Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012 Reportable_Segments	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Number of reportable segments									7
Real estate investments, at cost:
Operating properties	$ 4,726,169				$ 4,793,080				$ 4,726,169	$ 4,793,080	$ 4,834,111
Construction-in-progress	48,950				25,083				48,950	25,083	33,322
Land inventory	102,439				109,008				102,439	109,008	110,055
Total revenue	142,463	140,383	137,576	139,411	141,486	139,401	139,249	141,617	559,833	561,753	540,432
Property operating expenses, real estate taxes and third party management expenses									220,392	226,838	221,087
Net operating income									339,441	334,915	319,345
Pennsylvania Suburbs [Member]
Real estate investments, at cost:
Operating properties	1,178,730				1,218,071				1,178,730	1,218,071	1,199,957
Total revenue									151,784	150,611	144,792
Property operating expenses, real estate taxes and third party management expenses									53,392	55,558	59,537
Net operating income									98,392	95,053	85,255
Philadelphia CBD [Member]
Real estate investments, at cost:
Operating properties	988,590				953,870				988,590	953,870	911,354
Total revenue									131,594	125,366	92,110
Property operating expenses, real estate taxes and third party management expenses									50,790	48,832	37,890
Net operating income									80,804	76,534	54,220
Metropolitan, D.C. [Member]
Real estate investments, at cost:
Operating properties	1,193,200				1,255,803				1,193,200	1,255,803	1,359,776
Total revenue									107,656	119,255	128,823
Property operating expenses, real estate taxes and third party management expenses									41,487	45,136	46,104
Net operating income									66,169	74,119	82,719
New Jersey/ Delaware [Member]
Real estate investments, at cost:
Operating properties	546,644				545,657				546,644	545,657	568,413
Total revenue									82,395	80,894	87,011
Property operating expenses, real estate taxes and third party management expenses									37,968	40,218	43,780
Net operating income									44,427	40,676	43,231
Richmond, Virginia [Member]
Real estate investments, at cost:
Operating properties	309,923				307,698				309,923	307,698	294,406
Total revenue									35,701	36,789	36,032
Property operating expenses, real estate taxes and third party management expenses									14,485	14,739	14,008
Net operating income									21,216	22,050	22,024
Austin, Texas [Member]
Real estate investments, at cost:
Operating properties	285,346				257,694				285,346	257,694	254,019
Total revenue									32,380	30,894	32,050
Property operating expenses, real estate taxes and third party management expenses									13,952	13,058	13,399
Net operating income									18,428	17,836	18,651
California [Member]
Real estate investments, at cost:
Operating properties	223,736				254,287				223,736	254,287	246,186
Total revenue									20,005	19,192	20,414
Property operating expenses, real estate taxes and third party management expenses									10,050	10,483	10,827
Net operating income									9,955	8,709	9,587
Corporate [Member]
Real estate investments, at cost:
Operating properties	0				0				0	0	0
Construction-in-progress	48,950				25,083				48,950	25,083	33,322
Land inventory	102,439				109,008				102,439	109,008	110,055
Total revenue									(1,682)	(1,248)	(800)
Property operating expenses, real estate taxes and third party management expenses									(1,732)	(1,186)	(4,458)
Net operating income									50	(62)	3,658
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Real estate investments, at cost:
Operating properties	4,726,169				4,793,080				4,726,169	4,793,080
Construction-in-progress	48,950				25,083				48,950	25,083
Land inventory	102,439				109,008				102,439	109,008
Total revenue									$ 559,833	$ 561,753	$ 540,432