Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
OPERATING REVENUE
Rental	$ 119,202	$ 116,193	$ 238,593	$ 230,718
Operating expense reimbursement	49,997	48,234	100,293	99,595
Total operating revenue	169,199	164,427	338,886	330,313
OPERATING EXPENSE
Rental property	31,386	28,543	61,791	60,254
Real estate taxes	20,569	19,592	41,309	39,039
General and administrative	14,619	13,255	31,823	29,203
Depreciation and amortization	40,733	38,554	82,014	77,546
Total operating expenses	107,307	99,944	216,937	206,042
Operating income	61,892	64,483	121,949	124,271
OTHER INCOME (EXPENSE)
Interest and other income	2,567	2,340	5,328	4,928
Interest expense	(30,834)	(29,358)	(60,109)	(62,200)
Total other income (expense)	(28,267)	(27,018)	(54,781)	(57,272)
Income before property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	33,625	37,465	67,168	66,999
Gain on property dispositions	335	302	858	1,463
Income taxes	(146)	(63)	(324)	(613)
Equity in earnings of unconsolidated joint ventures	769	1,109	1,685	1,643
Income from continuing operations	34,583	38,813	69,387	69,492
Discontinued operations	3,097	54,028	7,895	58,292
Net income	37,680	92,841	77,282	127,784
Noncontrolling interest – operating partnership	(3,569)	(8,120)	(6,082)	(14,355)
Noncontrolling interest - consolidated joint ventures	0	257	0	458
Preferred Stock Redemption Premium	(40)
Preferred Stock Redemption Discount			3,689
Net income available to common shareholders	34,111	84,978	71,200	113,887
Comprehensive income attributable to common shareholders
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	37,680	92,841	77,282	127,784
Other comprehensive income	(1,515)	39	801	2,183
Comprehensive Income	36,165	92,880	78,083	129,967
Less: comprehensive income attributable to noncontrolling interest	(3,522)	(8,121)	(6,108)	(14,427)
Comprehensive income attributable to common shareholders	32,643	84,759	71,975	115,540
Basic:
Income from continuing operations	$ 0.26	$ 0.28	$ 0.54	$ 0.51
Income from discontinued operations	$ 0.03	$ 0.46	$ 0.07	$ 0.49
Income per common share - basic	$ 0.29	$ 0.74	$ 0.61	$ 1.00
Diluted:
Income from continuing operations	$ 0.26	$ 0.28	$ 0.54	$ 0.50
Income from discontinued operations	$ 0.03	$ 0.46	$ 0.07	$ 0.49
Income per common share - diluted	$ 0.29	$ 0.74	$ 0.61	$ 0.99
Common Stock, Dividends, Per Share, Declared	$ 0.475	$ 0.475	$ 0.95	$ 0.95
Weighted average number of common shares outstanding
Basic	116,683	114,623	116,359	114,285
Diluted	117,559	115,406	117,165	115,087
Amounts attributable to common shareholders
Income from continuing operations	31,110	32,717	63,551	57,513
Discontinued operations	3,001	52,261	7,649	56,374
Net income available to common shareholders	34,111	84,978	71,200	113,887
Liberty Property Limited Partnership [Member]
OPERATING REVENUE
Rental	119,202	116,193	238,593	230,718
Operating expense reimbursement	49,997	48,234	100,293	99,595
Total operating revenue	169,199	164,427	338,886	330,313
OPERATING EXPENSE
Rental property	31,386	28,543	61,791	60,254
Real estate taxes	20,569	19,592	41,309	39,039
General and administrative	14,619	13,255	31,823	29,203
Depreciation and amortization	40,733	38,554	82,014	77,546
Total operating expenses	107,307	99,944	216,937	206,042
Operating income	61,892	64,483	121,949	124,271
OTHER INCOME (EXPENSE)
Interest and other income	2,567	2,340	5,328	4,928
Interest expense	(30,834)	(29,358)	(60,109)	(62,200)
Total other income (expense)	(28,267)	(27,018)	(54,781)	(57,272)
Income before property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	33,625	37,465	67,168	66,999
Gain on property dispositions	335	302	858	1,463
Income taxes	(146)	(63)	(324)	(613)
Equity in earnings of unconsolidated joint ventures	769	1,109	1,685	1,643
Income from continuing operations	34,583	38,813	69,387	69,492
Discontinued operations	3,097	54,028	7,895	58,292
Net income	37,680	92,841	77,282	127,784
Noncontrolling interest - consolidated joint ventures	0	257	0	458
Preferred unit distributions	(2,444)	(5,253)	(7,479)	(10,506)
Preferred Stock Redemption Premium	(40)
Preferred Stock Redemption Discount		0	3,689	0
Net income available to common shareholders	35,196	87,845	73,492	117,736
Comprehensive income attributable to common shareholders
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	37,680	92,841	77,282	127,784
Other comprehensive income	(1,515)	39	801	2,183
Comprehensive Income	36,165	92,880	78,083	129,967
Basic:
Income from continuing operations	$ 0.26	$ 0.28	$ 0.54	$ 0.51
Income from discontinued operations	$ 0.03	$ 0.46	$ 0.07	$ 0.49
Income per common share - basic	$ 0.29	$ 0.74	$ 0.61	$ 1.00
Diluted:
Income from continuing operations	$ 0.26	$ 0.28	$ 0.54	$ 0.50
Income from discontinued operations	$ 0.03	$ 0.46	$ 0.07	$ 0.49
Income per common share - diluted	$ 0.29	$ 0.74		$ 0.99
Common Stock, Dividends, Per Share, Declared	$ 0.475	$ 0.475	$ 0.95	$ 0.95
Weighted average number of common shares outstanding
Basic	120,450	118,549	120,147	118,212
Diluted	121,326	119,332	120,953	119,014
Net Income (Loss) Allocated to General Partners	34,111	84,978	71,200	113,887
Net Income (Loss) Allocated to Limited Partners	3,569	8,120	6,082	14,355
Amounts attributable to common shareholders
Income from continuing operations	34,583	39,070	69,387	69,950
Net income available to common shareholders	$ 35,196	$ 87,845	$ 73,492	$ 117,736