Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
OPERATING REVENUE
Rental	$ 119,334	$ 115,760	$ 357,126	$ 345,882
Operating expense reimbursement	52,392	49,432	152,200	148,655
Total operating revenue	171,726	165,192	509,326	494,537
OPERATING EXPENSE
Rental property	34,635	31,876	95,926	91,657
Real estate taxes	20,292	19,755	61,452	58,646
General and administrative	14,621	13,617	46,444	42,819
Depreciation and amortization	40,929	38,922	122,705	116,247
Total operating expenses	110,477	104,170	326,527	309,369
Operating income	61,249	61,022	182,799	185,168
OTHER INCOME (EXPENSE)
Interest and other income	2,642	1,989	7,969	6,918
Interest expense	(30,704)	(29,173)	(89,892)	(90,198)
Total other income (expense)	(28,062)	(27,184)	(81,923)	(83,280)
Income before property dispositions, income taxes and equity in (loss) earnings of unconsolidated joint ventures	33,187	33,838	100,876	101,888
Gain on property dispositions	2,001	1,898	2,859	3,361
Income taxes	(321)	(356)	(645)	(969)
Equity in (loss) earnings of unconsolidated joint ventures	(3,082)	827	(1,397)	2,470
Income from continuing operations	31,785	36,207	101,693	106,750
Discontinued operations	(1,887)	5,474	5,487	62,715
Net income	29,898	41,681	107,180	169,465
Noncontrolling interest – operating partnership	(2,092)	(6,414)	(8,174)	(20,769)
Noncontrolling interest - consolidated joint ventures	0	53	0	511
Preferred Stock Redemption Discount			3,689
Net income available to common shareholders	27,806	35,320	99,006	149,207
Comprehensive income attributable to common shareholders
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	29,898	41,681	107,180	169,465
Other comprehensive income (loss)	2,245	(2,247)	3,047	(64)
Comprehensive Income	32,143	39,434	110,227	169,401
Less: comprehensive income attributable to noncontrolling interest	(2,161)	(6,342)	(8,269)	(20,769)
Comprehensive income attributable to common shareholders	29,982	33,092	101,958	148,632
Basic:
Income from continuing operations	$ 0.26	$ 0.26	$ 0.80	$ 0.77
(Loss) income from discontinued operations	$ (0.02)	$ 0.05	$ 0.05	$ 0.53
Income per common share - basic	$ 0.24	$ 0.31	$ 0.85	$ 1.30
Diluted:
Income from continuing operations	$ 0.26	$ 0.26	$ 0.79	$ 0.76
(Loss) income from discontinued operations	$ (0.02)	$ 0.05	$ 0.05	$ 0.53
Income per common share - diluted	$ 0.24	$ 0.31	$ 0.84	$ 1.29
Common Stock, Dividends, Per Share, Declared	$ 0.475	$ 0.475	$ 1.425	$ 1.425
Weighted average number of common shares outstanding
Basic	117,141	115,014	116,625	114,547
Diluted	118,043	115,780	117,462	115,329
Amounts attributable to common shareholders
Income from continuing operations	29,635	30,021	93,689	88,537
Discontinued operations	(1,829)	5,299	5,317	60,670
Net income available to common shareholders	27,806	35,320	99,006	149,207
Liberty Property Limited Partnership [Member]
OPERATING REVENUE
Rental	119,334	115,760	357,126	345,882
Operating expense reimbursement	52,392	49,432	152,200	148,655
Total operating revenue	171,726	165,192	509,326	494,537
OPERATING EXPENSE
Rental property	34,635	31,876	95,926	91,657
Real estate taxes	20,292	19,755	61,452	58,646
General and administrative	14,621	13,617	46,444	42,819
Depreciation and amortization	40,929	38,922	122,705	116,247
Total operating expenses	110,477	104,170	326,527	309,369
Operating income	61,249	61,022	182,799	185,168
OTHER INCOME (EXPENSE)
Interest and other income	2,642	1,989	7,969	6,918
Interest expense	(30,704)	(29,173)	(89,892)	(90,198)
Total other income (expense)	(28,062)	(27,184)	(81,923)	(83,280)
Income before property dispositions, income taxes and equity in (loss) earnings of unconsolidated joint ventures	33,187	33,838	100,876	101,888
Gain on property dispositions	2,001	1,898	2,859	3,361
Income taxes	(321)	(356)	(645)	(969)
Equity in (loss) earnings of unconsolidated joint ventures	(3,082)	827	(1,397)	2,470
Income from continuing operations	31,785	36,207	101,693	106,750
Discontinued operations	(1,887)	5,474	5,487	62,715
Net income	29,898	41,681	107,180	169,465
Noncontrolling interest - consolidated joint ventures	0	53	0	511
Preferred unit distributions	(1,211)	(5,253)	(8,690)	(15,759)
Preferred Stock Redemption Discount			3,689	0
Net income available to common shareholders	28,687	36,481	102,179	154,217
Comprehensive income attributable to common shareholders
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	29,898	41,681	107,180	169,465
Other comprehensive income (loss)	2,245	(2,247)	3,047	(64)
Comprehensive Income	32,143	39,434	110,227	169,401
Basic:
Income from continuing operations	$ 0.26	$ 0.26	$ 0.80	$ 0.77
(Loss) income from discontinued operations	$ (0.02)	$ 0.05	$ 0.05	$ 0.53
Income per common share - basic	$ 0.24	$ 0.31	$ 0.85	$ 1.30
Diluted:
Income from continuing operations	$ 0.26	$ 0.26	$ 0.79	$ 0.76
(Loss) income from discontinued operations	$ (0.02)	$ 0.05	$ 0.05	$ 0.53
Income per common share - diluted	$ 0.24	$ 0.31	$ 0.84	$ 1.29
Common Stock, Dividends, Per Share, Declared	$ 0.475	$ 0.475	$ 1.425	$ 1.425
Weighted average number of common shares outstanding
Basic	120,880	118,830	120,396	118,437
Diluted	121,782	119,596	121,233	119,219
Net Income (Loss) Allocated to General Partners	27,806	35,320	99,006	149,207
Net Income (Loss) Allocated to Limited Partners	2,092	6,414	8,174	20,769
Amounts attributable to common shareholders
Income from continuing operations	31,785	36,260	101,693	107,261
Net income available to common shareholders	$ 28,687	$ 36,481	$ 102,179	$ 154,217