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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 |

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