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Commitments And Contingencies (Details) (USD $)
 1 Months Ended 2 Months Ended 3 Months Ended 12 Months Ended
Mar. 31, 2015
Feb. 28, 2015
Mar. 31, 2015
Dec. 31, 2009
Mar. 11, 2015
Dec. 31, 2014
Jan. 10, 2014
Commitments And Contingencies [Line Items]              
Letter of credit and performance obligations $ 21,600,000bxp_LetterOfCreditAndPerformanceObligation   $ 21,600,000bxp_LetterOfCreditAndPerformanceObligation        
Property insurance program per occurrence limits 1,000,000,000bxp_InsurancePolicyLimit   1,000,000,000bxp_InsurancePolicyLimit        
Per occurrence limit for NBCR Coverage     1,000,000,000bxp_PerOccurrenceLimitForNbcrCoverage        
Value of program trigger 100,000,000bxp_ProgramTriggerValue   100,000,000bxp_ProgramTriggerValue        
Coinsurance of program trigger     15.00%bxp_ProgramTriggerCoinsurance        
Deductible in insurance as a percentage of the value of the affected property, San Francisco     5.00%bxp_EarthquakeDeductibleInsurancePercentageOfValueOfAffectedPropertySanFrancisco        
Per occurrence limit of the earthquake insurance which covers San Francisco region 170,000,000bxp_PerOccurrenceLimitOfEarthQuakeInsuranceSanFrancisco 120,000,000bxp_PerOccurrenceLimitOfEarthQuakeInsuranceSanFrancisco          
Annual aggregate limit of the earthquake insurance which covers San Francisco region 170,000,000bxp_AnnualAggregateLimitOfEarthQuakeInsuranceSanFrancisco 120,000,000bxp_AnnualAggregateLimitOfEarthQuakeInsuranceSanFrancisco          
Amount of earthquake insurance provided by IXP, LLC as direct insurer San Francisco     20,000,000bxp_AmountOfEarthquakeInsuranceProvidedByIxpLlcAsDirectInsurerSanFrancisco        
Earthquake Coverage Included In Builders Risk Policy For Salesforce Tower     60,000,000bxp_EarthquakeCoverageIncludedInBuildersRiskPolicyForImprovementsforSalesforceTower        
Operating partnership guarantee to cover liabilities of IXP 20,000,000bxp_OperatingPartnershipGuaranteeToCoverLiabilitiesOfSubsidiary   20,000,000bxp_OperatingPartnershipGuaranteeToCoverLiabilitiesOfSubsidiary        
767 Venture, LLC [Member]              
Commitments And Contingencies [Line Items]              
Maximum funding obligation 16,400,000us-gaap_GuaranteeObligationsMaximumExposure
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= bxp_SevenSixSevenVentureLlcMember		   16,400,000us-gaap_GuaranteeObligationsMaximumExposure
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= bxp_SevenSixSevenVentureLlcMember		        
Property insurance program per occurrence limits 1,625,000,000bxp_InsurancePolicyLimit
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= bxp_SevenSixSevenVentureLlcMember		   1,625,000,000bxp_InsurancePolicyLimit
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= bxp_SevenSixSevenVentureLlcMember		        
Lehman [Member]              
Commitments And Contingencies [Line Items]              
Bankruptcy claim, amount filed by general creditor       45,300,000bxp_Bankruptcyclaimamountfiledbygeneralcreditor
/ us-gaap_GainContingenciesByNatureAxis
= bxp_LehmanMember		      
Bankruptcy claim amount allowed by court to creditor             45,200,000bxp_Bankruptcyclaimamountallowedbycourttocreditor
/ us-gaap_GainContingenciesByNatureAxis
= bxp_LehmanMember
Bankruptcy Claims, Amount of Claims Settled         4,500,000us-gaap_BankruptcyClaimsAmountOfClaimsSettled
/ us-gaap_GainContingenciesByNatureAxis
= bxp_LehmanMember		 7,700,000us-gaap_BankruptcyClaimsAmountOfClaimsSettled
/ us-gaap_GainContingenciesByNatureAxis
= bxp_LehmanMember		  
Bankruptcy remaining claim amount allowed by court to creditor 33,000,000bxp_Bankruptcyremainingclaimamountallowedbycourttocreditor
/ us-gaap_GainContingenciesByNatureAxis
= bxp_LehmanMember		   33,000,000bxp_Bankruptcyremainingclaimamountallowedbycourttocreditor
/ us-gaap_GainContingenciesByNatureAxis
= bxp_LehmanMember		        
Bankruptcy remaining claim amount based on a privately quoted value 5,500,000bxp_Bankruptcyremainingclaimamountbasedonaprivatelyquotedvalue
/ us-gaap_GainContingenciesByNatureAxis
= bxp_LehmanMember		   5,500,000bxp_Bankruptcyremainingclaimamountbasedonaprivatelyquotedvalue
/ us-gaap_GainContingenciesByNatureAxis
= bxp_LehmanMember		        
John Hancock Tower [Member]              
Commitments And Contingencies [Line Items]              
Guarantee Obligation Related To Tenant Re-Leasing Costs     25,700,000bxp_GuaranteeObligationRelatedToTenantReLeasingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= bxp_JohnHancockTowerMember		        
Fountain Square [Member]              
Commitments And Contingencies [Line Items]              
Guarantee Obligation Related To Tenant Re-Leasing Costs     700,000bxp_GuaranteeObligationRelatedToTenantReLeasingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= bxp_FountainSquareMember		        
601 Lexington Avenue [Member]              
Commitments And Contingencies [Line Items]              
Coverage For Acts Of Terrorism Under TRIA Covered in Excess of Amount Covered by IXP     $ 250,000,000bxp_CoverageForActsOfTerrorismUnderTriaCoveredInExcessOfAmountCoveredByIxp
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= bxp_SixZeroOneLexingtonAvenueMember