Income per Common Unit of the Operating Partnership Income per Common Unit of the Operating Partnership, Diluted (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Income from continuing operations net of noncontrolling interest	$ 34,290	$ 22,316	$ 88,430	$ 72,048
Discontinued operations	136	6,544	48,276	70,008
Net income available to common shareholders	34,423	28,699	135,572	140,047
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Weighted Average Number of Shares Outstanding, Basic	147,422	135,628	146,987	124,889
Dilutive units for long-term compensation plans	666	700	674	766
Weighted Average Number of Shares Outstanding, Diluted	148,088	136,328	147,661	125,655
Liberty Property Limited Partnership [Member]
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Income from continuing operations net of noncontrolling interest	35,231	22,998	90,914	77,433
Less: Preferred unit distributions	(118)	(118)	(354)	(2,001)
Excess of preferred unit redemption over carrying amount			0	(1,236)
Income from Continuing Operations available to Common Unitholders	35,113	22,880	90,560	74,196
Discontinued operations	136	6,544	48,276	70,008
Net income available to common shareholders	$ 35,249	$ 29,424	$ 138,836	$ 144,204
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Weighted Average Number of Shares Outstanding, Basic	150,976	139,320	150,541	128,595
Dilutive units for long-term compensation plans	666	700	674	766
Weighted Average Number of Shares Outstanding, Diluted	151,642	140,020	151,215	129,361
Liberty Property Limited Partnership [Member] | Common Units [Member]
Earnings Per Share, Basic [Abstract]
Income from Continuing Operations, Per Basic Share	$ 0.23	$ 0.16	$ 0.60	$ 0.58
Income from Discontinued Operations, Per Basic Share	$ 0.00	$ 0.05	$ 0.32	$ 0.54
Income per common share - basic	$ 0.23	$ 0.21	$ 0.92	$ 1.12
Earnings Per Share, Diluted [Abstract]
Income from Continuing Operations, Per Diluted Share	$ 0.23	$ 0.16	$ 0.60	$ 0.57
Income from Discontinued Operations, Per Diluted Share	$ 0.00	$ 0.05	$ 0.32	$ 0.54
Income per common share - diluted	$ 0.23	$ 0.21	$ 0.92	$ 1.11