Document and Entity Information	9 Months Ended
	Sep. 30, 2012	Oct. 30, 2012
Entity Registrant Name	LIBERTY PROPERTY TRUST
Entity Central Index Key	0000921112
Document Type	10-Q
Document Period End Date	Sep. 30, 2012
Amendment Flag	false
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		118,241,192
Liberty Property Limited Partnership [Member]
Entity Registrant Name	LIBERTY PROPERTY LIMITED PARTNERSHIP
Entity Central Index Key	0000921113