Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accounts receivable, allowance	$ 3,467	$ 2,373
Accrued rent receivable, allowance	$ 13,645	$ 13,743
Preferred Stock, Shares Authorized	20,000,000	20,000,000
Preferred Stock, Dividend Rate, Percentage	6.90%	6.90%
Preferred Stock, Par or Stated Value Per Share (USD per share)	$ 0.01	$ 0.01
Preferred Stock, Shares Issued	0	4,000,000
Preferred Stock, Shares Outstanding	0	4,000,000
Common Stock, Par or Stated Value Per Share (USD per share)	$ 0.01	$ 0.01
Common Stock, Shares Authorized	400,000,000	400,000,000
Common Stock, Shares, Issued	178,285,236	175,140,760
Common Stock, Shares, Outstanding	178,285,236	175,140,760
Common Shares in Grantor Trust	894,736	899,457
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Accounts receivable, allowance	$ 3,467	$ 2,373
Accrued rent receivable, allowance	$ 13,645	$ 13,743
Preferred Stock, Dividend Rate, Percentage	6.90%	6.90%
Preferred Stock, Shares Issued	0	4,000,000
Preferred Stock, Shares Outstanding	0	4,000,000
Redeemable Limited Partnership Units Issued	1,479,799	1,479,799
Redeemable Limited Partnership Units Outstanding	1,479,799	1,479,799
General Partners' Capital Account, Units Issued	178,285,236	175,140,760
General Partners' Capital Account, Units Outstanding	178,285,236	175,140,760