Consolidated Statements of Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
OPERATING REVENUE
Rental	$ 124,883	$ 116,068	$ 247,658	$ 232,289
Operating expense reimbursement	53,221	48,426	105,134	97,169
Total operating revenue	178,104	164,494	352,792	329,458
OPERATING EXPENSE
Rental property	32,985	30,369	64,533	59,906
Real estate taxes	21,776	19,740	42,900	39,651
General and administrative	16,491	14,589	36,321	31,781
Depreciation and amortization	44,907	39,821	89,524	80,187
Total operating expenses	116,159	104,519	233,278	211,525
Operating income	61,945	59,975	119,514	117,933
OTHER INCOME (EXPENSE)
Interest and other income	2,371	2,265	4,993	4,715
Interest expense	(32,003)	(30,328)	(63,729)	(58,334)
Total other income (expense)	(29,632)	(28,063)	(58,736)	(53,619)
Income before gain on property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	32,313	31,912	60,778	64,314
Gain on property dispositions	3,071	335	4,871	858
Income taxes	(660)	(146)	(1,151)	(324)
Equity in earnings of unconsolidated joint ventures	1,566	769	3,323	1,685
Income from continuing operations	36,290	32,870	67,821	66,533
Discontinued operations (including net gain on property dispositions of $7,625 and $2,981 for the three months ended June 30, 2013 and 2012, respectively)	6,953	4,810	50,078	10,749
Net income	43,243	37,680	117,899	77,282
Noncontrolling interest – operating partnership	(3,134)	(3,569)	(6,551)	(6,082)
Preferred stock redemption premium	(1,236)		(1,236)
Net income available to common shareholders	40,109	34,111	111,348	71,200
Comprehensive income attributable to common shareholders
Net income	43,243	37,680	117,899	77,282
Other comprehensive income (loss)	40	(1,515)	(4,812)	802
Total comprehensive income	43,283	36,165	113,087	78,084
Less: comprehensive income attributable to noncontrolling interest	(3,135)	(3,522)	(6,406)	(6,108)
Comprehensive income attributable to common shareholders	40,148	32,643	106,681	71,976
Basic:
Income from continuing operations	$ 0.27	$ 0.25	$ 0.53	$ 0.52
Income from discontinued operations	$ 0.06	$ 0.04	$ 0.40	$ 0.09
Income per common share - basic	$ 0.33	$ 0.29	$ 0.93	$ 0.61
Diluted:
Income from continuing operations	$ 0.27	$ 0.25	$ 0.53	$ 0.52
Income from discontinued operations	$ 0.06	$ 0.04	$ 0.40	$ 0.09
Income per common share - diluted	$ 0.33	$ 0.29	$ 0.93	$ 0.61
Distributions per common share or unit	$ 0.475	$ 0.475	$ 0.95	$ 0.95
Weighted average number of common shares outstanding
Basic	120,081	116,683	119,416	116,359
Diluted	120,911	117,559	120,229	117,165
Amounts attributable to common shareholders
Income from continuing operations	33,362	29,449	62,762	60,786
Discontinued operations	6,747	4,662	48,586	10,414
Net income available to common shareholders	40,109	34,111	111,348	71,200
Liberty Property Limited Partnership [Member]
OPERATING REVENUE
Rental	124,883	116,068	247,658	232,289
Operating expense reimbursement	53,221	48,426	105,134	97,169
Total operating revenue	178,104	164,494	352,792	329,458
OPERATING EXPENSE
Rental property	32,985	30,369	64,533	59,906
Real estate taxes	21,776	19,740	42,900	39,651
General and administrative	16,491	14,589	36,321	31,781
Depreciation and amortization	44,907	39,821	89,524	80,187
Total operating expenses	116,159	104,519	233,278	211,525
Operating income	61,945	59,975	119,514	117,933
OTHER INCOME (EXPENSE)
Interest and other income	2,371	2,265	4,993	4,715
Interest expense	(32,003)	(30,328)	(63,729)	(58,334)
Total other income (expense)	(29,632)	(28,063)	(58,736)	(53,619)
Income before gain on property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	32,313	31,912	60,778	64,314
Gain on property dispositions	3,071	335	4,871	858
Income taxes	(660)	(146)	(1,151)	(324)
Equity in earnings of unconsolidated joint ventures	1,566	769	3,323	1,685
Income from continuing operations	36,290	32,870	67,821	66,533
Discontinued operations (including net gain on property dispositions of $7,625 and $2,981 for the three months ended June 30, 2013 and 2012, respectively)	6,953	4,810	50,078	10,749
Net income	43,243	37,680	117,899	77,282
Preferred unit distributions	(672)	(2,444)	(1,883)	(7,479)
Preferred stock redemption premium	(1,236)	(40)	(1,236)
Preferred stock redemption discount				3,689
Net income available to common shareholders	41,335	35,196	114,780	73,492
Comprehensive income attributable to common shareholders
Net income	43,243	37,680	117,899	77,282
Other comprehensive income (loss)	40	(1,515)	(4,812)	801
Total comprehensive income	43,283	36,165	113,087	78,083
Basic:
Income from continuing operations	$ 0.27	$ 0.25	$ 0.53	$ 0.52
Income from discontinued operations	$ 0.06	$ 0.04	$ 0.40	$ 0.09
Income per common share - basic	$ 0.33	$ 0.29	$ 0.93	$ 0.61
Diluted:
Income from continuing operations	$ 0.27	$ 0.25	$ 0.53	$ 0.52
Income from discontinued operations	$ 0.06	$ 0.04	$ 0.40	$ 0.09
Income per common share - diluted	$ 0.33	$ 0.29	$ 0.93	$ 0.61
Distributions per common share or unit	$ 0.475	$ 0.475	$ 0.95	$ 0.95
Weighted average number of common shares outstanding
Basic	123,795	120,450	123,130	120,147
Diluted	124,625	121,326	123,943	120,953
Net income allocated to general partners	40,109	34,111	111,348	71,200
Net income allocated to limited partners	3,134	3,569	6,551	6,082
Amounts attributable to common shareholders
Income from continuing operations	36,290	32,870	67,821	66,533
Net income available to common shareholders	$ 41,335	$ 35,196	$ 114,780	$ 73,492