentage					30.00%
Minimum value of properties for entitlement to loan participation interest					$ 115,000,000
Description of Trust's participation interest in loan					Upon satisfaction of the loan, the Trust was entitled to a participation interest equal to 30% of the value of both of the properties which collateralized the loan in excess of $115,000,000.
Edens Center and Norridge Commons [Member] | Subsequent Event [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivable							$ 3,100,000
Lender LP [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Secured financing receivable			$ 30,000,000
Elad Canada Ltd [Member] | Lender LP [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Rate of interest for acquisition			50.00%
Secured Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income		$ 324,000		$ 2,215,000