Organization and Basis of Presentation - Schedule of Interests in Investment Properties (Details)	Dec. 31, 2023 ft² building
Real estate properties
Number of Buildings | building	50
Approximate Square Feet	29,695,841
Weighted Average Occupancy (as a percent)	89.20%
Manhattan
Real estate properties
Number of Buildings | building	41
Approximate Square Feet	28,470,775
Weighted Average Occupancy (as a percent)	89.50%
Commercial Property
Real estate properties
Number of Buildings | building	48
Approximate Square Feet	29,333,575
Weighted Average Occupancy (as a percent)	89.00%
Office | Alternative strategy portfolio
Real estate properties
Number of Buildings | building	1
Approximate Square Feet	2,048,725
Office | Manhattan
Real estate properties
Number of Buildings | building	25
Approximate Square Feet	23,811,315
Weighted Average Occupancy (as a percent)	89.40%
Office | Suburban
Real estate properties
Number of Buildings | building	7
Approximate Square Feet	862,800
Weighted Average Occupancy (as a percent)	77.10%
Retail | Alternative strategy portfolio
Real estate properties
Number of Buildings | building	8
Approximate Square Feet	286,738
Retail | Manhattan
Real estate properties
Number of Buildings | building	10
Approximate Square Feet	322,332
Weighted Average Occupancy (as a percent)	91.20%
Development/Redevelopment | Alternative strategy portfolio
Real estate properties
Number of Buildings | building	2
Approximate Square Feet	1,496,931
Development/Redevelopment | Manhattan
Real estate properties
Number of Buildings | building	6
Approximate Square Feet	4,337,128
Residential | Manhattan
Real estate properties
Number of Buildings | building	2
Approximate Square Feet	362,266
Weighted Average Occupancy (as a percent)	99.00%
Consolidated
Real estate properties
Number of Buildings | building	27
Approximate Square Feet	10,886,630
Consolidated | Manhattan
Real estate properties
Number of Buildings | building	19
Approximate Square Feet	9,883,448
Consolidated | Commercial Property
Real estate properties
Number of Buildings | building	26
Approximate Square Feet	10,746,248
Consolidated | Office | Manhattan
Real estate properties
Number of Buildings | building	13
Approximate Square Feet	8,399,141
Consolidated | Office | Suburban
Real estate properties
Number of Buildings | building	7
Approximate Square Feet	862,800
Consolidated | Retail | Manhattan
Real estate properties
Number of Buildings | building	3
Approximate Square Feet	40,536
Consolidated | Retail | Manhattan | 7 Dey/185 Broadway
Real estate properties
Approximate Square Feet	140,382
Consolidated | Development/Redevelopment | Manhattan
Real estate properties
Number of Buildings | building	3
Approximate Square Feet	1,443,771
Consolidated | Residential | Manhattan
Real estate properties
Number of Buildings | building	1
Approximate Square Feet	140,382
Consolidated | Residential | Manhattan | 7 Dey/185 Broadway
Real estate properties
Approximate Square Feet	50,206
Unconsolidated
Real estate properties
Number of Buildings | building	23
Approximate Square Feet	18,809,211
Unconsolidated | Manhattan
Real estate properties
Number of Buildings | building	22
Approximate Square Feet	18,587,327
Unconsolidated | Commercial Property
Real estate properties
Number of Buildings | building	22
Approximate Square Feet	18,587,327
Unconsolidated | Office | Manhattan
Real estate properties
Number of Buildings | building	12
Approximate Square Feet	15,412,174
Unconsolidated | Office | Suburban
Real estate properties
Number of Buildings | building	0
Approximate Square Feet	0
Unconsolidated | Retail | Manhattan
Real estate properties
Number of Buildings | building	7
Approximate Square Feet	281,796
Unconsolidated | Development/Redevelopment | Manhattan
Real estate properties
Number of Buildings | building	3
Approximate Square Feet	2,893,357
Unconsolidated | Residential | Manhattan
Real estate properties
Number of Buildings | building	1
Approximate Square Feet	221,884