Beneficiaries Equity of the Parent Company (Textual) (Details) - USD ($)				12 Months Ended
	Dec. 07, 2017	Apr. 11, 2017	Jan. 10, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 22, 2015
Class of Stock [Line Items]
Dividends, Common Stock	$ 32,400,000
Dividends payable, date to be paid	Jan. 23, 2018
Dividends payable, date of record	Jan. 09, 2018
Preferred share redemption charge				$ 3,181,000	$ 0	$ 0
Authorized Amount							$ 100,000,000
Repurchased and Retired, Shares				0	0	5,209,437
Share Price						$ 12.90
Repurchased and Retired, Value						$ 67,325,000
Common stock price per share				$ 0.01	$ 0.01
Common Stock, Shares Authorized				400,000,000	400,000,000
Upfront costs				$ 499,000		$ 105,000
Common shares issued under offering program					0	0
Cash proceeds, net of issuance costs				$ 51,225,000	$ 0	$ 0
Offering Program [Member]
Class of Stock [Line Items]
Common Stock, Shares Authorized			16,000,000
Upfront costs			$ 200,000
Common shares issued under offering program				2,858,991	0	0
Weighted average price per share				$ 18.19
Cash proceeds, net of issuance costs				$ 51,200,000
Common shares remain available for future issuance				13,141,009
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Class of Stock [Line Items]
Dividends, Common Stock	$ 32,400,000
Dividends payable, date to be paid	Jan. 23, 2018
Dividends payable, date of record	Jan. 09, 2018
Preferred share redemption charge				$ 3,181,000	$ 0	$ 0
Repurchase program, number of common unit retired for each common share repurchased				1
Cash proceeds, net of issuance costs				$ 51,225,000	$ 0	$ 0
BRANDYWINE OPERATING PARTNERSHIP, L.P. | Series E Preferred Stock [Member]
Class of Stock [Line Items]
Redemption outstanding shares		4,000,000
Redemption price per share		$ 25.51
Accrued dividends paid in cash		$ 2,000,000
Preferred share redemption charge		$ 3,200,000
Dividend Declared [Member]
Class of Stock [Line Items]
Dividends Payable, Amount Per Share	$ 0.18
Dividend Declared [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Class of Stock [Line Items]
Dividends Payable, Amount Per Share	$ 0.18
Redeemable Common Limited Partnership Units [Member]
Class of Stock [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share				1,479,799	1,479,799	1,535,102