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Summary Of Significant Accounting Policies (Narrative) (Details) $ in Thousands				3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of VIEs	9			9		9
Separate Unrestricted Cash For Deferred Compensation Plan.	$ 38,900		$ 36,100	$ 38,900		$ 38,900
Impairment loss				0	$ 0	13,615	$ 0
Unsecured commercial paper	500,000		0	500,000		500,000
Gains (losses) from investments in securities				2,198	(925)	4,785	2,311
Prepaid Expense and Other Assets	$ 132,078		64,230	$ 132,078		$ 132,078
Unconsolidated Joint Ventures [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of VIEs	0			0		0
Deferred Compensation, Excluding Share-Based Payments and Retirement Benefits
Summary Of Significant Accounting Policies [Line Items]
Gains (losses) from investments in securities				$ 2,200	$ (900)	$ 4,800	$ 2,300
Shady Grove Innovation District [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairment loss		$ 13,600				13,600
Environmental Focused Investment Fund
Summary Of Significant Accounting Policies [Line Items]
Prepaid Expense and Other Assets	$ 6,700		$ 4,600	6,700		6,700
US Treasury Bill Securities
Summary Of Significant Accounting Policies [Line Items]
U.S. Treasury Bill, Term of Contract	3 months		3 months
3-Month United States Treasury Bills	$ 175,900		$ 302,700	$ 175,900		$ 175,900
Variable Interest Entity, Primary Beneficiary [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of VIEs	9			9		9
Prepaid Expense and Other Assets	$ 50,275		$ 11,824	$ 50,275		$ 50,275
Commercial Real Estate Properties [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of VIEs	5			5		5

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