Schedule III: Real Estate and Accumulated depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Encumbrances	$ 1,096,544
Initial cost of Land	19,985
Initial cost of Building and Leasehold improvements	24,435
Costs capitalized subsequent to acquisition	1,040,178
Carrying amount of Land	33,050
Carrying amount of Buildings and Leasehold improvements	1,029,504
Development and Construction in progress	22,044
Total	1,084,598	$ 1,069,426	$ 1,071,043	$ 1,041,342
Accumulated Depreciation and Amortization	396,268	$ 370,557	$ 350,122	$ 324,499
Deferred debt issuance costs, net	5,493
Net basis difference of assets and liabilities between tax basis and GAAP basis	137,734
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	93,119
Carrying amount of Land	1,647
Carrying amount of Buildings and Leasehold improvements	94,697
Development and Construction in progress	7,375
Total	103,719
Accumulated Depreciation and Amortization	$ 43,870
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	392,696
Carrying amount of Land	3,127
Carrying amount of Buildings and Leasehold improvements	391,367
Development and Construction in progress	2,796
Total	397,290
Accumulated Depreciation and Amortization	$ 130,713
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	119,112
Carrying amount of Land	0
Carrying amount of Buildings and Leasehold improvements	119,112
Development and Construction in progress	0
Total	119,112
Accumulated Depreciation and Amortization	$ 27,856
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 | Rego Park III
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation
Encumbrances	$ 0
Initial cost of Land	779
Initial cost of Building and Leasehold improvements	0
Costs capitalized subsequent to acquisition	12,399
Carrying amount of Land	779
Carrying amount of Buildings and Leasehold improvements	526
Development and Construction in progress	11,873
Total	13,178
Accumulated Depreciation and Amortization	$ 396
Date acquired	1992
New York | Rego Park III | 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	5 years
New York | Rego Park III | 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	15 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	$ 1,264
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	422,959
Carrying amount of Land	27,497
Carrying amount of Buildings and Leasehold improvements	422,249
Development and Construction in progress	0
Total	449,746
Accumulated Depreciation and Amortization	$ 192,169
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