Summary Of Significant Accounting Policies (Narrative) (Details) $ in Thousands			3 Months Ended		6 Months Ended
	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of VIEs			9		9
Separate Unrestricted Cash For Deferred Compensation Plan.		$ 36,100	$ 36,500		$ 36,500
Impairment loss			0	$ 0	13,615	$ 0
Unsecured commercial paper		0	500,000		500,000
Gains from investments in securities			315	1,571	2,587	3,236
Prepaid Expense and Other Assets		64,230	$ 86,188		$ 86,188
Unconsolidated Joint Ventures [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of VIEs			0		0
Deferred Compensation, Excluding Share-Based Payments and Retirement Benefits
Summary Of Significant Accounting Policies [Line Items]
Gains from investments in securities			$ 300	$ 1,600	$ 2,600	$ 3,200
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		$ 4,600	5,800		5,800
US Treasury Bill Securities
Summary Of Significant Accounting Policies [Line Items]
U.S. Treasury Bill, Term of Contract		3 months
3-Month United States Treasury Bills		$ 302,700	$ 0		$ 0
Variable Interest Entity, Primary Beneficiary [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of VIEs			9		9
Prepaid Expense and Other Assets		$ 11,824	$ 14,753		$ 14,753
Commercial Real Estate Properties [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of VIEs			5		5