Organization (Details) ft² in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) ft² unit segment property extension
Operating Properties
Number of properties | property	6
Number of segments | segment	1
731 Lexington Avenue
Operating Properties
Area of property (in square feet)	1,079
731 Lexington Avenue | Office space
Operating Properties
Area of property (in square feet)	939
731 Lexington Avenue | Retail space
Operating Properties
Area of property (in square feet)	140
731 Lexington Avenue | Retail space | Tenant Occupant | Home Depot
Operating Properties
Area of property (in square feet)	83
Rego Park I | Anchor
Operating Properties
Area of property (in square feet)	338
Rego Park I | Anchor | IKEA
Operating Properties
Area of property (in square feet)	112
Rego Park I | Anchor | IKEA | Operating property
Operating Properties
Payment for termination of lease | $	$ 10
Rego Park I | Anchor | Burlington Coat Factory
Operating Properties
Area of property (in square feet)	50
Rego Park I | Anchor | Bed Bath and Beyond
Operating Properties
Area of property (in square feet)	46
Rego Park I | Anchor | Marshalls
Operating Properties
Area of property (in square feet)	36
Rego Park II | Anchor
Operating Properties
Area of property (in square feet)	615
Rego Park II | Anchor | Costco
Operating Properties
Area of property (in square feet)	145
Rego Park II | Anchor | Kohl's
Operating Properties
Area of property (in square feet)	133
The Alexander apartment tower
Operating Properties
Area of property (in square feet)	255
Number of property units | unit	312
Flushing
Operating Properties
Area of property (in square feet)	167
Number of extensions | extension	1
Length of extension	10 years
Rego Park III
Operating Properties
Area of land	140