Organization and Basis of Presentation - Schedule of Commercial Office Properties (Details) $ in Billions	6 Months Ended
	Jun. 30, 2021 USD ($) ft² building shares
Real estate properties
Number of Buildings | building	60
Approximate Square Feet unaudited (sqft) | ft²	27,962,796
Weighted Average Occupancy unaudited (as a percent)	92.00%
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	52
Approximate Square Feet unaudited (sqft) | ft²	27,144,130
Weighted Average Occupancy unaudited (as a percent)	92.60%
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	32
Approximate Square Feet unaudited (sqft) | ft²	13,127,419
Consolidated properties | Commercial properties
Real estate properties
Number of Buildings | building	31
Approximate Square Feet unaudited (sqft) | ft²	13,045,169
Unconsolidated properties
Real estate properties
Number of Buildings | building	28
Approximate Square Feet unaudited (sqft) | ft²	14,835,377
Unconsolidated properties | Commercial properties
Real estate properties
Number of Buildings | building	21
Approximate Square Feet unaudited (sqft) | ft²	14,098,961
Manhattan
Real estate properties
Number of Buildings | building	45
Approximate Square Feet unaudited (sqft) | ft²	26,281,330
Weighted Average Occupancy unaudited (as a percent)	93.00%
Manhattan | Office
Real estate properties
Number of Buildings | building	25
Approximate Square Feet unaudited (sqft) | ft²	21,128,528
Weighted Average Occupancy unaudited (as a percent)	93.00%
Manhattan | Retail
Real estate properties
Number of Buildings | building	10
Approximate Square Feet unaudited (sqft) | ft²	312,036
Weighted Average Occupancy unaudited (as a percent)	90.50%
Manhattan | Development/Redevelopment
Real estate properties
Number of Buildings | building	10
Approximate Square Feet unaudited (sqft) | ft²	4,840,766
Manhattan | Residential
Real estate properties
Number of Buildings | building	8
Approximate Square Feet unaudited (sqft) | ft²	818,666
Weighted Average Occupancy unaudited (as a percent)	74.00%
Manhattan | Consolidated properties
Real estate properties
Number of Buildings | building	24
Approximate Square Feet unaudited (sqft) | ft²	12,182,369
Manhattan | Consolidated properties | Office
Real estate properties
Number of Buildings | building	16
Approximate Square Feet unaudited (sqft) | ft²	10,259,345
Manhattan | Consolidated properties | Retail
Real estate properties
Number of Buildings | building	1
Approximate Square Feet unaudited (sqft) | ft²	10,040
Manhattan | Consolidated properties | Development/Redevelopment
Real estate properties
Number of Buildings | building	7
Approximate Square Feet unaudited (sqft) | ft²	1,912,984
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	21
Approximate Square Feet unaudited (sqft) | ft²	14,098,961
Manhattan | Unconsolidated properties | Office
Real estate properties
Number of Buildings | building	9
Approximate Square Feet unaudited (sqft) | ft²	10,869,183
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	2,927,782
Manhattan | Unconsolidated properties | Residential
Real estate properties
Number of Buildings | building	7
Approximate Square Feet unaudited (sqft) | ft²	736,416
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)	82.40%
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