Organization (Details) (USD $)	12 Months Ended
Organization (Details) (USD $)	Dec. 31, 2014 Segment property	Dec. 31, 2013	Dec. 31, 2001 acre
Operating Properties [Abstract]
Number of properties in greater New York City metropolitan area (in property)	6us-gaap_NumberOfRealEstateProperties
Development and construction in progress	$ 75,289,000us-gaap_DevelopmentInProcess	$ 4,924,000us-gaap_DevelopmentInProcess
Number Of Operating Segments	1us-gaap_NumberOfOperatingSegments
731 Lexington Avenue [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	1,307,000
731 Lexington Avenue [Member] \| Office Space [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	885,000
731 Lexington Avenue [Member] \| Office Space [Member] \| Tenant Occupant [Member] \| Bloomberg [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	885,000
731 Lexington Avenue [Member] \| Retail Space [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	174,000
731 Lexington Avenue [Member] \| Retail Space [Member] \| Tenant Occupant [Member] \| Container Store [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	34,000
731 Lexington Avenue [Member] \| Retail Space [Member] \| Tenant Occupant [Member] \| Hennes Mauritz [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	27,000
731 Lexington Avenue [Member] \| Retail Space [Member] \| Tenant Occupant [Member] \| Home Depot [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	83,000
731 Lexington Avenue [Member] \| Residential Space [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Number of units in real estate property (in units)	105
Area of property (in square feet)	248,000
Rego Park I [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	343,000
Rego Park I [Member] \| Tenant Occupant [Member] \| Burlington Coat Factory [Member] \| Anchor [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	50,000
Rego Park I [Member] \| Tenant Occupant [Member] \| Marshalls [Member] \| Anchor [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	36,000
Rego Park I [Member] \| Tenant Occupant [Member] \| Bed Bath Beyond [Member] \| Anchor [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	46,000
Rego Park I [Member] \| Tenant Occupant [Member] \| Sears [Member] \| Anchor [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	195,000
Rego Park II [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	609,000
Rego Park II [Member] \| Tenant Occupant [Member] \| Toys R Us/ Babys R Us [Member] \| Anchor [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	47,000
Rego Park II [Member] \| Tenant Occupant [Member] \| Kohls [Member] \| Anchor [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	133,000
Rego Park II [Member] \| Tenant Occupant [Member] \| Century 21 [Member] \| Anchor [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	135,000
Rego Park II [Member] \| Tenant Occupant [Member] \| Costco [Member] \| Anchor [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	145,000
Rego Park II [Member] \| Apartment Tower [Member] \| Property Under Development [Member]
Operating Properties [Abstract]
Number of units in real estate property (in units)	312
Area of property (in square feet)	255,000
Estimated Date Of Completion	2015
Development and construction in progress	73,327,000
Rego Park II [Member] \| Apartment Tower [Member] \| Maximum [Member] \| Property Under Development [Member]
Operating Properties [Abstract]
Estimated Budgeted Cost	$ 125,000,000
Paramus [Member] \| Tenant Occupant [Member] \| Ikea [Member]
Operating Properties [Abstract]
Area Of Land (in acre)			30.3
Paramus [Member] \| Tenant Occupant [Member] \| Ikea [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area Of Land (in acre)	30.3
Flushing [Member] \| Tenant Occupant [Member] \| New World Mall Llc [Member] \| Operating Property [Member]
Operating Properties [Abstract]
Area of property (in square feet)	167,000
Rego Park III [Member] \| Property To Be Developed [Member]
Operating Properties [Abstract]
Area Of Land (in acre)	3.2