Net gain (loss) on real estate venture transactions including real estate venture formation.

No definition available.

Name:	bdn_NetGainLossOnRealEstateVentureTransactionsIncludingRealEstateVentureFormation
Namespace Prefix:	bdn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of properties contributed to a joint venture

+ References

No definition available.

+ Details

Name:	bdn_Numberofpropertiescontributedtoajointventure
Namespace Prefix:	bdn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Area of a real estate property.

+ References

No definition available.

+ Details

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

- Definition

Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

+ References

No definition available.

+ Details

Name:	us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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://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

- Definition

The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=bdn_CharlottesvilleVAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - PJP Ventures (Details) $ in Thousands		12 Months Ended
	Oct. 29, 2019 USD ($) ft² property	Dec. 31, 2019 USD ($) ft²	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Schedule of Equity Method Investments [Line Items]
Area of real estate property \| ft²		16,711,387
Proceeds from the sale of properties		$ 41,795	$ 324,090	$ 171,860
Net gain on real estate venture transactions		$ 11,639	$ 142,233	$ 80,526
Charlottesville VA \| PJP II, PJP VII, And PJP VII
Schedule of Equity Method Investments [Line Items]
Number of properties contributed to a joint venture \| property	3
Area of real estate property \| ft²	204,347
Sales Price	$ 51,000
Proceeds from the sale of properties	9,100
Net gain on real estate venture transactions	$ 8,000
Minimum \| Charlottesville VA \| PJP II, PJP VII, And PJP VII
Schedule of Equity Method Investments [Line Items]
Ownership percentage	25.00%
Maximum \| Charlottesville VA \| PJP II, PJP VII, And PJP VII
Schedule of Equity Method Investments [Line Items]
Ownership percentage	30.00%