Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
OPERATING REVENUE
Rental	$ 119,591	$ 114,724
Operating expense reimbursement	50,346	51,410
Total operating revenue	169,937	166,134
OPERATING EXPENSE
Rental property	30,440	31,750
Real estate taxes	20,782	19,489
General and administrative	17,204	15,949
Depreciation and amortization	41,367	39,077
Total operating expenses	109,793	106,265
Operating income	60,144	59,869
OTHER INCOME (EXPENSE)
Interest and other income	2,762	2,589
Interest expense	(28,476)	(32,889)
Total other income (expense)	(25,714)	(30,300)
Income before property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	34,430	29,569
Gain on property dispositions	523	1,161
Income taxes	(178)	(550)
Equity in earnings of unconsolidated joint ventures	916	534
Income from continuing operations	35,691	30,714
Discontinued operations	3,911	4,229
Net income	39,602	34,943
Noncontrolling interest – operating partnership	(2,513)	(6,235)
Noncontrolling interest - consolidated joint ventures	0	201
Preferred Stock Redemption Discount	3,729
Net income available to common shareholders	37,089	28,909
Comprehensive Income (Loss), Net of Tax, Attributable to Common Shareholders [Abstract]
Other comprehensive income	2,317	2,144
Comprehensive Income	41,919	37,087
Less: comprehensive income attributable to noncontrolling interest	(2,586)	(6,306)
Comprehensive income attributable to common shareholders	39,333	30,781
Basic:
Income from continuing operations	$ 0.29	$ 0.21
Income from discontinued operations	$ 0.03	$ 0.04
Income per common share - basic	$ 0.32	$ 0.25
Diluted:
Income from continuing operations	$ 0.29	$ 0.21
Income from discontinued operations	$ 0.03	$ 0.04
Income per common share - diluted	$ 0.32	$ 0.25
Common Stock, Dividends, Per Share, Declared	$ 0.475	$ 0.475
Weighted average number of common shares outstanding
Basic	115,972	114,013
Diluted	116,743	114,766
Amounts attributable to common shareholders
Income from continuing operations	33,301	24,820
Discontinued operations	3,788	4,089
Net income available to common shareholders	37,089	28,909
Liberty Property Limited Partnership [Member]
OPERATING REVENUE
Rental	119,591	114,724
Operating expense reimbursement	50,346	51,410
Total operating revenue	169,937	166,134
OPERATING EXPENSE
Rental property	30,440	31,750
Real estate taxes	20,782	19,489
General and administrative	17,204	15,949
Depreciation and amortization	41,367	39,077
Total operating expenses	109,793	106,265
Operating income	60,144	59,869
OTHER INCOME (EXPENSE)
Interest and other income	2,762	2,589
Interest expense	(28,476)	(32,889)
Total other income (expense)	(25,714)	(30,300)
Income before property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	34,430	29,569
Gain on property dispositions	523	1,161
Income taxes	(178)	(550)
Equity in earnings of unconsolidated joint ventures	916	534
Income from continuing operations	35,691	30,714
Discontinued operations	3,911	4,229
Net income	39,602	34,943
Noncontrolling interest - consolidated joint ventures	0	201
Preferred unit distributions	(5,035)	(5,253)
Preferred Stock Redemption Discount	3,729	0
Net income available to common shareholders	38,296	29,891
Comprehensive Income (Loss), Net of Tax, Attributable to Common Shareholders [Abstract]
Other comprehensive income	2,317	2,144
Comprehensive Income	41,919	37,087
Basic:
Income from continuing operations	$ 0.29	$ 0.21
Income from discontinued operations	$ 0.03	$ 0.04
Income per common share - basic	$ 0.32	$ 0.25
Diluted:
Income from continuing operations	$ 0.29	$ 0.21
Income from discontinued operations	$ 0.03	$ 0.04
Income per common share - diluted	$ 0.32	$ 0.25
Common Stock, Dividends, Per Share, Declared	$ 0.475	$ 0.475
Weighted average number of common shares outstanding
Basic	119,781	117,942
Diluted	120,552	118,695
Net Income (Loss) Allocated to General Partners	37,089	28,909
Net Income (Loss) Allocated to Limited Partners	2,513	6,235
Amounts attributable to common shareholders
Income from continuing operations	35,691	30,915
Net income available to common shareholders	$ 38,296	$ 29,891