Related-Party Transactions - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013
FUR Advisors [Member]
Related Party Transaction [Line Items]
Percentage of Equity contributions	1.50%
Percentage of Equity contributions by unaffiliated third parties	0.25%
Payable to related parties included in related party fees payable	$ 2,309,000
Winthrop Management [Member]
Related Party Transaction [Line Items]
Payable to related parties included in related party fees payable	$ 383,000