Corporate Indebtedness - Junior Subordinated Deferrable Interest Debentures and Principal Maturities (Details) - USD ($)	1 Months Ended	12 Months Ended
Jun. 30, 2005	Dec. 31, 2020
Principal Repayments and Joint Venture Debt
2021		$ 660,727,000
2022		1,064,202,000
2023		1,976,599,000
2024		478,034,000
2025		100,829,000
Thereafter		680,969,000
Repayments of principal		$ 4,961,360,000
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)		125.00%
Joint venture
Principal Repayments and Joint Venture Debt
2021		$ 1,085,279,000
2022		540,947,000
2023		491,066,000
2024		617,010,000
2025		1,385,256,000
Thereafter		552,813,000
Repayments of principal		4,672,371,000
Joint venture \| Mortgages and other loans payable
Scheduled Amortization
2021		10,700,000
2022		8,767,000
2023		6,599,000
2024		5,285,000
2025		829,000
Thereafter		930,000
Future Amortization of Debt		33,110,000
Principal Repayments and Joint Venture Debt
2021		300,027,000
2022		255,435,000
2023		560,000,000
2024		272,749,000
2025		0
Thereafter		580,039,000
Repayments of principal		1,968,250,000
Joint venture \| Trust Preferred Securities
Principal Repayments and Joint Venture Debt
2021		0
2022		0
2023		0
2024		0
2025		0
Thereafter		100,000,000
Repayments of principal		100,000,000
Joint venture \| Revolving Credit Facility
Principal Repayments and Joint Venture Debt
2021		0
2022		0
2023		110,000,000
2024		0
2025		0
Thereafter		0
Repayments of principal		110,000,000
Joint venture \| Unsecured Term Loans
Principal Repayments and Joint Venture Debt
2021		0
2022		0
2023		1,300,000,000
2024		200,000,000
2025		0
Thereafter		0
Repayments of principal		1,500,000,000
Joint venture \| Senior Unsecured Notes
Principal Repayments and Joint Venture Debt
2021		350,000,000
2022		800,000,000
2023		0
2024		0
2025		100,000,000
Thereafter		0
Repayments of principal		$ 1,250,000,000

The total expected future amortization of debt.

No definition available.

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The amount of amortization of debt expected to be recognized after the fifth full fiscal year following the date of the most recent balance sheet.

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The amount of amortization of debt expected to be recognized during the fifth full fiscal year following the date of the most recent balance sheet.

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The amount of amortization of debt expected to be recognized during the first full fiscal year following the date of the most recent balance sheet.

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The amount of amortization of debt expected to be recognized during the fourth full fiscal year following the date of the most recent balance sheet.

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The amount of amortization of debt expected to be recognized during the second full fiscal year following the date of the most recent balance sheet.

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The amount of amortization of debt expected to be recognized during the third full fiscal year following the date of the most recent balance sheet.

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Total amount of long-term debt maturing in future periods.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-SubTopic 10
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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
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