Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
OPERATING REVENUE
Rental	$ 119,578,000	$ 111,721,000	$ 238,668,000	$ 222,567,000
Operating expense reimbursement	37,202,000	33,478,000	74,354,000	67,971,000
Development service fee income	19,824,000	18,259,000	46,176,000	29,744,000
Total operating revenue	176,604,000	163,458,000	359,198,000	320,282,000
OPERATING EXPENSE
Rental property	15,029,000	13,358,000	30,318,000	28,961,000
Real estate taxes	22,605,000	20,729,000	44,958,000	41,558,000
General and administrative	11,659,000	15,203,000	30,285,000	32,196,000
Expensed pursuit costs	59,000	153,000	383,000	185,000
Systems implementation expense	1,469,000	15,000	2,175,000	15,000
Depreciation and amortization	42,708,000	41,682,000	84,781,000	83,162,000
Development service fee expense	79,808,000	17,828,000	107,875,000	28,832,000
Impairment charges - real estate assets	26,000,000	0	26,000,000	0
Total operating expenses	199,337,000	108,968,000	326,775,000	214,909,000
Operating (loss) income	(22,733,000)	54,490,000	32,423,000	105,373,000
OTHER INCOME (EXPENSE)
Interest and other income	2,663,000	1,908,000	5,142,000	3,761,000
Interest expense	(21,779,000)	(20,657,000)	(43,645,000)	(41,421,000)
Total other income (expense)	(19,116,000)	(18,749,000)	(38,503,000)	(37,660,000)
(Loss) income before gain on property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	(41,849,000)	35,741,000	(6,080,000)	67,713,000
Gain on property dispositions	48,582,000	5,895,000	52,703,000	6,702,000
Income taxes	(941,000)	(324,000)	(1,495,000)	(946,000)
Equity in earnings of unconsolidated joint ventures	7,428,000	3,990,000	14,192,000	9,721,000
Income from continuing operations	13,220,000	45,302,000	59,320,000	83,190,000
Discontinued operations (including a net loss of $0.2 million and a net gain of $89.8 million on property dispositions for the three and six months ended June 30, 2018, respectively)	7,670,000	7,516,000	105,295,000	13,872,000
Net income	20,890,000	52,818,000	164,615,000	97,062,000
Noncontrolling interest – operating partnership	(585,000)	(1,350,000)	(4,042,000)	(2,499,000)
Noncontrolling interest - consolidated joint ventures	(691,000)	(57,000)	(778,000)	(120,000)
Net income available to common shareholders or unitholders	19,614,000	51,411,000	159,795,000	94,443,000
Comprehensive income attributable to common shareholders or unitholders
Net income	20,890,000	52,818,000	164,615,000	97,062,000
Other comprehensive (loss) income - foreign currency translation	(14,138,000)	7,503,000	(6,206,000)	10,680,000
Other comprehensive income (loss) - derivative instruments	102,000	(38,000)	487,000	275,000
Other comprehensive (loss) income	(14,036,000)	7,465,000	(5,719,000)	10,955,000
Total comprehensive income	6,854,000	60,283,000	158,896,000	108,017,000
Less: comprehensive income attributable to noncontrolling interest	(949,000)	(1,582,000)	(4,687,000)	(2,875,000)
Comprehensive income attributable to common shareholders	$ 5,905,000	$ 58,701,000	$ 154,209,000	$ 105,142,000
Weighted average number of common shares or units outstanding
Basic	147,274	146,688	147,184	146,602
Diluted	148,333	147,508	148,104	147,355
Amounts attributable to common shareholders or unitholders
Income from continuing operations	$ 12,123,000	$ 44,071,000	$ 56,953,000	$ 80,896,000
Income from discontinued operations	7,491,000	7,340,000	102,842,000	13,547,000
Net income available to common shareholders or unitholders	19,614,000	51,411,000	159,795,000	94,443,000
Liberty Property Limited Partnership [Member]
OPERATING REVENUE
Rental	119,578,000	111,721,000	238,668,000	222,567,000
Operating expense reimbursement	37,202,000	33,478,000	74,354,000	67,971,000
Development service fee income	19,824,000	18,259,000	46,176,000	29,744,000
Total operating revenue	176,604,000	163,458,000	359,198,000	320,282,000
OPERATING EXPENSE
