Organization of the Parent Company and The Operating Partnership	12 Months Ended
Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP	1. ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP The Parent Company is a self-administered and self-managed real estate investment trust (“REIT”) that provides leasing, property management, development, redevelopment, acquisition and other tenant-related services for a portfolio of office, residential, retail and mixed-use properties. The Parent Company owns its assets and conducts its operations through the Operating Partnership and subsidiaries of the Operating Partnership. The Parent Company is the sole general partner of the Operating Partnership and, as of December 31, 2017, owned a 99.2% interest in the Operating Partnership. The Parent Company’s common shares of beneficial interest are publicly traded on the New York Stock Exchange under the ticker symbol “BDN.” As of December 31, 2017, the Company owned 93 properties that contain an aggregate of approximately 16.4 million net rentable square feet and consist of 81 office properties, five mixed-use properties, one retail property (87 properties, collectively the “Core Properties”), two development properties and four redevelopment properties (collectively, the “Properties”). In addition, as of December 31, 2017, the Company owned interests in 13 unconsolidated real estate ventures (collectively, the “Real Estate Ventures”), seven of which own properties that contain approximately 6.7 million net rentable square feet of office space; three of which own, in aggregate, 4.4 acres of land held for development; one that owns 1.3 acres in active development; and two that own residential towers that contain 345 and 321 apartment units, respectively. Subsequent to December 31, 2017, the Company completed transactions that reduced our interests in Real Estate Ventures and, as of the date of this Form 10-K, the Company owns interests in ten Real Estate Ventures. See Note 20, “Subsequent Events,” to the consolidated financial statements for further information. In addition to the Core Properties, as of December 31, 2017, the Company owned land held for development, comprised of 212 acres of undeveloped land, of which 13.1 acres were held for sale, and held options to purchase approximately 60 additional acres of undeveloped land. As of December 31, 2017, the total potential development that these land parcels could support, including the parcels under option, under current zoning and entitlements, amounted to an estimated 14.8 million square feet, of which 0.1 million square feet relates to the 13.1 acres held for sale. The Properties and the properties owned by the Real Estate Ventures are located in or near Philadelphia, Pennsylvania; Metropolitan Washington, D.C.; Southern New Jersey; Richmond, Virginia; Wilmington, Delaware and Austin, Texas. In addition to managing properties that the Company owns, as of December 31, 2017, the Company was managing approximately 8.8 million net rentable square feet of office and industrial properties for third parties and Real Estate Ventures. All references to building square footage, rentable square feet, acres, occupancy percentage the number of buildings and tax basis are unaudited. The Company conducts its third-party real estate management services business primarily through six management companies (collectively, the “Management Companies”): Brandywine Realty Services Corporation (“BRSCO”), BTRS, Inc. (“BTRS”), Brandywine Properties I Limited, Inc. (“BPI”), BDN Brokerage, LLC (“BBL”), Brandywine Properties Management, L.P. (“BPM”) and Brandywine Brokerage Services, LLC (“BBS”). BRSCO, BTRS and BPI are each a taxable REIT subsidiary. As of December 31, 2017, the Operating Partnership owns, directly and indirectly, 100% of each of BRSCO, BTRS, BPI, BBL, BPM and BBS. As of December 31, 2017, the Management Companies were managing properties containing an aggregate of approximately 25.2 million net rentable square feet, of which approximately 16.4 million net rentable square feet related to Properties owned by the Company and approximately 8.8 million net rentable square feet related to properties owned by third parties and Real Estate Ventures.

1. ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP

The Parent Company is a self-administered and self-managed real estate investment trust (“REIT”) that provides leasing, property management, development, redevelopment, acquisition and other tenant-related services for a portfolio of office, residential, retail and mixed-use properties. The Parent Company owns its assets and conducts its operations through the Operating Partnership and subsidiaries of the Operating Partnership. The Parent Company is the sole general partner of the Operating Partnership and, as of December 31, 2017, owned a 99.2% interest in the Operating Partnership. The Parent Company’s common shares of beneficial interest are publicly traded on the New York Stock Exchange under the ticker symbol “BDN.”

As of December 31, 2017, the Company owned 93 properties that contain an aggregate of approximately 16.4 million net rentable square feet and consist of 81 office properties, five mixed-use properties, one retail property (87 properties, collectively the “Core Properties”), two development properties and four redevelopment properties (collectively, the “Properties”). In addition, as of December 31, 2017, the Company owned interests in 13 unconsolidated real estate ventures (collectively, the “Real Estate Ventures”), seven of which own properties that contain approximately 6.7 million net rentable square feet of office space; three of which own, in aggregate, 4.4 acres of land held for development; one that owns 1.3 acres in active development; and two that own residential towers that contain 345 and 321 apartment units, respectively. Subsequent to December 31, 2017, the Company completed transactions that reduced our interests in Real Estate Ventures and, as of the date of this Form 10-K, the Company owns interests in ten Real Estate Ventures. See Note 20, “Subsequent Events,” to the consolidated financial statements for further information.

In addition to the Core Properties, as of December 31, 2017, the Company owned land held for development, comprised of 212 acres of undeveloped land, of which 13.1 acres were held for sale, and held options to purchase approximately 60 additional acres of undeveloped land. As of December 31, 2017, the total potential development that these land parcels could support, including the parcels under option, under current zoning and entitlements, amounted to an estimated 14.8 million square feet, of which 0.1 million square feet relates to the 13.1 acres held for sale. The Properties and the properties owned by the Real Estate Ventures are located in or near Philadelphia, Pennsylvania; Metropolitan Washington, D.C.; Southern New Jersey; Richmond, Virginia; Wilmington, Delaware and Austin, Texas. In addition to managing properties that the Company owns, as of December 31, 2017, the Company was managing approximately 8.8 million net rentable square feet of office and industrial properties for third parties and Real Estate Ventures.

All references to building square footage, rentable square feet, acres, occupancy percentage the number of buildings and tax basis are unaudited.

The Company conducts its third-party real estate management services business primarily through six management companies (collectively, the “Management Companies”): Brandywine Realty Services Corporation (“BRSCO”), BTRS, Inc. (“BTRS”), Brandywine Properties I Limited, Inc. (“BPI”), BDN Brokerage, LLC (“BBL”), Brandywine Properties Management, L.P. (“BPM”) and Brandywine Brokerage Services, LLC (“BBS”). BRSCO, BTRS and BPI are each a taxable REIT subsidiary. As of December 31, 2017, the Operating Partnership owns, directly and indirectly, 100% of each of BRSCO, BTRS, BPI, BBL, BPM and BBS. As of December 31, 2017, the Management Companies were managing properties containing an aggregate of approximately 25.2 million net rentable square feet, of which approximately 16.4 million net rentable square feet related to Properties owned by the Company and approximately 8.8 million net rentable square feet related to properties owned by third parties and Real Estate Ventures.