Mortgage Notes Payable (Schedule of Mortgage Notes Payable) (Details)		3 Months Ended
		Mar. 31, 2016 USD ($) mortgage property	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Outstanding Loan Amount		$ 369,395,000
Mortgage notes payable, net of deferred financing costs		363,085,000	$ 381,443,000
1440 Broadway
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 325,000,000
Mortgages
Debt Instrument [Line Items]
Encumbered Properties | property		4
Outstanding Loan Amount		$ 369,395,000	388,436,000
Effective Interest Rate	[1]	4.00%
Less: deferred financing costs, net		$ (6,310,000)	(6,993,000)
Mortgages | Design Center
Debt Instrument [Line Items]
Encumbered Properties | property		1
Outstanding Loan Amount		$ 19,695,000	19,798,000
Effective Interest Rate		4.40%
Mortgages | 1100 Kings Highway
Debt Instrument [Line Items]
Encumbered Properties | property		1
Outstanding Loan Amount		$ 20,200,000	20,200,000
Effective Interest Rate		3.40%
Mortgages | 256 West 38th Street
Debt Instrument [Line Items]
Encumbered Properties | property		1
Outstanding Loan Amount		$ 24,500,000	24,500,000
Effective Interest Rate		3.10%
Mortgages | 1440 Broadway
Debt Instrument [Line Items]
Encumbered Properties | property	[2]	1
Outstanding Loan Amount	[2]	$ 305,000,000	305,000,000
Effective Interest Rate	[2]	4.00%
Additional available borrowing capacity		$ 20,000,000
Mortgages | Foot Locker
Debt Instrument [Line Items]
Encumbered Properties | property	[3]
Outstanding Loan Amount	[3]	$ 0	3,250,000
Effective Interest Rate	[3]
Mortgages | Duane Reade
Debt Instrument [Line Items]
Encumbered Properties | property	[3]
Outstanding Loan Amount	[3]	$ 0	8,400,000
Effective Interest Rate	[3]
Mortgages | 1623 Kings Highway
Debt Instrument [Line Items]
Encumbered Properties | property	[3]
Outstanding Loan Amount	[3]	$ 0	$ 7,288,000
Effective Interest Rate	[3]
Held-for-sale Property
Debt Instrument [Line Items]
Number of mortgages repaid | mortgage		3

[1] Calculated on a weighted average basis for all mortgages outstanding as of March 31, 2016.

[2] Total commitments of $325.0 million; additional $20.0 million available, subject to lender approval, to fund certain tenant allowances, capital expenditures and leasing costs.

[3] During the three months ended March 31, 2016, the Company repaid three mortgage notes payable as a result of the sales of Duane Reade, 1623 Kings Highway and Foot Locker.