Equity Investments - Additional Information (Detail)						1 Months Ended		6 Months Ended	7 Months Ended	9 Months Ended
	Oct. 09, 2015 USD ($) Property	Jul. 01, 2015 USD ($)	Jun. 25, 2015 USD ($) Assets SecurityLoan	Jun. 01, 2015 USD ($)	Jan. 02, 2015 USD ($)	Oct. 31, 2015 USD ($)	May. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)	Jul. 31, 2014 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of equity investments				$ 82,471,000					$ 200,000
Distributions received								$ 4,959,000	$ 705,000
Subsequent Event [Member] | Edens Center and Norridge Commons [Member]
Schedule of Equity Method Investments [Line Items]
Aggregate price in sale of general partnership interest	$ 493,000
Number of properties sold | Property	2
Vintage Housing Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Additional contribution in equity investments					$ 5,645,000
Liquidation value of investment											$ 82,928,000
Concord Debt Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Distributions received							$ 20,173,000
701 Seventh WRT Investor LLC [Member]
Schedule of Equity Method Investments [Line Items]
Additional capital contributions										$ 5,258,000
Capital contributions										$ 111,882,000
701 Seventh WRT Investor LLC [Member] | Subsequent Event [Member]
Schedule of Equity Method Investments [Line Items]
Additional capital contributions						$ 1,039,000
Capital contributions						$ 112,921,000
CDH CDO LLC [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of equity investments			$ 54,122,000
Number of bond assets sold | Assets			4
Number of loan asset sold | SecurityLoan			1
Amount received from the venture		$ 6,200,000