Investments in Unconsolidated Joint Ventures - Summary of Financial Information (Details) - 712 Fifth Avenue [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Schedule Of Equity Method Investments [Line Items]
Rental property, net	$ 208,578		$ 208,578		$ 214,139
Other assets	42,534		42,534		41,337
Total assets	251,112		251,112		255,476
Notes and mortgages payable, net	245,888		245,888		245,582
Other liabilities	11,324		11,324		15,000
Total liabilities	257,212		257,212		260,582
Equity	(6,100)		(6,100)		(5,106)
Total liabilities and equity	251,112		251,112		$ 255,476
Rental income	12,107	$ 12,575	37,501	$ 37,021
Tenant reimbursement income	1,342	1,059	3,351	3,795
Fee and other income	418	287	1,613	910
Total revenues	13,867	13,921	42,465	41,726
Operating	6,081	5,500	17,073	17,557
Depreciation and amortization	3,193	2,945	9,244	8,829
Total expenses	9,274	8,445	26,317	26,386
Operating income	4,593	5,476	16,148	15,340
Interest and other income, net	16	3	49	8
Interest and debt expense	(2,787)	(2,687)	(8,287)	(8,726)
Unrealized gain on interest rate swaps	1,722	74	2,556	2,094
Net income	$ 3,544	$ 2,866	$ 10,466	$ 8,716