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Summary Of Significant Accounting Policies (Narrative) (Details)
 12 Months Ended
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.