Corporate Indebtedness - Junior Subordinated Deferrable Interest Debentures and Principal Maturities (Details) - USD ($)	1 Months Ended	12 Months Ended
Jun. 30, 2005	Dec. 31, 2019
Principal Repayments and Joint Venture Debt
2020		$ 468,824,000
2021		601,546,000
2022		1,338,805,000
2023		1,597,301,000
2024		478,781,000
Thereafter		1,066,626,000
Scheduled Amortization and Principal Repayments
Total fixed rate and floating rate debt		$ 5,551,883,000
Trust Preferred Securities
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 100,000,000.0
Trust Preferred Securities \| LIBOR
Debt Instrument [Line Items]
Interest rate added to base rate (as a percent)		1.25%
Joint venture
Principal Repayments and Joint Venture Debt
2020		$ 811,628,000
2021		805,276,000
2022		268,952,000
2023		311,436,000
2024		17,022,000
Thereafter		1,813,821,000
Repayments of principal		4,028,135,000
Joint venture \| Mortgages and other loans payable
Scheduled Amortization
2020		11,118,000
2021		11,638,000
2022		9,430,000
2023		7,301,000
2024		6,032,000
Thereafter		3,258,000
Principal Repayments and Joint Venture Debt
2020		207,706,000
2021		239,908,000
2022		529,375,000
2023		50,000,000
2024		272,749,000
Thereafter		863,368,000
Future Amortization of Debt		48,777,000
Repayments of principal		2,163,106,000
Joint venture \| Trust Preferred Securities
Principal Repayments and Joint Venture Debt
2020		0
2021		0
2022		0
2023		0
2024		0
Thereafter		100,000,000
Scheduled Amortization and Principal Repayments
Total fixed rate and floating rate debt		100,000,000
Joint venture \| Revolving Credit Facility
Principal Repayments and Joint Venture Debt
2020		0
2021		0
2022		0
2023		240,000,000
2024		0
Thereafter		0
Scheduled Amortization and Principal Repayments
Total fixed rate and floating rate debt		240,000,000
Joint venture \| Unsecured Term Loans
Principal Repayments and Joint Venture Debt
2020		0
2021		0
2022		0
2023		1,300,000,000
2024		200,000,000
Thereafter		0
Scheduled Amortization and Principal Repayments
Total fixed rate and floating rate debt		1,500,000,000
Joint venture \| Senior Unsecured Notes
Principal Repayments and Joint Venture Debt
2020		250,000,000
2021		350,000,000
2022		800,000,000
2023		0
2024		0
Thereafter		100,000,000
Scheduled Amortization and Principal Repayments
Total fixed rate and floating rate debt		$ 1,500,000,000

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