XML 102 R94.htm IDEA: XBRL DOCUMENT v3.19.3.a.u2

Subsequent Events (Details) $ in Thousands						12 Months Ended
	Feb. 20, 2020 USD ($) ft² Buildings	Feb. 06, 2020 USD ($) shares	Feb. 04, 2020 USD ($) shares	Jan. 28, 2020 USD ($) ft² a Buildings	Sep. 20, 2019 USD ($) ft² a	Dec. 31, 2019 USD ($) shares		Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)	Jan. 31, 2020 shares
Subsequent Event [Line Items]
Common stock, shares issued | shares						154,869,198		154,537,378
Payments to Acquire Equity Method Investments						$ 87,392		$ 345,717	$ 109,015
MYLTIPS 2020 [Member]
Subsequent Event [Line Items]
MYLTIP Value Amortized Into Earnings, Years			four-year
Value of MYTIP to be recognized as expense during the first year of issuance			$ 7,900
Subsequent Event [Member] | MYLTIPS 2020 [Member]
Subsequent Event [Line Items]
Value of MYLTIP Awards			$ 13,700
Subsequent Event [Member] | MYLTIPS 2020 [Member] | NAREIT Office Index adjusted [Member]
Subsequent Event [Line Items]
Target Tier | shares			101,638
Subsequent Event [Member] | MYLTIP 2017 [Member]
Subsequent Event [Line Items]
Value of MYLTIP Awards		$ 17,600
Final awards percentage of target		83.80%
MYLTIP Units forfeited | shares		270,942
Subsequent Event [Member] | Minimum [Member] | MYLTIPS 2020 [Member] | NAREIT Office Index adjusted [Member]
Subsequent Event [Line Items]
Minimum earned awards | shares			0
Subsequent Event [Member] | Maximum [Member] | MYLTIPS 2020 [Member] | NAREIT Office Index adjusted [Member]
Subsequent Event [Line Items]
Maximum Earned Awards | shares			203,278
Subsequent Event [Member] | Restricted Stock [Member]
Subsequent Event [Line Items]
Common stock, shares issued | shares										24,503
Subsequent Event [Member] | LTIP Units [Member]
Subsequent Event [Line Items]
LTIP units issued (in shares) | shares			196,927
New Dominion Technology Park [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Contractual Sales Price	$ 256,000
number of buildings | Buildings	2
Net Rentable Area (in sf) | ft²	493,000
Gateway Commons Complex [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Ownership Percentage				50.00%
number of buildings | Buildings				3
Net Rentable Area (in sf) | ft²				768,000
Payments to Acquire Equity Method Investments				$ 350,000
Platform 16
Subsequent Event [Line Items]
Ownership Percentage					55.00%	55.00%	[1]
Net Rentable Area (in sf) | ft²					1,100,000
Finance lease fixed purchase price					$ 134,800
Area of Land | a					5.6
Payments to Acquire Equity Method Investments					$ 28,200
Platform 16 | Subsequent Event [Member]
Subsequent Event [Line Items]
Ownership Percentage				55.00%
Net Rentable Area (in sf) | ft²				1,100,000
Finance lease fixed purchase price				$ 134,800
Prepaid purchase price				$ 15,000
Area of Land | a				5.6
Joint Venture Partner [Member] | Gateway Commons Complex [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Ownership Percentage				50.00%
number of buildings | Buildings				3
Payments to Acquire Equity Method Investments				$ 280,800
Future payment to acquire interest in equity method investment				$ 69,200
Joint Venture Partner [Member] | Platform 16
Subsequent Event [Line Items]
Ownership Percentage					45.00%
Payments to Acquire Equity Method Investments					$ 23,100
425 Fourth Street | Subsequent Event [Member]
Subsequent Event [Line Items]
Net Rentable Area (in sf) | ft²				804,000
Aggregate purchase price				$ 134,100
Future Office Building [Member] | Platform 16 | Subsequent Event [Member]
Subsequent Event [Line Items]
Net Rentable Area (in sf) | ft²				390,000
[1] This entity is a VIE (See Note 1).

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

Contractual Sales Price

+ References

No definition available.

+ Details

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

X

- Definition

Final awards percentage of target

+ References

No definition available.

+ Details

Name:	bxp_Finalawardspercentageoftarget
Namespace Prefix:	bxp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Finance Lease fixed purchase price

+ References

No definition available.

+ Details

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

X

- Definition

Future payment to acquire interest in equity method investment

+ References

No definition available.

+ Details

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

X

- Definition

LTIP units issued

+ References

No definition available.

+ Details

Name:	bxp_LtipUnitsIssued
Namespace Prefix:	bxp_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

X

- Definition

MYLTIP Units Forfeited

+ References

No definition available.

+ Details

Name:	bxp_MYLTIPUnitsForfeited
Namespace Prefix:	bxp_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

X

- Definition

MYLTIP Value Amortized Into Earnings, Years

+ References

No definition available.

+ Details

Name:	bxp_MYLTIPValueAmortizedIntoEarningsYears
Namespace Prefix:	bxp_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Maximum Earned Awards

+ References

No definition available.

+ Details

Name:	bxp_MaximumEarnedAwards
Namespace Prefix:	bxp_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Minimum earned awards

+ References

No definition available.

+ Details

Name:	bxp_Minimumearnedawards
Namespace Prefix:	bxp_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

X

- Definition

number of buildings

+ References

No definition available.

+ Details

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

X

- Definition

Target MYLTIPs Earned (in shares)

+ References

No definition available.

+ Details

Name:	bxp_TargetMYLTIPsEarnedinshares
Namespace Prefix:	bxp_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Value of MYLTIP Awards

+ References

No definition available.

+ Details

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

X

- Definition

Value of MYTIP to be recognized as expense during the first year of issuance

+ References

No definition available.

+ Details

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

X

- Definition

Area of land held.

+ References

No definition available.

+ Details

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

X

- Definition

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_CommonStockSharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

X

- 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

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

X

- 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

X

- Definition

Amount of asset related to consideration paid in advance for other costs that provide economic benefits within a future period of one year or the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6676-107765

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6787-107765

+ Details

Name:	us-gaap_OtherPrepaidExpenseCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

+ Details

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

X

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

X

- Details

Name:	bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis=bxp_TwothousandtwentyMYLTIPSMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	bxp_PerformanceIndexAxis=bxp_NareitOfficeIndexAdjustedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis=bxp_MYLTIPtwothousandseventeenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_RestrictedStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementClassOfStockAxis=bxp_LTIPUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=bxp_NewDominionTechnologyParkMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=bxp_GatewayCommonsComplexMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=bxp_PlatformSixteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=bxp_FourHundredtwentyfiveFourthStreetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=bxp_FutureOfficeBuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: