v2.4.0.8

Commitments And Contingencies (Details) (USD $) | 6 Months Ended
--- | ---
Jun. 30, 2013
Commitments And Contingencies [Line Items] |
Letter of credit and performance obligations | $ 13,900,000
Property insurance program per occurrence limits | 1,000,000,000
Per occurrence limit for NBCR Coverage | 1,000,000,000
Value of program trigger | 100,000,000
Coinsurance of program trigger | 15.00%
Deductible in insurance as a percentage of the value of the affected property, San Francisco | 5.00%
Per occurrence limit of the earthquake insurance which covers San Francisco region | 120,000,000
Annual aggregate limit of the earthquake insurance which covers San Francisco region | 120,000,000
Amount of earthquake insurance provided by IXP, LLC as direct insurer San Francisco | 20,000,000
Earthquake Coverage Included in Builders Risk Policy for 680 Folsom | 20,000,000
Earthquake Coverage Included In Builders Risk Policy For 535 Mission | 15,000,000
Operating partnership guarantee to cover liabilities of IXP | 20,000,000
767 Venture, LLC [Member] |
Commitments And Contingencies [Line Items] |
Maximum funding obligation | 28,200,000
Property insurance program per occurrence limits | 1,625,000,000
Coverage for acts of Terrorism certified under TRIA in excess of amount provided by NYXP, LLC, as a direct insurer | 1,375,000,000
Coverage for acts of terrorism certified under TRIA | 250,000,000
John Hancock Tower [Member] |
Commitments And Contingencies [Line Items] |
Guarantee Obligation Related To Tenant Re-Leasing Costs | 4,200,000
601 Lexington Avenue [Member] |
Commitments And Contingencies [Line Items] |
Coverage For Acts Of Terrorism Under TRIA Covered in Excess of Amount Covered by IXP | $ 250,000,000

X
- Definition Amount Of Earthquake Insurance Provided By IXP LLC As Direct Insurer San Francisco. + References No definition available. + Details
Name: | bxp_AmountOfEarthquakeInsuranceProvidedByIxpLlcAsDirectInsurerSanFrancisco
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Annual Aggregate Limit Of Earth Quake Insurance San Francisco + References No definition available. + Details
Name: | bxp_AnnualAggregateLimitOfEarthQuakeInsuranceSanFrancisco
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | bxp_CommitmentsAndContingenciesLineItems
Namespace Prefix: | bxp_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The property insurance program per occurrence limits for 767 Fifth Avenue are $1.625 billion, including coverage for acts of terrorism certified under TRIA, with $1.375 billion of coverage for losses in excess of $250 million being provided by NYXP, LLC, as a direct insurer. + References No definition available. + Details
Name: | bxp_CoverageForActsOfTerrorismCertifiedUnderTriaProvidedByNyxpLlcAsDirectInsurer
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Coverage For Acts Of Terrorism Under TRIA + References No definition available. + Details
Name: | bxp_CoverageForActsOfTerrorismUnderTria
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Coverage For Acts Of Terrorism Under TRIA Covered in Excess of Amount Covered by IXP + References No definition available. + Details
Name: | bxp_CoverageForActsOfTerrorismUnderTriaCoveredInExcessOfAmountCoveredByIxp
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Earthquake Coverage Included In Builders Risk Policy For 535 Mission + References No definition available. + Details
Name: | bxp_EarthquakeCoverageIncludedInBuildersRiskPolicyFor535Mission
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Earthquake Coverage Included in Builders Risk Policy for 680 Folsom + References No definition available. + Details
Name: | bxp_EarthquakeCoverageIncludedInBuildersRiskPolicyFor680Folsom
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Earthquake Deductible Insurance Percentage Of Value Of The Affected Property San Francisco + References No definition available. + Details
Name: | bxp_EarthquakeDeductibleInsurancePercentageOfValueOfAffectedPropertySanFrancisco
Namespace Prefix: | bxp_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Guarantee Obligation Related To Tenant Re-Leasing Costs + References No definition available. + Details
Name: | bxp_GuaranteeObligationRelatedToTenantReLeasingCosts
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Insurance Policy Limit + References No definition available. + Details
Name: | bxp_InsurancePolicyLimit
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Letter Of Credit And Performance Obligation + References No definition available. + Details
Name: | bxp_LetterOfCreditAndPerformanceObligation
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Operating partnership guarantee to cover liabilities of subsidiary + References No definition available. + Details
Name: | bxp_OperatingPartnershipGuaranteeToCoverLiabilitiesOfSubsidiary
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Per occurrence limit for NBCR Coverage + References No definition available. + Details
Name: | bxp_PerOccurrenceLimitForNbcrCoverage
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Per Occurrence Limit Of Earth Quake Insurance San Francisco + References No definition available. + Details
Name: | bxp_PerOccurrenceLimitOfEarthQuakeInsuranceSanFrancisco
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Program Trigger Coinsurance + References No definition available. + Details
Name: | bxp_ProgramTriggerCoinsurance
Namespace Prefix: | bxp_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Program Trigger Value + References No definition available. + Details
Name: | bxp_ProgramTriggerValue
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248 + Details
Name: | us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant