Debt Instrument, Extension Term

No definition available.

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Period Type:	duration

- Definition

Debt Instrument, Issued At a Premium, Percentage Of Face Amount

+ References

No definition available.

+ Details

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Namespace Prefix:	bdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt instrument, number of extensions.

+ References

No definition available.

+ Details

Name:	bdn_DebtInstrumentNumberOfExtensions
Namespace Prefix:	bdn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility, covenant, maximum leverage ratio.

+ References

No definition available.

+ Details

Name:	bdn_LineOfCreditFacilityCovenantMaximumLeverageRatio
Namespace Prefix:	bdn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility, covenant, maximum percent of payments of dividends and distributions.

+ References

No definition available.

+ Details

Name:	bdn_LineOfCreditFacilityCovenantMaximumPercentOfPaymentsOfDividendsAndDistributions
Namespace Prefix:	bdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility, covenant, maximum secured indebtedness to asset value ratio.

+ References

No definition available.

+ Details

Name:	bdn_LineOfCreditFacilityCovenantMaximumSecuredIndebtednessToAssetValueRatio
Namespace Prefix:	bdn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility, covenant, maximum unsecured indebtedness to unencumbered asset value ratio.

+ References

No definition available.

+ Details

Name:	bdn_LineOfCreditFacilityCovenantMaximumUnsecuredIndebtednessToUnencumberedAssetValueRatio
Namespace Prefix:	bdn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility, covenant, minimum fixed charge coverage ratio.

+ References

No definition available.

+ Details

Name:	bdn_LineOfCreditFacilityCovenantMinimumFixedChargeCoverageRatio
Namespace Prefix:	bdn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility, covenant, minimum unencumbered cash flow to interest expense on unsecured debt ratio.

+ References

No definition available.

+ Details

Name:	bdn_LineOfCreditFacilityCovenantMinimumUnencumberedCashFlowToInterestExpenseOnUnsecuredDebtRatio
Namespace Prefix:	bdn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum credit spread on LIBOR based loans.

+ References

No definition available.

+ Details

Name:	bdn_MaximumCreditSpreadOnLIBORBasedLoans
Namespace Prefix:	bdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum debt instrument, basis spread on variable rate.

+ References

No definition available.

+ Details

Name:	bdn_MaximumDebtInstrumentBasisSpreadOnVariableRate
Namespace Prefix:	bdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum credit spread on LIBOR based loans.

+ References

No definition available.

+ Details

Name:	bdn_MinimumCreditSpreadOnLIBORBasedLoans
Namespace Prefix:	bdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- 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

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Incremental percentage increase (decrease) in the stated rate on a debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentInterestRateIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

+ Details

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

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

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt premium.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
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+ Details

Name:	us-gaap_DebtInstrumentUnamortizedPremium
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, before accumulated amortization, of debt issuance costs classified as noncurrent. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

+ Details

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

- Definition

Aggregate amount of interest expense on all borrowings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.7,8)
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=bdn_GuaranteedNotesDue2029Member
Namespace Prefix:
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Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bdn_GuaranteedNotesDue2024Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bdn_A2018CreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_FederalFundsEffectiveSwapRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_UnsecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bdn_SevenYearTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bdn_A600MillionUnsecuredCreditFacilityMember
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DEBT OBLIGATIONS - Narrative (Details)				12 Months Ended
DEBT OBLIGATIONS - Narrative (Details)	Dec. 13, 2018 USD ($)	Dec. 12, 2018	Jul. 17, 2018 USD ($) extension	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Oct. 10, 2019 USD ($)
Guaranteed Notes Due 2029
Debt Instrument [Line Items]
Debt instrument, face amount						$ 100,000,000.0
Debt instrument, interest rate, stated percentage						4.55%
Debt instrument, premium, percentage of face amount						110.058%
Net original issue premium					$ 8,500,000
Guaranteed Notes Due 2024
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage						4.10%
Debt instrument, premium, percentage of face amount						106.315%
Net original issue premium					$ 5,300,000
Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit				$ 0
Long-term debt, weighted average interest rate				1.48%	3.52%
Interest expense borrowings				$ 500,000	$ 4,400,000
Revolving Credit Facility \| 2018 Credit Facility
Debt Instrument [Line Items]
Debt instrument, number of extensions \| extension			2
Debt instrument, extension term duration			6 months
Debt financing costs			$ 2,700,000
Minimum credit Spread on a LIBOR rate loan				0.00%
Maximum credit spread on a LIBOR rate Loan				0.45%
Commitment fee percentage				0.25%
Minimum fixed charge coverage ratio				1.5
Maximum leverage ratio				0.60
Maximum unsecured indebtedness to unencumbered asset value ratio				0.60
Maximum secured indebtedness to total asset value ratio				0.40
Minimum unencumbered cash flow to interest expense on unsecured debt ratio				1.75
Maximum percent of payments of dividends and distributions				95.00%
Revolving Credit Facility \| 2018 Credit Facility \| Minimum
Debt Instrument [Line Items]
Commitment fee percentage				0.125%
Revolving Credit Facility \| 2018 Credit Facility \| Maximum
Debt Instrument [Line Items]
Commitment fee percentage				0.30%
Revolving Credit Facility \| 2018 Credit Facility \| LIBOR
Debt Instrument [Line Items]
Variable interest rate				1.10%
Basis spread on variable rate				1.00%
Revolving Credit Facility \| 2018 Credit Facility \| LIBOR \| Minimum
Debt Instrument [Line Items]
Variable interest rate				0.775%
Revolving Credit Facility \| 2018 Credit Facility \| LIBOR \| Maximum
Debt Instrument [Line Items]
Variable interest rate				1.45%
Revolving Credit Facility \| 2018 Credit Facility \| Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate				0.50%
Unsecured Debt
Debt Instrument [Line Items]
Long-term debt, gross				$ 1,828,610,000	1,828,610,000
Unsecured Debt \| Seven-Year Term Loan - Swapped to fixed
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage	2.87%
Long-term debt, gross	$ 250,000,000.0			$ 250,000,000	250,000,000
Debt instrument, term	7 years			7 years
Decrease in interest rate	(0.55%)
Unsecured Debt \| Seven-Year Term Loan - Swapped to fixed \| LIBOR
Debt Instrument [Line Items]
Variable interest rate	1.25%	1.80%
Unsecured Debt \| $600 million Unsecured Credit Facility
Debt Instrument [Line Items]
Debt instrument, face amount				$ 600,000,000
Long-term debt, gross				$ 0	$ 0
Maximum borrowing capacity			$ 600,000,000.0
Unsecured Debt \| $600 million Unsecured Credit Facility \| LIBOR
Debt Instrument [Line Items]
Variable interest rate				1.10%