Accrued interest payable on construction loan.

No definition available.

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Namespace Prefix:	bdn_
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Balance Type:	credit
Period Type:	instant

- Definition

Debt instrument, maximum borrowing capacity.

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Development Costs - Contemplated Debt Financing

+ References

No definition available.

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Namespace Prefix:	bdn_
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- Definition

Equity method investment summarized financial information debt.

+ References

No definition available.

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- Definition

Equity method investment summarized financial information debt net.

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No definition available.

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- Definition

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

+ References

No definition available.

+ Details

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Number of unconsolidated investments in Real Estate Ventures.

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No definition available.

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- Definition

Number of units in real estate property sold.

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No definition available.

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- Definition

Sale of ownership interest percentage.

+ References

No definition available.

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- Definition

Maturity date of mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Regulation S-X (SX)
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column C))
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Interest rate of mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
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-Subparagraph (SX 210.12-29(Column B))
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- Definition

For an unclassified balance sheet, the amount due from customers or clients for goods or services that have been delivered or sold in the normal course of business, reduced to their estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

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Area of land held.

+ References

No definition available.

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Area of a real estate property.

+ References

No definition available.

+ Details

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This element represents the carrying value of a short-term real estate loan to finance building costs. The funds are disbursed as needed or in accordance with a prearranged plan; generally, a portion of the funds is disbursed at inception and the remainder as construction progresses. The money is repaid on completion of the project, usually from the proceeds of a mortgage loan. The rate is normally higher than the prime rate, and there is usually an origination fee. The effective yield on these loans tends to be high, and the lender has a security interest in the real property. Note that there are separate concepts for the current and noncurrent portions of long-term construction loans.

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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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

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-Subparagraph (SX 210.9-03(16))
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Face (par) amount of debt instrument at time of issuance.

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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-SubTopic 20
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-Paragraph 6
-Subparagraph (a)
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-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-SubTopic 10
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-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
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-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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Period Type:	duration

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

+ References

No definition available.

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- Definition

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

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-Section S99
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-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Period Type:	instant

- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

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-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=115931803&loc=d3e12069-110248

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Net rentable area for properties owned.

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No definition available.

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Amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. Excludes amounts related to receivables held-for-sale.

+ References

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The number of units in a real estate property owned as of the balance sheet date.

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No definition available.

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The cash inflow associated with the sale of 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.

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The cash outflow from repayment of borrowings to finance the cost of construction.

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Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

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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.

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Period Type:

