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Summary of Significant Accounting Policies - Income Taxes (Textual) (Details) - USD ($) $ in Billions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017
Income Tax Contingency [Line Items] |  |
Distributable Income Minimum Percentage | 90.00% |
Tax Basis of Assets, Cost for Income Tax Purposes | $ 3.3 | $ 3.1
Federal excise tax if sufficient taxable income is not distributed within prescribed time limits | 4.00% |
Excise tax equal to annual amount | 4.00% |
Excise tax, if sum of ordinary income | 85.00% |
Excise tax, if Net capital gain exceeds cash distributions and certain taxes paid | 95.00% |
BRANDYWINE OPERATING PARTNERSHIP, L.P. |  |
Income Tax Contingency [Line Items] |  |
Tax Basis of Assets, Cost for Income Tax Purposes | $ 3.3 | $ 3.1

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- Definition Cost basis of real estate investments for federal income tax purposes for entities with a substantial portion of business acquiring and holding investment real estate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Footnote 6 -Subsection 28 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 970 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Footnote 6)) -URI http://asc.fasb.org/extlink&oid=6590653&loc=d3e638233-123024 + Details
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