Consolidated Statement of Equity (USD $) In Thousands	Total	Common Shares Of Beneficial Interest [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income [Member]	Distributions in Excess of Net Income [Member]	Common Shares Held in Treasury [Member]	Total Liberty Property Trust Shareholders' Equity [Member]	Noncontrolling interest operating partnership-Common [Member]	Noncontrolling interest operating partnership-Preferred [Member]	Noncontrolling interest-consolidated joint ventures [Member]	Liberty Property Limited Partnership [Member]	Liberty Property Limited Partnership [Member] General Partners Equity [Member]	Liberty Property Limited Partnership [Member] Noncontrolling interest operating partnership-Common [Member]	Liberty Property Limited Partnership [Member] Noncontrolling interest operating partnership-Preferred [Member]	Liberty Property Limited Partnership [Member] Noncontrolling interest-consolidated joint ventures [Member]	Common Units [Member]	Common Units [Member] Additional Paid-In Capital [Member]	Common Units [Member] Total Liberty Property Trust Shareholders' Equity [Member]	Common Units [Member] Noncontrolling interest operating partnership-Common [Member]	preferred unit [Member]	preferred unit [Member] Total Liberty Property Trust Shareholders' Equity [Member]	preferred unit [Member] Noncontrolling interest operating partnership-Preferred [Member]
Beginning Balance at Dec. 31, 2011	$ 2,459,756	$ 117	$ 2,617,355	$ (429)	$ (461,498)	$ (51,951)	$ 2,103,594	$ 64,428	$ 287,959	$ 3,775	$ 2,459,756	$ 2,103,594	$ 64,428	$ 287,959	$ 3,775
Net proceeds from the issuance of common shares	42,808	2	42,806				42,808
Net income	107,180				99,006		99,006	3,173	5,001		107,180	99,006	3,173	5,001
Contributions from partners											51,115	51,115
Distributions to partners											(181,613)	(167,421)	(5,501)	(8,691)
Distributions	(181,613)				(167,421)		(167,421)	(5,501)	(8,691)
Noncash compensation	8,307		8,307				8,307
Foreign currency translation adjustment	3,047			2,952			2,952	95			3,047	2,952	95
Redemption of noncontrolling interests - common units											(224,694)			(224,694)		0	1,208	1,208	(1,208)	(224,694)		(224,694)
Redemption of limited partners common units for common shares												1,208	(1,208)
Preferred Stock Redemption Discount	3,689								3,689		3,689			3,689
Ending Balance at Sep. 30, 2012	2,218,480	119	2,669,676	2,523	(529,913)	(51,951)	2,090,454	60,987	63,264	3,775	2,218,480	2,090,454	60,987	63,264	3,775
Beginning Balance at Jun. 30, 2012
Net income	29,898										29,898
Foreign currency translation adjustment	2,245										2,245
Ending Balance at Sep. 30, 2012	$ 2,218,480					$ (51,951)				$ 3,775	$ 2,218,480