Construction Loan Facility Borrowing Capacity

No definition available.

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

- Definition

Gain on Consolidation of Joint Ventures

+ References

No definition available.

+ Details

Name:	bxp_GainonConsolidationofJointVentures
Namespace Prefix:	bxp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Ground Lease Term (in years)

+ References

No definition available.

+ Details

Name:	bxp_GroundLeaseTerminyears
Namespace Prefix:	bxp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Non refundable option payment

+ References

No definition available.

+ Details

Name:	bxp_Nonrefundableoptionpayment
Namespace Prefix:	bxp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Number of Joint Venture Partners

+ References

No definition available.

+ Details

Name:	bxp_NumberofJointVenturePartners
Namespace Prefix:	bxp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Portion of Building Leased (percentage)

+ References

No definition available.

+ Details

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

- Definition

Square Footage Of Signed Lease.

+ References

No definition available.

+ Details

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

This element represents the carrying value of a short-term real estate loan to finance building costs. The funds are disbursed as needed or in accordance with a prearranged plan; generally, a portion of the funds is disbursed at inception and the remainder as construction progresses. The money is repaid on completion of the project, usually from the proceeds of a mortgage loan. The rate is normally higher than the prime rate, and there is usually an origination fee. The effective yield on these loans tends to be high, and the lender has a security interest in the real property. Note that there are separate concepts for the current and noncurrent portions of long-term construction loans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 20
-Article 5

+ Details

Name:	us-gaap_ConstructionLoan
Namespace Prefix:	us-gaap_
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

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

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12317-112629

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12355-112629

+ Details

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

- 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

The cash outflow to repay long-term debt that is wholly or partially secured by collateral. Excludes repayments of tax exempt secured debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3291-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

Name:	us-gaap_RepaymentsOfSecuredDebt
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_OneTwoSixFiveMainOfficeJVLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=bxp_HubonCausewayMember
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:	dei_LegalEntityAxis=bxp_CompanyMember
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:

- Details

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

Investment in unconsolidated Joint Ventures (Narrative) (Details) $ in Thousands				3 Months Ended	12 Months Ended
	Jun. 26, 2015 USD ($) ft² yr	May. 08, 2015 USD ($) ft² yr	May. 31, 2013 partners	Sep. 30, 2015 USD ($) ft²	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 22, 2015 ft²	Oct. 22, 2015 ft²	Sep. 22, 2015 ft²
Schedule of Equity Method Investments [Line Items]
Payments to Acquire Equity Method Investments					$ 38,207	$ 52,052	$ 0
Gains (losses) from early extinguishments of debt					(22,040)	(10,633)	122
Repayments of Secured Debt					54,801	87,758	80,311
Gain on consolidation of joint ventures					$ 0	$ 0	$ 385,991
1265 Main Office JV LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage					50.00%
Net Rentable Area \| ft²		115,000
Term of Lease Signed (in years) \| yr		15
Portion of Building Leased (percentage)		100.00%
767 Fifth Avenue (the General Motors Building)
Schedule of Equity Method Investments [Line Items]
Number of Joint Venture Partners \| partners			2
Annapolis Junction Building Eight [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage								50.00%
Net Rentable Area \| ft²								126,000
Annapolis Junction Building Seven [Member]
Schedule of Equity Method Investments [Line Items]
Net Rentable Area \| ft²										127,000
BNY Tower Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage					50.00%
Net Rentable Area \| ft²	670,000
Term of Lease Signed (in years) \| yr	20
Square Footage Of Signed Lease \| ft²	222,000
BNY Tower Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Non refundable option payment	$ 1,000
Annapolis Junction Building Six [Member]
Schedule of Equity Method Investments [Line Items]
Net Rentable Area \| ft²				119,000
Construction Loan Facility Borrowing Capacity				$ 15,900
Debt Instrument, Basis Spread on Variable Rate				2.25%
Construction Loan				$ 13,400
Hub on Causeway [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage									50.00%
Net Rentable Area \| ft²									385,000
joint venture partner [Member] \| 1265 Main Office JV LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		50.00%
Payments to Acquire Equity Method Investments		$ 9,400
joint venture partner [Member] \| BNY Tower Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	50.00%
Payments to Acquire Equity Method Investments	$ 9,100
Company [Member] \| 1265 Main Office JV LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		50.00%
Company [Member] \| Annapolis Junction Building Seven [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage										50.00%
Company [Member] \| BNY Tower Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	50.00%
Payments to Acquire Equity Method Investments	$ 9,100
Company [Member] \| Annapolis Junction Building Six [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage				50.00%
Maximum [Member] \| BNY Tower Holdings LLC [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 \| ft²	1,000,000
Maximum [Member] \| Company [Member] \| 1265 Main Office JV LLC [Member]
Schedule of Equity Method Investments [Line Items]
Payments to Acquire Equity Method Investments		$ 9,400
Minimum [Member] \| BNY Tower Holdings LLC [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 \| ft²	600,000