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Unsecured Senior Notes (Narrative) (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 16, 2021
Feb. 14, 2021
Mar. 31, 2021
Mar. 31, 2020
Debt Instrument [Line Items]        
Repayments of Unsecured Debt     $ 843,710 $ 0
Loss from early extinguishment of debt     898 0
Proceeds from unsecured senior notes     846,345 0
Boston Properties Limited Partnership        
Debt Instrument [Line Items]        
Repayments of Unsecured Debt     843,710 0
Loss from early extinguishment of debt     898 0
Proceeds from unsecured senior notes     $ 846,345 $ 0
Debt Instrument, Covenant Description     The indenture relating to the unsecured senior notes contains certain financial restrictions and requirements, including (1) a leverage ratio not to exceed 60%, (2) a secured debt leverage ratio not to exceed 50%, (3) an interest coverage ratio of greater than 1.50, and (4) an unencumbered asset value of not less than 150% of unsecured debt.  
Debt Instrument, Covenant Compliance     At March 31, 2021, Boston Properties Limited Partnership was in compliance with each of these financial restrictions and requirements.  
Senior Notes | Boston Properties Limited Partnership        
Debt Instrument [Line Items]        
Debt     $ 9,700,000  
2.671% unsecured senior notes | Senior Notes | Boston Properties Limited Partnership        
Debt Instrument [Line Items]        
Debt $ 850,000   $ 850,000  
Debt Instrument, Interest Rate, Stated Percentage 2.55%   2.55%  
Senior Notes Pricing 99.57%      
Debt Instrument, Interest Rate, Effective Percentage 2.671%   2.671% [1]  
Proceeds from unsecured senior notes $ 839,200      
4.289% unsecured senior notes | Senior Notes | Boston Properties Limited Partnership        
Debt Instrument [Line Items]        
Debt   $ 850,000    
Debt Instrument, Interest Rate, Stated Percentage   4.125%    
Repayments of Unsecured Debt   $ 858,700    
Debt Instrument, Increase, Accrued Interest   8,700    
Loss from early extinguishment of debt   $ 400    
[1] Yield on issuance date including the effects of discounts on the notes, settlements of interest rate contracts and the amortization of financing costs.