Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule of accumulated other comprehensive income (loss) [Line Items]
Accumulated other comprehensive loss	$ (15,918)	$ (6,079)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	(7,338)	(4,499)	7,320
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	(297)	(153)	(28)
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(2,985)	0	0
Accumulated Other Comprehensive Income (Loss) [Member]
Schedule of accumulated other comprehensive income (loss) [Line Items]
Accumulated other comprehensive loss	(15,918)	(6,079)	(1,945)	(9,138)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	(7,338)	(4,499)	7,320
Other Comprehensive Income (Loss) Non-Controlling Interest Consolidated Real Estate Venture Partner's Share of Unrealized (gains) losses on derivative financial statements	187	212	(155)
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	297	153	28
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(2,985)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Schedule of accumulated other comprehensive income (loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(9)	(9)	(9)	(9)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	0	0	0
Other Comprehensive Income (Loss) Non-Controlling Interest Consolidated Real Estate Venture Partner's Share of Unrealized (gains) losses on derivative financial statements	0	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	0	0	0
Derivative Instruments, Gain (Loss) Recognized in Income, Net	0
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Schedule of accumulated other comprehensive income (loss) [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	(7,338)	(4,499)	7,320
Other Comprehensive Income (Loss) Non-Controlling Interest Consolidated Real Estate Venture Partner's Share of Unrealized (gains) losses on derivative financial statements	187	212	(155)
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	297	153	28
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	(15,909)	(6,070)	(1,936)	(9,129)
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(2,985)
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Schedule of accumulated other comprehensive income (loss) [Line Items]
Accumulated other comprehensive loss	(16,452)	(6,426)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	(7,338)	(4,499)	7,320
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	(297)	(153)	(28)
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(2,985)	0	0
BRANDYWINE OPERATING PARTNERSHIP, L.P. | Accumulated Other Comprehensive Income (Loss) [Member]
Schedule of accumulated other comprehensive income (loss) [Line Items]
Accumulated other comprehensive loss	(16,452)	(6,426)	(2,080)	(9,428)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	(7,338)	(4,499)	7,320
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	297	153	28
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(2,985)
BRANDYWINE OPERATING PARTNERSHIP, L.P. | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Schedule of accumulated other comprehensive income (loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(9)	(9)	(9)	(9)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	0	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	0	0	0
Derivative Instruments, Gain (Loss) Recognized in Income, Net	0
BRANDYWINE OPERATING PARTNERSHIP, L.P. | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Schedule of accumulated other comprehensive income (loss) [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	(7,338)	(4,499)	7,320
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	297	153	28
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	(16,443)	(6,417)	(2,071)	(9,419)
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ (2,985)