Organization and Basis of Presentation - Schedule of Commercial Office Properties (Details) $ in Billions	9 Months Ended
	Sep. 30, 2021 USD ($) ft² building shares
Real estate properties
Number of Buildings | building	61
Approximate Square Feet unaudited (sqft) | ft²	28,035,572
Weighted Average Occupancy unaudited (as a percent)	92.10%
Debt and preferred equity investments including investments held by unconsolidated joint ventures | $	$ 1.1
Debt and preferred equity investments and other financing receivables included in other balance sheet items | $	$ 0.1
Number of shares to be received on redemption of one unit of limited partnership interests (shares) | shares	1
Commercial properties
Real estate properties
Number of Buildings | building	54
Approximate Square Feet unaudited (sqft) | ft²	27,507,388
Weighted Average Occupancy unaudited (as a percent)	92.00%
Managed office properties
Real estate properties
Number of Buildings | building	2
Approximate Square Feet unaudited (sqft) | ft²	2,100,000
Consolidated properties
Real estate properties
Number of Buildings | building	33
Approximate Square Feet unaudited (sqft) | ft²	12,007,951
Consolidated properties | Commercial properties
Real estate properties
Number of Buildings | building	32
Approximate Square Feet unaudited (sqft) | ft²	11,925,701
Unconsolidated properties
Real estate properties
Number of Buildings | building	28
Approximate Square Feet unaudited (sqft) | ft²	16,027,621
Unconsolidated properties | Commercial properties
Real estate properties
Number of Buildings | building	22
Approximate Square Feet unaudited (sqft) | ft²	15,581,687
Manhattan
Real estate properties
Number of Buildings | building	47
Approximate Square Feet unaudited (sqft) | ft²	26,644,588
Weighted Average Occupancy unaudited (as a percent)	92.50%
Manhattan | Office
Real estate properties
Number of Buildings | building	24
Approximate Square Feet unaudited (sqft) | ft²	20,503,228
Weighted Average Occupancy unaudited (as a percent)	92.50%
Manhattan | Retail
Real estate properties
Number of Buildings | building	11
Approximate Square Feet unaudited (sqft) | ft²	319,884
Weighted Average Occupancy unaudited (as a percent)	94.80%
Manhattan | Development/Redevelopment
Real estate properties
Number of Buildings | building	11
Approximate Square Feet unaudited (sqft) | ft²	5,813,792
Manhattan | Fee Interest
Real estate properties
Number of Buildings | building	1
Approximate Square Feet unaudited (sqft) | ft²	7,684
Manhattan | Residential
Real estate properties
Number of Buildings | building	7
Approximate Square Feet unaudited (sqft) | ft²	528,184
Weighted Average Occupancy unaudited (as a percent)	95.60%
Manhattan | Consolidated properties
Real estate properties
Number of Buildings | building	25
Approximate Square Feet unaudited (sqft) | ft²	11,062,901
Manhattan | Consolidated properties | Office
Real estate properties
Number of Buildings | building	14
Approximate Square Feet unaudited (sqft) | ft²	8,499,045
Manhattan | Consolidated properties | Retail
Real estate properties
Number of Buildings | building	2
Approximate Square Feet unaudited (sqft) | ft²	17,888
Manhattan | Consolidated properties | Development/Redevelopment
Real estate properties
Number of Buildings | building	8
Approximate Square Feet unaudited (sqft) | ft²	2,538,284
Manhattan | Consolidated properties | Fee Interest
Real estate properties
Number of Buildings | building	1
Approximate Square Feet unaudited (sqft) | ft²	7,684
Manhattan | Consolidated properties | Residential
Real estate properties
Number of Buildings | building	1
Approximate Square Feet unaudited (sqft) | ft²	82,250
Manhattan | Unconsolidated properties
Real estate properties
Number of Buildings | building	22
Approximate Square Feet unaudited (sqft) | ft²	15,581,687
Manhattan | Unconsolidated properties | Office
Real estate properties
Number of Buildings | building	10
Approximate Square Feet unaudited (sqft) | ft²	12,004,183
Manhattan | Unconsolidated properties | Retail
Real estate properties
Number of Buildings | building	9
Approximate Square Feet unaudited (sqft) | ft²	301,996
Manhattan | Unconsolidated properties | Development/Redevelopment
Real estate properties
Number of Buildings | building	3
Approximate Square Feet unaudited (sqft) | ft²	3,275,508
Manhattan | Unconsolidated properties | Fee Interest
Real estate properties
Number of Buildings | building	0
Approximate Square Feet unaudited (sqft) | ft²	0
Manhattan | Unconsolidated properties | Residential
Real estate properties
Number of Buildings | building	6
Approximate Square Feet unaudited (sqft) | ft²	445,934
Suburban | Office
Real estate properties
Number of Buildings | building	7
Approximate Square Feet unaudited (sqft) | ft²	862,800
Weighted Average Occupancy unaudited (as a percent)	80.50%
Suburban | Consolidated properties | Office
Real estate properties
Number of Buildings | building	7
Approximate Square Feet unaudited (sqft) | ft²	862,800
Suburban | Unconsolidated properties | Office
Real estate properties
Number of Buildings | building	0
Approximate Square Feet unaudited (sqft) | ft²	0