Rental property	15,029,000	13,358,000	30,318,000	28,961,000
Real estate taxes	22,605,000	20,729,000	44,958,000	41,558,000
General and administrative	11,659,000	15,203,000	30,285,000	32,196,000
Expensed pursuit costs	59,000	153,000	383,000	185,000
Systems implementation expense	1,469,000	15,000	2,175,000	15,000
Depreciation and amortization	42,708,000	41,682,000	84,781,000	83,162,000
Development service fee expense	79,808,000	17,828,000	107,875,000	28,832,000
Impairment charges - real estate assets	26,000,000	0	26,000,000	0
Total operating expenses	199,337,000	108,968,000	326,775,000	214,909,000
Operating (loss) income	(22,733,000)	54,490,000	32,423,000	105,373,000
OTHER INCOME (EXPENSE)
Interest and other income	2,663,000	1,908,000	5,142,000	3,761,000
Interest expense	(21,779,000)	(20,657,000)	(43,645,000)	(41,421,000)
Total other income (expense)	(19,116,000)	(18,749,000)	(38,503,000)	(37,660,000)
(Loss) income before gain on property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	(41,849,000)	35,741,000	(6,080,000)	67,713,000
Gain on property dispositions	48,582,000	5,895,000	52,703,000	6,702,000
Income taxes	(941,000)	(324,000)	(1,495,000)	(946,000)
Equity in earnings of unconsolidated joint ventures	7,428,000	3,990,000	14,192,000	9,721,000
Income from continuing operations	13,220,000	45,302,000	59,320,000	83,190,000
Discontinued operations (including a net loss of $0.2 million and a net gain of $89.8 million on property dispositions for the three and six months ended June 30, 2018, respectively)	7,670,000	7,516,000	105,295,000	13,872,000
Net income	20,890,000	52,818,000	164,615,000	97,062,000
Noncontrolling interest - consolidated joint ventures	(691,000)	(57,000)	(778,000)	(120,000)
Preferred unit distributions	(118,000)	(118,000)	(236,000)	(236,000)
Net income available to common shareholders or unitholders	20,081,000	52,643,000	163,601,000	96,706,000
Comprehensive income attributable to common shareholders or unitholders
Net income	20,890,000	52,818,000	164,615,000	97,062,000
Other comprehensive (loss) income - foreign currency translation	(14,138,000)	7,503,000	(6,206,000)	10,680,000
Other comprehensive income (loss) - derivative instruments	102,000	(38,000)	487,000	275,000
Other comprehensive (loss) income	(14,036,000)	7,465,000	(5,719,000)	10,955,000
Total comprehensive income	$ 6,854,000	$ 60,283,000	$ 158,896,000	$ 108,017,000
Weighted average number of common shares or units outstanding
Basic	150,794	150,216	150,704	150,130
Diluted	151,853	151,036	151,624	150,883
Net income allocated to general partners	$ 19,614,000	$ 51,411,000	$ 159,795,000	$ 94,443,000
Net income allocated to limited partners	585,000	1,350,000	4,042,000	2,499,000
Amounts attributable to common shareholders or unitholders
Income from continuing operations	12,529,000	45,245,000	58,542,000	83,070,000
Net income available to common shareholders or unitholders	$ 20,081,000	$ 52,643,000	$ 163,601,000	$ 96,706,000
Common shares [Member]
Basic:
Income from continuing operations	$ 0.08	$ 0.30	$ 0.39	$ 0.55
Income from discontinued operations	0.05	0.05	0.70	0.09
Income per common share or unit - basic	0.13	0.35	1.09	0.64
Diluted:
Income from continuing operations	0.08	0.30	0.39	0.55
Income from discontinued operations	0.05	0.05	0.69	0.09
Income per common share or unit - diluted	0.13	0.35	1.08	0.64
Distributions per common share or unit	0.40	0.40	0.80	0.80
Common Units [Member] | Liberty Property Limited Partnership [Member]
Basic:
Income from continuing operations	0.08	0.30	0.39	0.55
Income from discontinued operations	0.05	0.05	0.70	0.09
Income per common share or unit - basic	0.13	0.35	1.09	0.64
Diluted:
Income from continuing operations	0.08	0.30	0.39	0.55
Income from discontinued operations	0.05	0.05	0.69	0.09
Income per common share or unit - diluted	0.13	0.35	1.08	0.64
Distributions per common share or unit	$ 0.40	$ 0.40	$ 0.80	$ 0.80