Investments in Unconsolidated Joint Ventures - Summary of Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Schedule Of Equity Method Investments [Line Items]
Rental property, net	$ 214,741		$ 214,741		$ 221,827
Other assets	42,418		42,418		46,126
Total assets	257,159		257,159		267,953
Mortgage and notes payable	246,500		246,500		246,500
Other liabilities	16,843		16,843		30,321
Total liabilities	263,343		263,343		276,821
Equity	(6,184)		(6,184)		(8,868)
Total liabilities and equity	257,159		257,159		$ 267,953
712 Fifth Avenue [Member]
Schedule Of Equity Method Investments [Line Items]
Rental income	12,575		37,021
Tenant reimbursement income	1,059		3,795
Fee and other income	287		910
Total revenue	13,921		41,726
Operating	5,500		17,557
Depreciation and amortization	2,945		8,829
Total expenses	8,445		26,386
Operating income	5,476		15,340
Unrealized gain on interest rate swaps	74		2,094
Interest and other income, net	3		8
Interest and debt expense	(2,687)		(8,726)
Net income	$ 2,866		$ 8,716
712 Fifth Avenue [Member] | Predecessor [Member]
Schedule Of Equity Method Investments [Line Items]
Rental income		$ 11,920		$ 34,609
Tenant reimbursement income		1,116		3,385
Fee and other income		250		888
Total revenue		13,286		38,882
Operating		5,852		17,178
Depreciation and amortization		2,743		8,268
General and administrative		45		100
Total expenses		8,640		25,546
Operating income		4,646		13,336
Unrealized gain on interest rate swaps		2,692		5,337
Interest and debt expense		(3,650)		(10,936)
Net income		$ 3,688		$ 7,737