Organization and Basis of Presentation - Schedule of Interests in Investment Properties (Details)	Dec. 31, 2025 ft² building
Manhattan
Real estate properties
Number of Buildings | building	36
Approximate Square Feet	24,912,815
Weighted Average Occupancy (as a percent)	92.90%
Commercial Property
Real estate properties
Number of Buildings | building	42
Approximate Square Feet	25,645,615
Weighted Average Occupancy (as a percent)	92.50%
Office | Manhattan
Real estate properties
Number of Buildings | building	26
Approximate Square Feet	23,349,485
Weighted Average Occupancy (as a percent)	93.00%
Office | Suburban
Real estate properties
Number of Buildings | building	6
Approximate Square Feet	732,800
Weighted Average Occupancy (as a percent)	79.40%
Retail | Manhattan
Real estate properties
Number of Buildings | building	5
Approximate Square Feet	313,347
Weighted Average Occupancy (as a percent)	84.80%
Development/Redevelopment | Manhattan
Real estate properties
Number of Buildings | building	5
Approximate Square Feet	1,249,983
Residential | Manhattan
Real estate properties
Number of Buildings | building	2
Approximate Square Feet	585,121
Weighted Average Occupancy (as a percent)	98.70%
Core Portfolio
Real estate properties
Number of Buildings | building	44
Approximate Square Feet	26,230,736
Core Portfolio | Manhattan
Real estate properties
Weighted Average Occupancy (as a percent)	92.60%
Alternative strategy portfolio | Manhattan
Real estate properties
Number of Buildings | building	5
Approximate Square Feet	2,509,307
Weighted Average Occupancy (as a percent)	59.30%
Consolidated | Manhattan
Real estate properties
Number of Buildings | building	26
Approximate Square Feet	11,044,182
Consolidated | Commercial Property
Real estate properties
Number of Buildings | building	32
Approximate Square Feet	11,776,982
Consolidated | Office | Manhattan
Real estate properties
Number of Buildings | building	16
Approximate Square Feet	9,480,852
Consolidated | Office | Suburban
Real estate properties
Number of Buildings | building	6
Approximate Square Feet	732,800
Consolidated | Retail | Manhattan
Real estate properties
Number of Buildings | building	5
Approximate Square Feet	313,347
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	5
Approximate Square Feet	1,249,983
Consolidated | Residential | Manhattan
Real estate properties
Number of Buildings | building	1
Approximate Square Feet	363,237
Consolidated | Residential | Manhattan | 7 Dey/185 Broadway
Real estate properties
Approximate Square Feet	50,206
Consolidated | Core Portfolio
Real estate properties
Number of Buildings | building	33
Approximate Square Feet	12,140,219
Consolidated | Alternative strategy portfolio | Manhattan
Real estate properties
Number of Buildings | building	0
Approximate Square Feet	0
Unconsolidated | Manhattan
Real estate properties
Number of Buildings | building	10
Approximate Square Feet	13,868,633
Unconsolidated | Commercial Property
Real estate properties
Number of Buildings | building	10
Approximate Square Feet	13,868,633
Unconsolidated | Office | Manhattan
Real estate properties
Number of Buildings | building	10
Approximate Square Feet	13,868,633
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	0
Approximate Square Feet	0
Unconsolidated | Development/Redevelopment | Manhattan
Real estate properties
Number of Buildings | building	0
Approximate Square Feet	0
Unconsolidated | Residential | Manhattan
Real estate properties
Number of Buildings | building	1
Approximate Square Feet	221,884
Unconsolidated | Core Portfolio
Real estate properties
Number of Buildings | building	11
Approximate Square Feet	14,090,517
Unconsolidated | Alternative strategy portfolio | Manhattan
Real estate properties
Number of Buildings | building	5
Approximate Square Feet	2,509,307