Organization and Basis of Presentation - Schedule of Commercial Office Properties (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) ft² building shares	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Real estate properties
Number of Buildings \| building	59
Approximate Square Feet \| ft²	27,716,872
Weighted Average Occupancy unaudited (as a percent)	91.60%
Debt and preferred equity investments including investments held by unconsolidated joint ventures \| $	$ 1,088,723	$ 1,076,542	$ 1,580,306
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 \| ft²	27,188,688
Weighted Average Occupancy unaudited (as a percent)	91.50%
Managed office properties
Real estate properties
Number of Buildings \| building	2
Approximate Square Feet \| ft²	2,100,000
Debt and preferred equity investments including investments held by unconsolidated joint ventures \| $	$ 1,100,000
Debt and preferred equity investments and other financing receivables included in other balance sheet items \| $	$ 10,100
Consolidated properties
Real estate properties
Number of Buildings \| building	31
Approximate Square Feet \| ft²	11,689,251
Consolidated properties \| Commercial properties
Real estate properties
Number of Buildings \| building	30
Approximate Square Feet \| ft²	11,607,001
Unconsolidated properties
Real estate properties
Number of Buildings \| building	28
Approximate Square Feet \| ft²	16,027,621
Unconsolidated properties \| Commercial properties
Real estate properties
Number of Buildings \| building	22
Approximate Square Feet \| ft²	15,581,687
Manhattan
Real estate properties
Number of Buildings \| building	45
Approximate Square Feet \| ft²	26,325,888
Weighted Average Occupancy unaudited (as a percent)	92.00%
Manhattan \| Office
Real estate properties
Number of Buildings \| building	22
Approximate Square Feet \| ft²	20,184,528
Weighted Average Occupancy unaudited (as a percent)	92.10%
Manhattan \| Retail
Real estate properties
Number of Buildings \| building	11
Approximate Square Feet \| ft²	319,884
Weighted Average Occupancy unaudited (as a percent)	91.20%
Manhattan \| Development/Redevelopment
Real estate properties
Number of Buildings \| building	11
Approximate Square Feet \| ft²	5,813,792
Manhattan \| Fee Interest
Real estate properties
Number of Buildings \| building	1
Approximate Square Feet \| ft²	7,684
Manhattan \| Residential
Real estate properties
Number of Buildings \| building	7
Approximate Square Feet \| ft²	528,184
Weighted Average Occupancy unaudited (as a percent)	97.00%
Manhattan \| Consolidated properties
Real estate properties
Number of Buildings \| building	23
Approximate Square Feet \| ft²	10,744,201
Manhattan \| Consolidated properties \| Office
Real estate properties
Number of Buildings \| building	12
Approximate Square Feet \| ft²	8,180,345
Manhattan \| Consolidated properties \| Retail
Real estate properties
Number of Buildings \| building	2
Approximate Square Feet \| ft²	17,888
Manhattan \| Consolidated properties \| Development/Redevelopment
Real estate properties
Number of Buildings \| building	8
Approximate Square Feet \| ft²	2,538,284
Manhattan \| Consolidated properties \| Fee Interest
Real estate properties
Number of Buildings \| building	1
Approximate Square Feet \| ft²	7,684
Manhattan \| Consolidated properties \| Residential
Real estate properties
Number of Buildings \| building	1
Approximate Square Feet \| ft²	82,250
Manhattan \| Unconsolidated properties
Real estate properties
Number of Buildings \| building	22
Approximate Square Feet \| ft²	15,581,687
Manhattan \| Unconsolidated properties \| Office
Real estate properties
Number of Buildings \| building	10
Approximate Square Feet \| ft²	12,004,183
Manhattan \| Unconsolidated properties \| Retail
Real estate properties
Number of Buildings \| building	9
Approximate Square Feet \| ft²	301,996
Manhattan \| Unconsolidated properties \| Development/Redevelopment
Real estate properties
Number of Buildings \| building	3
Approximate Square Feet \| ft²	3,275,508
Manhattan \| Unconsolidated properties \| Fee Interest
Real estate properties
Number of Buildings \| building	0
Approximate Square Feet \| ft²	0
Manhattan \| Unconsolidated properties \| Residential
Real estate properties
Number of Buildings \| building	6
Approximate Square Feet \| ft²	445,934
Suburban \| Office
Real estate properties
Number of Buildings \| building	7
Approximate Square Feet \| ft²	862,800
Weighted Average Occupancy unaudited (as a percent)	78.90%
Suburban \| Consolidated properties \| Office
Real estate properties
Number of Buildings \| building	7
Approximate Square Feet \| ft²	862,800
Suburban \| Unconsolidated properties \| Office
Real estate properties
Number of Buildings \| building	0
Approximate Square Feet \| ft²	0