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Summary Of Significant Accounting Policies (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 29, 2025 USD ($)	Dec. 31, 2024 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Separate Unrestricted Cash For Deferred Compensation Plan.	$ 43,400		$ 43,400			$ 39,400
Gains from investments in securities	2,400	$ 2,198	4,635	$ 4,785
Prepaid Expense and Other Assets	137,561		137,561			70,839
Unsecured commercial paper	$ 750,000		$ 750,000			500,000
Number of VIEs	11		11
Impairment loss	$ 68,901	0	$ 68,901	13,615
Commercial Paper
Summary Of Significant Accounting Policies [Line Items]
Unsecured commercial paper	$ 750,000		$ 750,000
Unconsolidated Joint Ventures [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of VIEs	3		3
Boston Properties Limited Partnership
Summary Of Significant Accounting Policies [Line Items]
Gains from investments in securities	$ 2,400	2,198	$ 4,635	4,785
Prepaid Expense and Other Assets	137,561		137,561			70,839
Unsecured commercial paper	750,000		750,000			500,000
Impairment loss	65,988	0	65,988	13,615
Deferred Compensation, Excluding Share-Based Payments and Retirement Benefits
Summary Of Significant Accounting Policies [Line Items]
Gains from investments in securities	2,400	$ 2,200	4,600	$ 4,800
Environmental Focused Investment Fund
Summary Of Significant Accounting Policies [Line Items]
Prepaid Expense and Other Assets	9,400		9,400			7,100
Variable Interest Entity, Primary Beneficiary [Member]
Summary Of Significant Accounting Policies [Line Items]
Prepaid Expense and Other Assets	$ 51,682		$ 51,682			15,036
Number of VIEs	8		8
Variable Interest Entity, Primary Beneficiary [Member] | Boston Properties Limited Partnership
Summary Of Significant Accounting Policies [Line Items]
Prepaid Expense and Other Assets	$ 51,682		$ 51,682			$ 15,036
Convertible Debt | 2.00% unsecured exchangeable senior notes
Summary Of Significant Accounting Policies [Line Items]
Debt					$ 1,000,000
Debt Instrument, Interest Rate, Stated Percentage					2.00%
Convertible Debt | Boston Properties Limited Partnership | 2.00% unsecured exchangeable senior notes
Summary Of Significant Accounting Policies [Line Items]
Debt					$ 1,000,000
Debt Instrument, Interest Rate, Stated Percentage					2.00%
Commercial Real Estate Properties [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of VIEs	6		6
Wholly Owned Properties
Summary Of Significant Accounting Policies [Line Items]
Impairment loss	$ 68,900
Wholly Owned Properties | Boston Properties Limited Partnership
Summary Of Significant Accounting Policies [Line Items]
Impairment loss	$ 66,000

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Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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