Organization and Basis of Presentation - Schedule of Commercial Office Properties (Details)	Jun. 30, 2026 ft² building
Manhattan
Real estate properties
Number of Buildings \| building	36
Approximate square feet unaudited (sqft)	25,543,700
Weighted average leased occupancy	94.70%
Commercial properties
Real estate properties
Number of Buildings \| building	42
Approximate square feet unaudited (sqft)	26,276,500
Weighted average leased occupancy	94.20%
Office \| Manhattan
Real estate properties
Number of Buildings \| building	27
Approximate square feet unaudited (sqft)	23,971,485
Weighted average leased occupancy	94.80%
Office \| Suburban
Real estate properties
Number of Buildings \| building	6
Approximate square feet unaudited (sqft)	732,800
Weighted average leased occupancy	79.90%
Retail \| Manhattan
Real estate properties
Number of Buildings \| building	4
Approximate square feet unaudited (sqft)	351,264
Weighted average leased occupancy	86.50%
Development/Redevelopment \| Manhattan
Real estate properties
Number of Buildings \| building	5
Approximate square feet unaudited (sqft)	1,220,951
Residential \| Manhattan
Real estate properties
Number of Buildings \| building	2
Approximate square feet unaudited (sqft)	444,739
Weighted average leased occupancy	99.40%
Core portfolio
Real estate properties
Number of Buildings \| building	44
Approximate square feet unaudited (sqft)	26,721,239
Core portfolio \| Manhattan
Real estate properties
Weighted average leased occupancy	94.30%
Alternative Strategy Portfolio \| Manhattan
Real estate properties
Number of Buildings \| building	4
Approximate square feet unaudited (sqft)	2,492,157
Weighted average leased occupancy	58.70%
Consolidated \| Manhattan
Real estate properties
Number of Buildings \| building	25
Approximate square feet unaudited (sqft)	11,662,348
Consolidated \| Commercial properties
Real estate properties
Number of Buildings \| building	31
Approximate square feet unaudited (sqft)	12,395,148
Consolidated \| Office \| Manhattan
Real estate properties
Number of Buildings \| building	17
Approximate square feet unaudited (sqft)	10,102,852
Consolidated \| Office \| Suburban
Real estate properties
Number of Buildings \| building	6
Approximate square feet unaudited (sqft)	732,800
Consolidated \| Retail \| Manhattan
Real estate properties
Number of Buildings \| building	3
Approximate square feet unaudited (sqft)	338,545
Consolidated \| Retail \| Manhattan \| 315 West 33rd Street
Real estate properties
Approximate square feet unaudited (sqft)	270,132
Consolidated \| Development/Redevelopment \| Manhattan
Real estate properties
Number of Buildings \| building	5
Approximate square feet unaudited (sqft)	1,220,951
Consolidated \| Residential \| Manhattan
Real estate properties
Number of Buildings \| building	1
Approximate square feet unaudited (sqft)	222,855
Consolidated \| Residential \| Manhattan \| 315 West 33rd Street
Real estate properties
Approximate square feet unaudited (sqft)	222,855
Consolidated \| Core portfolio
Real estate properties
Number of Buildings \| building	32
Approximate square feet unaudited (sqft)	12,618,003
Consolidated \| Alternative Strategy Portfolio \| Manhattan
Real estate properties
Number of Buildings \| building	0
Approximate square feet unaudited (sqft)	0
Unconsolidated \| Manhattan
Real estate properties
Number of Buildings \| building	11
Approximate square feet unaudited (sqft)	13,881,352
Unconsolidated \| Commercial properties
Real estate properties
Number of Buildings \| building	11
Approximate square feet unaudited (sqft)	13,881,352
Unconsolidated \| Office \| Manhattan
Real estate properties
Number of Buildings \| building	10
Approximate square feet unaudited (sqft)	13,868,633
Unconsolidated \| Office \| Suburban
Real estate properties
Number of Buildings \| building	0
Approximate square feet unaudited (sqft)	0
Unconsolidated \| Retail \| Manhattan
Real estate properties
Number of Buildings \| building	1
Approximate square feet unaudited (sqft)	12,719
Unconsolidated \| Development/Redevelopment \| Manhattan
Real estate properties
Number of Buildings \| building	0
Approximate square feet unaudited (sqft)	0
Unconsolidated \| Residential \| Manhattan
Real estate properties
Number of Buildings \| building	1
Approximate square feet unaudited (sqft)	221,884
Unconsolidated \| Core portfolio
Real estate properties
Number of Buildings \| building	12
Approximate square feet unaudited (sqft)	14,103,236
Unconsolidated \| Alternative Strategy Portfolio \| Manhattan
Real estate properties
Number of Buildings \| building	4
Approximate square feet unaudited (sqft)	2,492,157

Organization and Basis of Presentation - Schedule of Commercial Office Properties (Details)

Jun. 30, 2026

ft²

building

Manhattan

Real estate properties

Number of Buildings | building

Approximate square feet unaudited (sqft)

25,543,700

Weighted average leased occupancy

94.70%

Commercial properties