Consolidated Statements of Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
OPERATING REVENUE
Rental	$ 123,912	$ 117,369
Operating expense reimbursement	52,661	49,573
Total operating revenue	176,573	166,942
OPERATING EXPENSE
Rental property	31,916	30,018
Real estate taxes	21,552	20,311
General and administrative	19,833	17,201
Depreciation and amortization	44,973	40,725
Total operating expenses	118,274	108,255
Operating income	58,299	58,687
OTHER INCOME (EXPENSE)
Interest and other income	2,632	2,460
Interest expense	(31,934)	(28,193)
Total other income (expense)	(29,302)	(25,733)
Income before gain on property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	28,997	32,954
Gain on property dispositions	1,800	523
Income taxes	(491)	(178)
Equity in earnings of unconsolidated joint ventures	1,757	916
Income from continuing operations	32,063	34,215
Discontinued operations (including net gains on property dispositions of $41,713 and $1,064 for the quarters ended March 31, 2013 and 2012, respectively)	42,593	5,387
Net income	74,656	39,602
Noncontrolling interest – operating partnership	(3,417)	(2,513)
Noncontrolling interest - consolidated joint ventures	0	0
Net income available to common shareholders	71,239	37,089
Comprehensive income attributable to common shareholders
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	74,656	39,602
Other comprehensive (loss) income	(4,851)	2,317
Total Comprehensive Income	69,805	41,919
Less: comprehensive income attributable to noncontrolling interest	(3,271)	(2,586)
Comprehensive income attributable to common shareholders	66,534	39,333
Basic:
Income from continuing operations	$ 0.25	$ 0.28
Income from discontinued operations	$ 0.35	$ 0.04
Income per common share - basic	$ 0.60	$ 0.32
Diluted:
Income from continuing operations	$ 0.25	$ 0.28
Income from discontinued operations	$ 0.35	$ 0.04
Income per common share - diluted	$ 0.60	$ 0.32
Common Stock, Dividends, Per Share, Declared	$ 0.475	$ 0.475
Weighted average number of common shares outstanding
Basic	118,688	115,972
Diluted	119,532	116,743
Amounts attributable to common shareholders
Income from continuing operations	29,925	31,872
Discontinued operations	41,314	5,217
Net income available to common shareholders	71,239	37,089
Liberty Property Limited Partnership [Member]
OPERATING REVENUE
Rental	123,912	117,369
Operating expense reimbursement	52,661	49,573
Total operating revenue	176,573	166,942
OPERATING EXPENSE
Rental property	31,916	30,018
Real estate taxes	21,552	20,311
General and administrative	19,833	17,201
Depreciation and amortization	44,973	40,725
Total operating expenses	118,274	108,255
Operating income	58,299	58,687
OTHER INCOME (EXPENSE)
Interest and other income	2,632	2,460
Interest expense	(31,934)	(28,193)
Total other income (expense)	(29,302)	(25,733)
Income before gain on property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	28,997	32,954
Gain on property dispositions	1,800	523
Income taxes	(491)	(178)
Equity in earnings of unconsolidated joint ventures	1,757	916
Income from continuing operations	32,063	34,215
Discontinued operations (including net gains on property dispositions of $41,713 and $1,064 for the quarters ended March 31, 2013 and 2012, respectively)	42,593	5,387
Net income	74,656	39,602
Noncontrolling interest - consolidated joint ventures	0	0
Preferred unit distributions	(1,211)	(5,035)
Net income available to common shareholders	73,445	38,296
Comprehensive income attributable to common shareholders
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	74,656	39,602
Other comprehensive (loss) income	(4,851)	2,317
Total Comprehensive Income	69,805	41,919
Basic:
Income from continuing operations	$ 0.25	$ 0.28
Income from discontinued operations	$ 0.35	$ 0.04
Income per common share - basic	$ 0.60	$ 0.32
Diluted:
Income from continuing operations	$ 0.25	$ 0.28
Income from discontinued operations	$ 0.35	$ 0.04
Income per common share - diluted	$ 0.60	$ 0.32
Common Stock, Dividends, Per Share, Declared	$ 0.475	$ 0.475
Weighted average number of common shares outstanding
Basic	122,402	119,781
Diluted	123,246	120,552
Net Income Allocated to General Partners	71,239	37,089
Net Income Allocated to Limited Partners	3,417	2,513
Amounts attributable to common shareholders
Income from continuing operations	32,063	34,215
Net income available to common shareholders	73,445	38,296
Preferred Stock Redemption Discount	$ 0	$ 3,729