Accounting for the Impairment or Disposal of Long-Lived Assets - Results of Operations for the Properties Held for Sale and Disposed (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	$ 58,145	$ 93,456	$ 115,486
Operating expenses	(25,694)	(38,313)	(41,882)
Interest expense	(9,028)	(15,320)	(17,767)
Depreciation and amortization	(13,166)	(23,307)	(25,230)
Income before property dispositions	10,257	16,516	30,607
Gain on property dispositions	60,582	6,857	17,859
Net Income	70,839	23,373	48,466
Liberty Property Limited Partnership [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on property dispositions	$ 60,582	$ 6,857	$ 17,859