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Leases (Narratives) (Details) | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jan. 31, 2016 USD ($) ft² leases | Oct. 31, 2014 ft² | Dec. 31, 2015 USD ($) options | Sep. 30, 2015 USD ($) | Jun. 30, 2015 USD ($) | Mar. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Sep. 30, 2014 USD ($) | Jun. 30, 2014 USD ($) | Mar. 31, 2014 USD ($) | Dec. 31, 2015 USD ($) options | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($)
as Lessor [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Additional Rent Based on Percentage of Tenant's sales |  |  |  |  |  |  |  |  |  |  | $ 94,000 | $ 108,000 | $ 416,000
Real estate revenue, net (in dollars) |  |  | $ 52,819,000 | $ 52,414,000 | $ 50,646,000 | $ 52,036,000 | $ 51,286,000 | $ 50,077,000 | $ 49,983,000 | $ 49,468,000 | 207,915,000 | 200,814,000 | 196,459,000
Lessee [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Rent expense |  |  |  |  |  |  |  |  |  |  | 746,000 | 746,000 | 746,000
Leasing Fees [Member] | Vornado [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
as Lessor [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Fees owed (in US dollars) |  |  | $ 2,473,000 |  |  |  |  |  |  |  | $ 2,473,000 |  |
Subsequent Event [Member] | Leasing Fees [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
as Lessor [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Fees owed (in US dollars) | $ 8,916,000 |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Member] | Leasing Fees [Member] | Vornado [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
as Lessor [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Fees owed (in US dollars) | 1,716,000 |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Member] | Leasing Fees [Member] | Third party Broker [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
as Lessor [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Fees owed (in US dollars) | $ 7,200,000 |  |  |  |  |  |  |  |  |  |  |  |
Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Leases Lease Terms [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Lease term range as Lessor |  |  |  |  |  |  |  |  |  |  | 5 years |  |
Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Leases Lease Terms [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Lease term range as Lessor |  |  |  |  |  |  |  |  |  |  | 25 years |  |
Customer Concentration Risk [Member] | Bloomberg [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
as Lessor [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage Of Minimum Revenue Threshold Contributed By One Tenant (in percentage) |  |  |  |  |  |  |  |  |  |  | 10.00% |  |
Customer Concentration Risk [Member] | Bloomberg [Member] | Sales Revenue Services Net [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
as Lessor [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Real estate revenue, net (in dollars) |  |  |  |  |  |  |  |  |  |  | $ 94,468,000 | $ 91,109,000 | $ 88,164,000
Percentage Rent Contributed By Tenant |  |  |  |  |  |  |  |  |  |  | 45.00% | 45.00% | 45.00%
Flushing Property [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Lessee [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Leases Expiration Date |  |  |  |  |  |  |  |  |  |  | 2027 |  |
Flushing Property [Member] | Ten Year Extension Option [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Lessee [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Number Of Extension Options | options |  |  | 1 |  |  |  |  |  |  |  | 1 |  |
Lease Extension Period Maximum |  |  |  |  |  |  |  |  |  |  | 10 years |  |
731 Lexington Avenue [Member] | Bloomberg [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
as Lessor [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Area of property (in square feet) | ft² |  | 192,000 |  |  |  |  |  |  |  |  |  |  |
Lease renewal term |  | 5 years |  |  |  |  |  |  |  |  |  |  |
Lessee [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Leases Expiration Date |  | December 2015 |  |  |  |  |  |  |  |  |  |  |
731 Lexington Avenue [Member] | Bloomberg [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
as Lessor [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Area of property (in square feet) | ft² | 697,000 |  |  |  |  |  |  |  |  |  |  |  |
Lease renewal term | 10 years |  |  |  |  |  |  |  |  |  |  |  |
Letter of credit issued by customer | $ 200,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Lessee [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Leases Expiration Date | February 2029 |  |  |  |  |  |  |  |  |  |  |  |
731 Lexington Avenue [Member] | Ten Year Extension Option [Member] | Bloomberg [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
as Lessor [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Number Of Leases | leases | 1 |  |  |  |  |  |  |  |  |  |  |  |

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- Definition Term of the lessee's leasing arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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