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Summary of Quarterly Results (Parenthetical) (Details) $ in Thousands |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Dec. 11, 2018 USD ($) | Dec. 31, 2018 USD ($) | Sep. 30, 2018 USD ($) property | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Quarterly Financial Information [Line Items] |  |  |  |  |  |
Net gain on real estate venture transactions |  |  |  | $ 142,233 | $ 80,526 | $ 20,000
Gain on promoted interest in unconsolidated real estate venture |  |  |  | 28,283 | 0 | 0
BRANDYWINE OPERATING PARTNERSHIP, L.P. |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |
Net gain on real estate venture transactions |  |  |  | 142,233 | 80,526 | 20,000
Gain on promoted interest in unconsolidated real estate venture |  |  |  | $ 28,283 | $ 0 | $ 0
DRA Austin Venture [Member] |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |
Net gain on real estate venture transactions | $ 103,800 | $ 103,800 |  |  |  |
Gain on promoted interest in unconsolidated real estate venture | $ 28,300 | 28,300 |  |  |  |
DRA Austin Venture [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P. |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |
Net gain on real estate venture transactions |  | 103,800 |  |  |  |
Gain on promoted interest in unconsolidated real estate venture |  | $ 28,300 |  |  |  |
Metropolitan Washington, D.C. - Office [Member] |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |
Provision for impairment on assets held for sale |  |  | $ 56,900 |  |  |
Number of properties contributed to a joint venture | property |  |  | 8 |  |  |
Metropolitan Washington, D.C. - Office [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P. |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |
Provision for impairment on assets held for sale |  |  | $ 56,900 |  |  |
Number of properties contributed to a joint venture | property |  |  | 8 |  |  |

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