Income per Common Unit of the Operating Partnership - Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income (Numerator) [Abstract]
Income from continuing operations net of noncontrolling interest - consolidated joint ventures	$ 48,595	$ 56,487	$ 104,885	$ 136,460
Income from discontinued operations	103,971	3,125	209,945	17,942
Net income available to common shareholders or unitholders	$ 150,143	$ 59,539	$ 309,938	$ 153,982
Weighted Average Units (Denominator) [Abstract]
Weighted Average Number of Shares or Units Outstanding, Basic	147,324	146,811	147,241	146,678
Dilutive units for long-term compensation plans	947	785	919	752
Weighted Average Number of Shares or Units Outstanding, Diluted	148,271	147,596	148,160	147,430
Liberty Property Limited Partnership [Member]
Income (Numerator) [Abstract]
Income from continuing operations net of noncontrolling interest - consolidated joint ventures	$ 49,868	$ 57,959	$ 107,731	$ 140,084
Less: Preferred unit distributions	(118)	(118)	(354)	(354)
Income from continuing operations available to common unitholders	49,750	57,841	107,377	139,730
Income from discontinued operations	103,971	3,125	209,945	17,942
Net income available to common shareholders or unitholders	$ 153,721	$ 60,966	$ 317,322	$ 157,672
Weighted Average Units (Denominator) [Abstract]
Weighted Average Number of Shares or Units Outstanding, Basic	150,844	150,339	150,761	150,206
Dilutive units for long-term compensation plans	947	785	919	752
Weighted Average Number of Shares or Units Outstanding, Diluted	151,791	151,124	151,680	150,958
Liberty Property Limited Partnership [Member] | Common Units [Member]
Earnings Per Unit, Basic [Abstract]
Income from continuing operations	$ 0.33	$ 0.39	$ 0.71	$ 0.93
Income from discontinued operations	0.69	0.02	1.39	0.12
Income per common share or unit - basic	1.02	0.41	2.10	1.05
Earnings Per Unit, Diluted [Abstract]
Income from continuing operations	0.33	0.38	0.71	0.92
Income from discontinued operations	0.68	0.02	1.38	0.12
Income per common share or unit - diluted	$ 1.01	$ 0.40	$ 2.09	$ 1.04