XML 55 R40.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Commitments And Contingencies (Details) - USD ($) $ in Millions | 9 Months Ended | 12 Months Ended |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2018 | Dec. 31, 2009 | Sep. 13, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Jan. 10, 2014
Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |
Letter of credit and performance obligations | $ 7.8 |  |  |  |  |  |  |
Property insurance program per occurrence limits | 1,000.0 |  |  |  |  |  |  |
Per occurrence limit for NBCR Coverage | 1,000.0 |  |  |  |  |  |  |
Value of program trigger | $ 160.0 |  |  |  |  |  |  |
Coinsurance of program trigger | 18.00% |  |  |  |  |  |  |
Deductible in insurance as a percentage of the value of the affected property, San Francisco and Los Angeles | 3.00% |  |  |  |  |  |  |
Per occurrence limit of the earthquake insurance which covers San Francisco and Los Angeles regions | $ 240.0 |  |  |  |  |  |  |
Annual aggregate limit of the earthquake insurance which covers San Francisco and Los Angeles regions | 240.0 |  |  |  |  |  |  |
Amount of earthquake insurance provided by IXP, LLC as direct insurer San Francisco and Los Angeles | 20.0 |  |  |  |  |  |  |
767 Venture, LLC [Member] |  |  |  |  |  |  |  |
Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |
Maximum funding obligation | 126.4 |  |  |  |  |  |  |
Property insurance program per occurrence limits | 1,625.0 |  |  |  |  |  |  |
Lehman [Member] |  |  |  |  |  |  |  |
Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |
Bankruptcy claim, amount filed by general creditor |  | $ 45.3 |  |  |  |  |  |
Bankruptcy claim amount allowed by court to creditor |  |  |  |  |  |  |  | $ 45.2
Bankruptcy Claims, Amount of Claims Settled |  |  | $ 0.3 | $ 0.4 | $ 1.4 | $ 8.1 | $ 7.7 |
Bankruptcy remaining claim amount allowed by court to creditor | 27.2 |  |  |  |  |  |  |
601 Lexington Avenue [Member] |  |  |  |  |  |  |  |
Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |
Coverage For Acts Of Terrorism Under TRIA Covered in Excess of Amount Covered by IXP | 250.0 |  |  |  |  |  |  |
Boston Properties Limited Partnership |  |  |  |  |  |  |  |
Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |
Operating partnership guarantee to cover liabilities of IXP | $ 20.0 |  |  |  |  |  |  |

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

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

X
- Definition Bankruptcy claim amount allowed by court to creditor + References No definition available. + Details
Name: | bxp_Bankruptcyclaimamountallowedbycourttocreditor
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Bankruptcy claim, amount filed by general creditor + References No definition available. + Details
Name: | bxp_Bankruptcyclaimamountfiledbygeneralcreditor
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Bankruptcy remaining claim amount allowed by court to creditor + References No definition available. + Details
Name: | bxp_Bankruptcyremainingclaimamountallowedbycourttocreditor
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Commitments And Contingencies [Line Items] + References No definition available. + Details
Name: | bxp_CommitmentsAndContingenciesLineItems
Namespace Prefix: | bxp_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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 Deductible Insurance Percentage Of Value Of The Affected Property San Francisco and Los Angeles + References No definition available. + Details
Name: | bxp_EarthquakeDeductibleInsurancePercentageOfValueOfTheAffectedPropertySanFranciscoandLosAngeles
Namespace Prefix: | bxp_
Data Type: | num:percentItemType
Balance Type: | na
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 and Los Angeles + References No definition available. + Details
Name: | bxp_PerOccurrenceLimitOfEarthQuakeInsuranceSanFranciscoandLosAngeles
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 Amount of bankruptcy claim settled. + References No definition available. + Details
Name: | us-gaap_BankruptcyClaimsAmountOfClaimsSettled
Namespace Prefix: | us-gaap_
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=82913245&loc=d3e12069-110248 + Details
Name: | us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=bxp_SevenSixSevenVentureLlcMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GainContingenciesByNatureAxis=bxp_LehmanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=bxp_SixZeroOneLexingtonAvenueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConsolidatedEntitiesAxis=us-gaap_SubsidiariesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |