Consolidated Statements of Operations (USD $) In Thousands, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
OPERATING REVENUE
Rental	$ 121,866	$ 122,383	$ 364,007	$ 363,720
Operating expense reimbursement	53,313	53,073	159,959	157,539
Total operating revenue	175,179	175,456	523,966	521,259
OPERATING EXPENSE
Rental property	35,563	34,790	102,013	102,653
Real estate taxes	21,039	21,306	62,528	63,253
General and administrative	13,625	12,608	42,848	40,023
Depreciation and amortization	41,414	39,996	123,840	119,091
Total operating expenses	111,641	108,700	331,229	325,020
Operating income	63,538	66,756	192,737	196,239
OTHER INCOME (EXPENSE)
Interest and other income	2,019	2,400	7,011	7,748
Interest expense	(31,188)	(32,410)	(96,354)	(103,922)
Total other income (expense)	(29,169)	(30,010)	(89,343)	(96,174)
Income before property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	34,369	36,746	103,394	100,065
Gain on property dispositions	1,898	691	3,361	3,701
Income taxes	(356)	(475)	(969)	(1,430)
Equity in earnings of unconsolidated joint ventures	827	385	2,470	1,562
Income from continuing operations	36,738	37,347	108,256	103,898
Discontinued operations	4,943	3,659	61,209	12,944
Net income	41,681	41,006	169,465	116,842
Noncontrolling interest - operating partnership	(6,414)	(6,451)	(20,769)	(19,155)
Noncontrolling interest - consolidated joint ventures	53	89	511	(47)
Net income available to common shareholders	35,320	34,644	149,207	97,640
Basic:
Income from continuing operations	$ 0.27	$ 0.28	$ 0.78	$ 0.76
Income from discontinued operations	$ 0.04	$ 0.03	$ 0.52	$ 0.11
Income per common share - basic	$ 0.31	$ 0.31	$ 1.30	$ 0.87
Diluted:
Income from continuing operations	$ 0.27	$ 0.27	$ 0.78	$ 0.75
Income from discontinued operations	$ 0.04	$ 0.03	$ 0.51	$ 0.11
Income per common share - diluted	$ 0.31	$ 0.30	$ 1.29	$ 0.86
Distributions per common share	$ 0.475	$ 0.475	$ 1.425	$ 1.425
Weighted average number of common shares outstanding
Basic	115,014	113,077	114,547	112,708
Diluted	115,780	113,773	115,329	113,388
Amounts attributable to common shareholders
Income from continuing operations	30,535	31,108	89,993	85,131
Discontinued operations	4,785	3,536	59,214	12,509
Net income available to common shareholders	35,320	34,644	149,207	97,640
Liberty Property Limited Partnership [Member]
OPERATING REVENUE
Rental	121,866	122,383	364,007	363,720
Operating expense reimbursement	53,313	53,073	159,959	157,539
Total operating revenue	175,179	175,456	523,966	521,259
OPERATING EXPENSE
Rental property	35,563	34,790	102,013	102,653
Real estate taxes	21,039	21,306	62,528	63,253
General and administrative	13,625	12,608	42,848	40,023
Depreciation and amortization	41,414	39,996	123,840	119,091
Total operating expenses	111,641	108,700	331,229	325,020
Operating income	63,538	66,756	192,737	196,239
OTHER INCOME (EXPENSE)
Interest and other income	2,019	2,400	7,011	7,748
Interest expense	(31,188)	(32,410)	(96,354)	(103,922)
Total other income (expense)	(29,169)	(30,010)	(89,343)	(96,174)
Income before property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	34,369	36,746	103,394	100,065
Gain on property dispositions	1,898	691	3,361	3,701
Income taxes	(356)	(475)	(969)	(1,430)
Equity in earnings of unconsolidated joint ventures	827	385	2,470	1,562
Income from continuing operations	36,738	37,347	108,256	103,898
Discontinued operations	4,943	3,659	61,209	12,944
Net income	41,681	41,006	169,465	116,842
Noncontrolling interest - consolidated joint ventures	53	89	511	(47)
Preferred unit distributions	(5,253)	(5,253)	(15,759)	(15,759)
Net income available to common shareholders	36,481	35,842	154,217	101,036
Basic:
Income from continuing operations	$ 0.27	$ 0.28	$ 0.78	$ 0.76
Income from discontinued operations	$ 0.04	$ 0.03	$ 0.52	$ 0.11
Income per common share - basic	$ 0.31	$ 0.31	$ 1.30	$ 0.87
Diluted:
Income from continuing operations	$ 0.27	$ 0.27	$ 0.78	$ 0.75
Income from discontinued operations	$ 0.04	$ 0.03	$ 0.51	$ 0.11
Income per common share - diluted	$ 0.31	$ 0.30	$ 1.29	$ 0.86
Distributions per common share	$ 0.475	$ 0.475	$ 1.425	$ 1.425
Weighted average number of common shares outstanding
Basic	118,830	117,020	118,437	116,657
Diluted	119,596	117,716	119,219	117,337
Net Income (Loss) Allocated to General Partners	35,320	34,644	149,207	97,640
Net Income (Loss) Allocated to Limited Partners	6,414	6,451	20,769	19,155
Amounts attributable to common shareholders
Income from continuing operations	36,791	37,436	108,767	103,851
Net income available to common shareholders	$ 36,481	$ 35,842	$ 154,217	$ 101,036