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Summary Of Significant Accounting Policies (Narrative) (Details) | 12 Months Ended |
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Dec. 31, 2025 USD ($) Year | Dec. 31, 2024 USD ($) | Dec. 31, 2023 USD ($) | Sep. 29, 2025 USD ($)
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Interest capitalized |  | $ 50,626,000 |  | $ 41,976,000 | $ 42,633,000 |
Salaries And Related Costs Capitalized |  | 17,000,000.0 |  | 17,200,000 | 16,100,000 |
Cash FDIC Insured Limit |  | 250,000 |  |  |  |
Separate Unrestricted Cash For Deferred Compensation Plan. |  | 44,400,000 |  | 39,400,000 |  |
Gains from investments in securities |  | 5,481,000 |  | 4,416,000 | 5,556,000 |
Prepaid Expense and Other Assets |  | $ 108,105,000 |  | 70,839,000 |  |
Accounts Receivable, Collection Period Expected | Year |  | 1 |  |  |  |
Above and below market rent adjustments, net |  | $ 7,700,000 |  | 5,500,000 | 19,200,000 |
Unsecured commercial paper |  | $ 750,000,000 |  | 500,000,000 |  |
REIT Distribution Requirement |  | 90.00% |  |  |  |
Company's Taxable Income Distribution |  | 100.00% |  |  |  |
Number of VIEs |  | 11 |  |  |  |
Impairment loss |  | $ 85,803,000 |  | 13,615,000 | 0 |
Gains on sales of real estate |  | 176,732,000 |  | 602,000 | 517,000 |
Straight Line Rent Adjustments |  | 107,100,000 |  | 105,600,000 | $ 99,100,000 |
Interest Rate Cap |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Derivative, Number of Instruments Held |  |  |  |  | 2 |
Derivative, Notional Amount |  |  |  |  | $ 600,000,000.0 |
Losses from interest rate contracts |  | 0 |  | 0 | 79,000 |
Commercial Paper |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Unsecured commercial paper |  | $ 750,000,000.0 |  |  |  |
Unconsolidated Joint Ventures [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Number of VIEs |  | 3 |  |  |  |
Impairment loss |  | $ 745,224,000 | [1] | 0 | 0 |
Equity Method Investment, Other-than-Temporary Impairment | [2] | 145,133,000 |  | 341,338,000 | 272,603,000 |
Gains on sales of real estate |  | 72,818,000 | [3] | 0 | 0 |
Straight Line Rent Adjustments |  | 12,100,000 |  | 13,700,000 | 28,700,000 |
Boston Properties Limited Partnership |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Interest capitalized |  | 50,626,000 |  | 41,976,000 | 42,633,000 |
Gains from investments in securities |  | 5,481,000 |  | 4,416,000 | 5,556,000 |
Prepaid Expense and Other Assets |  | 108,105,000 |  | 70,839,000 |  |
Unsecured commercial paper |  | 750,000,000 |  | 500,000,000 |  |
Debt |  | 9,850,000,000 |  |  |  |
Impairment loss |  | 82,890,000 |  | 13,615,000 | 0 |
Gains on sales of real estate |  | 179,322,000 |  | 602,000 | 517,000 |
Shady Grove Innovation District [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Impairment loss |  |  |  | 13,600,000 |  |
Shady Grove Innovation District [Member] | Boston Properties Limited Partnership |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Impairment loss |  |  |  | 13,600,000 |  |
Environmental Focused Investment Fund |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Prepaid Expense and Other Assets |  | 10,900,000 |  | 7,100,000 |  |
Unrealized gain (loss) on non-real estate investments |  | (300,000) |  | 500,000 | $ 200,000 |
Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Prepaid Expense and Other Assets |  | $ 14,509,000 |  | 15,036,000 |  |
Number of VIEs |  | 8 |  |  |  |
Variable Interest Entity, Primary Beneficiary [Member] | Boston Properties Limited Partnership |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Prepaid Expense and Other Assets |  | $ 14,509,000 |  | $ 15,036,000 |  |
Convertible Debt | 2.00% unsecured exchangeable senior notes |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Debt |  |  |  |  |  | $ 1,000,000,000.0
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 |  |  |  |  |  | $ 1,000,000,000.0
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  |  | 2.00%
Unconsolidated Properties | Gateway Commons Complex [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Number of real estate properties |  | 1 |  |  |  |
Unconsolidated Properties | Gateway Commons Complex [Member] | Unconsolidated Joint Ventures [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Equity Method Investment, Other-than-Temporary Impairment |  | $ 145,100,000 |  |  |  |
Unconsolidated Properties | Colorado Center, Gateway Commons and Safeco Plaza |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Number of real estate properties |  |  |  | 3 |  |
Unconsolidated Properties | Colorado Center, Gateway Commons and Safeco Plaza | Unconsolidated Joint Ventures [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Equity Method Investment, Other-than-Temporary Impairment |  |  |  | $ 341,300,000 |  |
Unconsolidated Properties | Platform 16, 360 Park Avenue South, 200 Fifth Avenue and Safeco Plaza |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Number of real estate properties |  |  |  |  | 4 |
Unconsolidated Properties | Platform 16, 360 Park Avenue South, 200 Fifth Avenue and Safeco Plaza | Unconsolidated Joint Ventures [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Equity Method Investment, Other-than-Temporary Impairment |  |  |  |  | $ 272,600,000 |
Commercial Real Estate Properties [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Number of VIEs |  | 6 |  |  |  |
Wholly Owned Properties |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Impairment loss |  | $ 85,800,000 |  | 13,600,000 |  |
Gains on sales of real estate |  | 176,700,000 |  | 600,000 | 500,000 |
Wholly Owned Properties | Boston Properties Limited Partnership |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Impairment loss |  | 82,900,000 |  | 13,600,000 |  |
Gains on sales of real estate |  | $ 179,300,000 |  | $ 600,000 | $ 500,000 |
[1] | (3)During the year ended December 31, 2025, the joint ventures that own Safeco Plaza and Gateway Commons recognized property level impairment losses in accordance with ASC 360 (See Note 2). In prior periods, the Company had impaired its equity method investment to the estimated fair value for these joint ventures and therefore this is recognized as a basis difference and does not impact Loss from Unconsolidated Joint Ventures on the Consolidated Statements of Operations.
[2] | During the year ended December 31, 2025, the Company recognized an other-than-temporary impairment loss on its investment in Gateway Commons of approximately $145.1 million. During the year ended December 31, 2024, the Company recognized an other-than-temporary impairment loss on its investments in Colorado Center, Gateway Commons and Safeco Plaza of approximately $168.4 million, $126.1 million, and $46.8 million, respectively. During the year ended December 31, 2023, the Company recognized an other-than-temporary impairment loss on its investments in Platform 16, 360 Park Avenue South, 200 Fifth Avenue and Safeco Plaza of approximately $155.2 million, $54.0 million, $33.4 million and $29.9 million, respectively.
[3] | During the year ended December 31, 2025, gains on sales of real estate included Beach Cities Media Campus and 751 Gateway.

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