Name:	bxp_SquareFootageOfSignedLease
Namespace Prefix:	bxp_
Data Type:	xbrli:positiveIntegerItemType
Balance Type:	na
Period Type:	duration

- Definition

Term of Lease Signed (in years)

+ References

No definition available.

+ Details

Name:	bxp_TermofLeaseSignedinyears
Namespace Prefix:	bxp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

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

- Definition

Net rentable area for properties owned.

+ References

No definition available.

+ Details

Name:	us-gaap_NetRentableArea
Namespace Prefix:	us-gaap_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow associated with the purchase of or advances to an equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3213-108585

+ Details

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

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

- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=bxp_BNYTowerHoldingsLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=bxp_OneTwoSixFiveMainOfficeJVLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=bxp_BNYTowerHoldingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=bxp_CompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=bxp_JointventurepartnerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Investments in Unconsolidated Joint Ventures Investments in Unconsolidated Joint Ventures (Narrative) (Details) - Subsequent Event Type [Domain] $ in Thousands			6 Months Ended
	Jun. 26, 2015 USD ($) ft² yr	May. 08, 2015 USD ($) ft² yr	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)
Schedule of Equity Method Investments [Line Items]
Payments to Enter into a Joint Venture Agreement			$ 14,989	$ 47,767
Dock72 at Brooklyn Navy Yard [Member]
Schedule of Equity Method Investments [Line Items]
Net Rentable Area (in sf) \| ft²	670,000
Ownership Percentage			50.00%
Term of Lease Signed (in years) \| yr	20
Square Footage Of Signed Lease \| ft²	222,000
1265 Main Street [Member]
Schedule of Equity Method Investments [Line Items]
Net Rentable Area (in sf) \| ft²		115,000
Ownership Percentage			50.00%
Term of Lease Signed (in years) \| yr		15
Portion of Building Leased (percentage)		100.00%
BNY Tower Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Non refundable option payment	$ 1,000
Company [Member] \| Dock72 at Brooklyn Navy Yard [Member]
Schedule of Equity Method Investments [Line Items]
Payments to Enter into a Joint Venture Agreement	$ 9,100
Ownership Percentage	50.00%
Company [Member] \| 1265 Main Street [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		50.00%
joint venture partner [Member] \| Dock72 at Brooklyn Navy Yard [Member]
Schedule of Equity Method Investments [Line Items]
Payments to Enter into a Joint Venture Agreement	$ 9,100
Ownership Percentage	50.00%
joint venture partner [Member] \| 1265 Main Street [Member]
Schedule of Equity Method Investments [Line Items]
Payments to Enter into a Joint Venture Agreement		$ 9,400
Ownership Percentage		50.00%
Minimum [Member] \| Dock72 at Brooklyn Navy Yard [Member]
Schedule of Equity Method Investments [Line Items]
Ground Lease Term (in years) \| yr	46
Minimum [Member] \| BNY Tower Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Net Rentable Area (in sf) \| ft²	600,000
Maximum [Member] \| Dock72 at Brooklyn Navy Yard [Member]
Schedule of Equity Method Investments [Line Items]
Ground Lease Term (in years) \| yr	96
Maximum [Member] \| BNY Tower Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Net Rentable Area (in sf) \| ft²	1,000,000
Maximum [Member] \| Company [Member] \| 1265 Main Street [Member]
Schedule of Equity Method Investments [Line Items]
Payments to Enter into a Joint Venture Agreement		$ 9,400