Investment in Unconsolidated Real Estate Ventures (Textual) (Details)					3 Months Ended		9 Months Ended
	Aug. 01, 2018 USD ($)	Jun. 26, 2018 USD ($)	Jan. 10, 2018 USD ($) property	Jan. 05, 2018 USD ($) ft²	Sep. 30, 2018 USD ($) ft² a Real_Estate_Investment Apartment_unit	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) ft² a Real_Estate_Investment Apartment_unit	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method					$ 167,782,000		$ 167,782,000		$ 194,621,000
Accounts receivable					13,871,000		13,871,000		17,938,000
Debt, net					$ 660,041,000		$ 660,041,000		766,420,000
Area of real estate property \| ft²					16,462,764		16,462,764
Net gain on Real Estate Venture transactions					$ 0	$ 13,758,000	$ 37,263,000	$ 28,340,000
Proceeds from real estate venture sales							42,953,000	59,022,000
Evo at Cira Disposition [Member]
Schedule Of Equity Method Investments [Line Items]
Sale of ownership interest percentage			50.00%
Net gain on Real Estate Venture transactions			$ 25,700,000
Number of property units sold \| property			345
Sales Price			$ 197,500,000
Proceeds from real estate venture sales			43,000,000.0
Cost of equity method investment			17,300,000
Philadelphia [Member] \| Pennsylvania [Member] \| Evo at Cira Disposition [Member]
Schedule Of Equity Method Investments [Line Items]
Principal balance of secured loan			$ 110,900,000
Secured Debt [Member]
Schedule Of Equity Method Investments [Line Items]
Real estate property debt					324,886,000		324,886,000		320,107,000
Third Party Management Fees, Labor Reimbursement and Leasing [Member]
Schedule Of Equity Method Investments [Line Items]
Management fees					$ 4,944,000	6,918,000	$ 17,531,000	20,483,000
Office Properties [Member]
Schedule Of Equity Method Investments [Line Items]
Rentable Square Feet \| ft²					38,260		38,260
Area of real estate property \| ft²					13,673,405		13,673,405
Sales Price					$ 2,000,000		$ 2,000,000
Real Estate Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Accounts receivable					1,200,000		1,200,000		$ 900,000
Real Estate Venture [Member] \| Third Party Management Fees, Labor Reimbursement and Leasing [Member]
Schedule Of Equity Method Investments [Line Items]
Management fees					1,400,000	1,700,000	4,000,000.0	4,900,000
Real Estate Venture [Member] \| Lease Commission Income [Member] \| Third Party Management Fees, Labor Reimbursement and Leasing [Member]
Schedule Of Equity Method Investments [Line Items]
Management fees					$ 1,500,000	$ 1,900,000	$ 4,400,000	$ 5,500,000
Unconsolidated Real Estate Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Number of unconsolidated investments in Real Estate Ventures \| Real_Estate_Investment					10		10
Investment in Real Estate Ventures, equity method					$ 167,800,000		$ 167,800,000
Real estate ventures aggregate indebtedness to third parties					$ 664,200,000		$ 664,200,000
Unconsolidated Real Estate Ventures [Member] \| Minimum [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage					25.00%	20.00%	25.00%	20.00%
Unconsolidated Real Estate Ventures [Member] \| Maximum [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage					70.00%	70.00%	70.00%	70.00%
Unconsolidated Real Estate Ventures [Member] \| Six Real Estate Ventures [Member] \| Office Properties [Member]
Schedule Of Equity Method Investments [Line Items]
Number of unconsolidated investments in Real Estate Ventures \| Real_Estate_Investment					6		6
Rentable Square Feet \| ft²					6,600,000		6,600,000
Unconsolidated Real Estate Ventures [Member] \| Two Real Estate Ventures [Member] \| Land Held For Development [Member]
Schedule Of Equity Method Investments [Line Items]
Number of unconsolidated investments in Real Estate Ventures \| Real_Estate_Investment					2		2
Acreage of land \| a					1.4		1.4
Unconsolidated Real Estate Ventures [Member] \| One Real Estate Venture [Member] \| Land Under Active Development [Member]
Schedule Of Equity Method Investments [Line Items]
Number of unconsolidated investments in Real Estate Ventures \| Real_Estate_Investment					1		1
Acreage of land \| a					1.3		1.3
Unconsolidated Real Estate Ventures [Member] \| One Other Real Estate Venture [Member] \| Residential Tower [Member]
Schedule Of Equity Method Investments [Line Items]
Number of unconsolidated investments in Real Estate Ventures \| Real_Estate_Investment					1		1
Number of Property units \| Apartment_unit					321		321
MAP Ground Lease Venture LLC [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage	50.00%
Real estate ventures aggregate indebtedness to third parties	$ 180,800,000
Debt instrument maturity date	Feb. 09, 2019
MAP Ground Lease Venture LLC [Member] \| Secured Debt [Member]
Schedule Of Equity Method Investments [Line Items]
Debt instrument maturity date	Aug. 01, 2023
Indebtedness to third parties, refinanced amount	$ 185,000,000.0
Debt instrument, basis spread on variable rate	2.45%
MAP Ground Lease Venture LLC [Member] \| Maximum [Member] \| Secured Debt [Member]
Schedule Of Equity Method Investments [Line Items]
Effective interest rate	6.00%
1919 Ventures
Schedule Of Equity Method Investments [Line Items]
Ownership percentage		50.00%
Debt, net		$ 44,400,000
Loan interest rate		4.00%
Mortgage loans scheduled maturity date		Jun. 25, 2023
Repayment of construction loan		$ 88,800,000
Construction loan, principal amount		88,600,000
Accrued interest on construction loan		$ 200,000
1919 Ventures \| LCOR/Calstrs [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage		50.00%
1919 Ventures \| Other Assets [Member]
Schedule Of Equity Method Investments [Line Items]
Note receivable		$ 44,400,000
Four Tower Bridge [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage				35.00%
Net gain on Real Estate Venture transactions				$ 11,600,000
Four Tower Bridge [Member] \| Conshohocken [Member] \| Pennsylvania [Member]
Schedule Of Equity Method Investments [Line Items]
Area of real estate property \| ft²				86,021
Real estate property debt				$ 9,700,000
Seven Tower Bridge [Member]
Schedule Of Equity Method Investments [Line Items]
Sale of ownership interest percentage				20.00%
PJP VII [Member]
Schedule Of Equity Method Investments [Line Items]
Real estate property debt					$ 4,200,000		$ 4,200,000
Guarantees, maximum exposure amount					400,000		400,000
4040 Wilson Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Guarantees, maximum exposure amount					41,300,000		41,300,000
Construction loan total borrowing capacity					$ 150,000,000.0		$ 150,000,000.0