Costs funded (in percentage)

No definition available.

Name:	bxp_Costsfundedinpercentage
Namespace Prefix:	bxp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Portion of costs funded (in percentage)

+ References

No definition available.

+ Details

Name:	bxp_Portionofcostsfundedinpercentage
Namespace Prefix:	bxp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Portion of project costs covered by a construction loan

+ References

No definition available.

+ Details

Name:	bxp_Portionofprojectcostscoveredbyaconstructionloan
Namespace Prefix:	bxp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Preferred equity funded

+ References

No definition available.

+ Details

Name:	bxp_Preferredequityfunded
Namespace Prefix:	bxp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Unpaid principal balance of the members' notes payable contributed to equity

+ References

No definition available.

+ Details

Name:	bxp_Unpaidprincipalbalanceofthemembersnotespayablecontributedtoequity
Namespace Prefix:	bxp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the amount of gain (loss) on sale of properties during the reporting period gross of the applicable income taxes realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 974
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-15.(a)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=6875705&loc=d3e641549-123027

+ Details

Name:	us-gaap_GainLossOnSaleOfPropertiesBeforeApplicableIncomeTaxes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Carrying amount of the equity interests owned by noncontrolling partners of a limited partnership included in the entity's consolidated financial statements.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestInLimitedPartnerships
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Cash received from the sale of real estate that is held for investment, that is, it is part of an investing activity during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromSaleOfRealEstateHeldforinvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=bxp_SalesforeceTowerformerlyTransbayTowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstatePropertiesAxis=us-gaap_ConsolidatedPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConsolidatedEntitiesAxis=us-gaap_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=bxp_SevensixsevenfifthavenuethegeneralmotorsbuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConsolidationItemsAxis=us-gaap_ConsolidationEliminationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Noncontrolling Interests (Property Partnerships) (Narrative) (Details) - USD ($) $ in Thousands		12 Months Ended
	May 12, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 06, 2017
Noncontrolling Interest [Line Items]
Property partnerships		$ 1,711,445	$ 1,683,760
Proceeds from sales of real estate		455,409	29,810	$ 122,750
Gains on sales of real estate		182,356	7,663	80,606
Boston Properties Limited Partnership
Noncontrolling Interest [Line Items]
Proceeds from sales of real estate		455,409	29,810	122,750
Gains on sales of real estate		190,716	$ 8,240	$ 82,775
Salesforce Tower \| Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Ownership Percentage	5.00%
Portion of project costs covered by a construction loan	50.00%
Portion of costs funded (in percentage)	50.00%
Debt Instrument, Basis Spread on Variable Rate	3.00%
Salesforce Tower \| Boston Properties, Inc. [Member] \| Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Costs funded (in percentage)	2.50%
Preferred equity funded		$ 22,600
767 Fifth Avenue (the general motors building) [Member] \| Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Ownership Percentage by Parent					60.00%
Unpaid principal balance of the members' notes payable contributed to equity					$ 273,900
Property partnerships					109,600
Consolidation, Eliminations [Member] \| 767 Fifth Avenue (the general motors building) [Member] \| Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Unpaid principal balance of the members' notes payable contributed to equity					$ 164,400