Income per Common Unit of the Operating Partnership - Dilutive (Details) (Liberty Property Limited Partnership [Member], Stock Option [Member], Common Units [Member]) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Liberty Property Limited Partnership [Member] | Stock Option [Member] | Common Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount of Option Exercises in Period	44	504	841