Schedule III: Real Estate and Accumulated Depreciation - Schedule (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Encumbrances	$ 1,096,544
Initial cost of Land	19,206
Initial cost of Building and Leasehold improvements	24,435
Costs capitalized subsequent to acquisition	1,022,979
Carrying amount of Land	32,271
Carrying amount of Buildings and Leasehold improvements	1,034,068
Development and Construction in progress	281
Total	1,066,620	$ 1,084,598	$ 1,069,426	$ 1,071,043
Accumulated Depreciation and Amortization	415,903	$ 396,268	$ 370,557	$ 350,122
Deferred debt issuance costs, net	3,993
Net basis difference of assets and liabilities between tax basis and GAAP basis	145,246
New York | Rego Park I
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Encumbrances	0
Initial cost of Land	1,647
Initial cost of Building and Leasehold improvements	8,953
Costs capitalized subsequent to acquisition	93,138
Carrying amount of Land	1,647
Carrying amount of Buildings and Leasehold improvements	102,091
Development and Construction in progress	0
Total	103,738
Accumulated Depreciation and Amortization	$ 47,931
Date of Construction	1959
Date acquired	1992
New York | Rego Park I | Minimum
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Life on which Depreciation in Latest Income Statement is Computed	3 years
New York | Rego Park I | Maximum
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Life on which Depreciation in Latest Income Statement is Computed	39 years
New York | Rego Park II | Retail space
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Encumbrances	$ 202,544
Initial cost of Land	3,127
Initial cost of Building and Leasehold improvements	1,467
Costs capitalized subsequent to acquisition	390,267
Carrying amount of Land	3,127
Carrying amount of Buildings and Leasehold improvements	391,453
Development and Construction in progress	281
Total	394,861
Accumulated Depreciation and Amortization	$ 135,791
Date of Construction	2009
Date acquired	1992
New York | Rego Park II | Retail space | Minimum
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Life on which Depreciation in Latest Income Statement is Computed	3 years
New York | Rego Park II | Retail space | Maximum
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Life on which Depreciation in Latest Income Statement is Computed	40 years
New York | The Alexander apartment tower
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Encumbrances	$ 94,000
Initial cost of Land	0
Initial cost of Building and Leasehold improvements	0
Costs capitalized subsequent to acquisition	115,074
Carrying amount of Land	0
Carrying amount of Buildings and Leasehold improvements	115,074
Development and Construction in progress	0
Total	115,074
Accumulated Depreciation and Amortization	$ 27,036
Date of Construction	2016
Date acquired	1992
New York | The Alexander apartment tower | Minimum
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Life on which Depreciation in Latest Income Statement is Computed	3 years
New York | The Alexander apartment tower | Maximum
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Life on which Depreciation in Latest Income Statement is Computed	39 years
New York | Flushing
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Encumbrances	$ 0
Initial cost of Land	0
Initial cost of Building and Leasehold improvements	1,660
Costs capitalized subsequent to acquisition	(107)
Carrying amount of Land	0
Carrying amount of Buildings and Leasehold improvements	1,553
Development and Construction in progress	0
Total	1,553
Accumulated Depreciation and Amortization	$ 1,324
Date of Construction	1975
Date acquired	1992
New York | Lexington Avenue
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Encumbrances	$ 800,000
Initial cost of Land	14,432
Initial cost of Building and Leasehold improvements	12,355
Costs capitalized subsequent to acquisition	424,607
Carrying amount of Land	27,497
Carrying amount of Buildings and Leasehold improvements	423,897
Development and Construction in progress	0
Total	451,394
Accumulated Depreciation and Amortization	$ 203,821
Date of Construction	2003
Date acquired	1992
New York | Lexington Avenue | Minimum
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Life on which Depreciation in Latest Income Statement is Computed	9 years
New York | Lexington Avenue | Maximum
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Life on which Depreciation in Latest Income Statement is Computed	39 years