Summary of Significant Accounting Policies Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Contingency [Line Items]
Increase In Revenue Due To Amortization Of Deferred Rent	$ 2,400,000	$ 2,400,000	$ 2,400,000
Distributable Income Minimum Percentage	90.00%
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%
Tax Basis of Assets, Cost for Income Tax Purposes	3,700,000,000	4,000,000,000
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Income Tax Contingency [Line Items]
Tax Basis of Assets, Cost for Income Tax Purposes	$ 3,700,000,000	$ 4,000,000,000