v2.4.0.8

Noncontrolling Interests Redeemable interest in proty partnership (Narrative) (Details) (Fountain Square [Member], USD $) In Millions, unless otherwise specified | 0 Months Ended
--- | ---
Oct. 04, 2012
Fountain Square [Member] |
Noncontrolling Interest [Line Items] |
Aggregate purchase price | $ 385.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt | 211.3
Ownership Percentage | 50.00%
Cash contributed | 87.0
Noncontrolling Interest, Ownership Percentage by Parent | 50.00%
Future Fixed Price to Acquire Remaining Portion of Joint venture | $ 102.0
Fixed Price Option Expiration Date | Jan. 31, 2016

X
- Definition Aggregate purchase price + References No definition available. + Details
Name: | bxp_Aggregatepurchaseprice
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fixed Price Option Expiration Date + References No definition available. + Details
Name: | bxp_FixedPriceOptionExpirationDate
Namespace Prefix: | bxp_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Definition Future Fixed Price to Acquire Remaining Portion of Joint venture + References No definition available. + Details
Name: | bxp_FutureFixedPricetoAcquireRemainingPortionofJointventure
Namespace Prefix: | bxp_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of long-term debt due after one year or the normal operating cycle, if longer, assumed at the acquisition date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6910749&loc=d3e4845-128472 + Details
Name: | us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- 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

X
- 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

X
- Definition The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: 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=31042434&loc=d3e3213-108585 + Details
Name: | us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration