v2.4.0.8

Mortgage Notes Payable (Details) (USD $)	9 Months Ended		3 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Mortgages [Member] New Dominion Technology Park, Bldg. Two [Member]	Jul. 01, 2014 Mortgages [Member] New Dominion Technology Park, Bldg. Two [Member]
Debt Instrument [Line Items]
Repayments of Secured Debt	$ 82,030,000	$ 96,750,000	$ 63,000,000
Coupon/Stated Rate				5.55%
Maturity Date			Oct. 01, 2014
Penalty For Early Repayment Of Debt			$ 0

X

- Definition

Penalty For Early Repayment Of Debt

+ References

No definition available.

+ Details

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Namespace Prefix:	bxp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

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- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

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-Subparagraph (SX 210.5-02.22(a)(2))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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X

- 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=31042434&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

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