Organization and Basis of Presentation - Schedule of Commercial Office Properties (Details)	Sep. 30, 2023 ft² building
Real estate properties
Number of Buildings | building	51
Approximate Square Feet unaudited (sqft)	29,708,910
Commercial properties
Real estate properties
Number of Buildings | building	49
Approximate Square Feet unaudited (sqft)	29,346,644
Consolidated
Real estate properties
Number of Buildings | building	27
Approximate Square Feet unaudited (sqft)	10,886,630
Consolidated | Commercial properties
Real estate properties
Number of Buildings | building	26
Approximate Square Feet unaudited (sqft)	10,746,248
Unconsolidated
Real estate properties
Number of Buildings | building	24
Approximate Square Feet unaudited (sqft)	18,822,280
Unconsolidated | Commercial properties
Real estate properties
Number of Buildings | building	23
Approximate Square Feet unaudited (sqft)	18,600,396
Manhattan
Real estate properties
Number of Buildings | building	42
Approximate Square Feet unaudited (sqft)	28,483,844
Manhattan | Office
Real estate properties
Number of Buildings | building	25
Approximate Square Feet unaudited (sqft)	23,811,315
Weighted Average Leased Occupancy	89.30%
Manhattan | Retail
Real estate properties
Number of Buildings | building	10
Approximate Square Feet unaudited (sqft)	312,753
Weighted Average Leased Occupancy	91.00%
Manhattan | Development/Redevelopment
Real estate properties
Number of Buildings | building	7
Approximate Square Feet unaudited (sqft)	4,359,776
Manhattan | Residential
Real estate properties
Number of Buildings | building	2
Approximate Square Feet unaudited (sqft)	362,266
Weighted Average Leased Occupancy	99.00%
Manhattan | Consolidated
Real estate properties
Number of Buildings | building	19
Approximate Square Feet unaudited (sqft)	9,883,448
Manhattan | Consolidated | Office
Real estate properties
Number of Buildings | building	13
Approximate Square Feet unaudited (sqft)	8,399,141
Manhattan | Consolidated | Retail
Real estate properties
Number of Buildings | building	2
Approximate Square Feet unaudited (sqft)	17,888
Manhattan | Consolidated | Retail | 7 Dey / 185 Broadway
Real estate properties
Approximate Square Feet unaudited (sqft)	140,382
Manhattan | Consolidated | Development/Redevelopment
Real estate properties
Number of Buildings | building	4
Approximate Square Feet unaudited (sqft)	1,466,419
Manhattan | Consolidated | Residential
Real estate properties
Number of Buildings | building	1
Approximate Square Feet unaudited (sqft)	140,382
Manhattan | Consolidated | Residential | 7 Dey / 185 Broadway
Real estate properties
Approximate Square Feet unaudited (sqft)	50,206
Manhattan | Unconsolidated
Real estate properties
Number of Buildings | building	23
Approximate Square Feet unaudited (sqft)	18,600,396
Manhattan | Unconsolidated | Office
Real estate properties
Number of Buildings | building	12
Approximate Square Feet unaudited (sqft)	15,412,174
Manhattan | Unconsolidated | Retail
Real estate properties
Number of Buildings | building	8
Approximate Square Feet unaudited (sqft)	294,865
Manhattan | Unconsolidated | Development/Redevelopment
Real estate properties
Number of Buildings | building	3
Approximate Square Feet unaudited (sqft)	2,893,357
Manhattan | Unconsolidated | Residential
Real estate properties
Number of Buildings | building	1
Approximate Square Feet unaudited (sqft)	221,884
Suburban | Office
Real estate properties
Number of Buildings | building	7
Approximate Square Feet unaudited (sqft)	862,800
Weighted Average Leased Occupancy	77.40%
Suburban | Consolidated | Office
Real estate properties
Number of Buildings | building	7
Approximate Square Feet unaudited (sqft)	862,800
Suburban | Unconsolidated | Office
Real estate properties
Number of Buildings | building	0
Approximate Square Feet unaudited (sqft)	0