Investments in Unconsolidated Joint Ventures - Summary of Financial Information (Details) - 712 Fifth Avenue [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Schedule Of Equity Method Investments [Line Items]
Rental property, net	$ 212,052		$ 214,139
Other assets	42,064		41,337
Total assets	254,116		255,476
Notes and mortgages payable, net	245,684		245,582
Other liabilities	13,696		15,000
Total liabilities	259,380		260,582
Equity	(5,264)		(5,106)
Total liabilities and equity	254,116		$ 255,476
Rental income	12,678	$ 12,054
Tenant reimbursement income	1,116	1,361
Fee and other income	518	279
Total revenues	14,312	13,694
Operating	5,617	6,228
Depreciation and amortization	3,008	2,930
Total expenses	8,625	9,158
Operating income	5,687	4,536
Unrealized gain on interest rate swaps		771
Interest and other income, net	14	2
Interest and debt expense	(2,748)	(3,428)
Net income	$ 2,953	$ 1,881