Liberty Property Trust (LPT) 10-Q 1 May 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document	3 Months Ended
	Mar. 31, 2014	Apr. 28, 2014
Entity Information [Line Items]	'	'
Entity Registrant Name	'LIBERTY PROPERTY TRUST	'
Entity Central Index Key	'0000921112	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Document Type	'10-Q	'
Document Period End Date	31-Mar-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'
Amendment Flag	'false	'
Entity Common Stock, Shares Outstanding	'	147,695,735
Liberty Property Limited Partnership [Member]	'	'
Entity Information [Line Items]	'	'
Entity Registrant Name	'LIBERTY PROPERTY LIMITED PARTNERSHIP	'
Entity Central Index Key	'0000921113	'

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2014	Dec. 31, 2013
ASSETS	'	'
Land and land improvements	$1,149,233,000	$1,139,455,000
Building and improvements	5,206,349,000	5,144,758,000
Less accumulated depreciation	-1,094,397,000	-1,057,680,000
Operating real estate	5,261,185,000	5,226,533,000
Development in progress	242,771,000	209,187,000
Land held for development	239,755,000	233,055,000
Net real estate	5,743,711,000	5,668,775,000
Cash and cash equivalents	370,553,000	163,414,000
Restricted cash	20,041,000	51,456,000
Accounts receivable	17,963,000	13,900,000
Deferred rent receivable	102,729,000	99,956,000
Deferred financing and leasing costs, net of accumulated amortization (2014, $150,476; 2013, $140,958)	222,832,000	226,607,000
Investments in and advances to unconsolidated joint ventures	181,249,000	179,655,000
Assets held for sale	0	275,957,000
Prepaid expenses and other assets	103,586,000	95,840,000
Total assets	6,762,664,000	6,775,560,000
LIABILITIES	'	'
Mortgage loans	542,809,000	545,306,000
Unsecured notes	2,708,440,000	2,708,213,000
Credit facility	0	0
Accounts payable	53,458,000	70,406,000
Accrued interest	42,218,000	25,777,000
Dividend and distributions payable	71,653,000	71,323,000
Other liabilities	215,253,000	250,819,000
Total liabilities	3,633,831,000	3,671,844,000
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of March 31, 2014 and December 31, 2013	7,537,000	7,537,000
EQUITY	'	'
Common shares of beneficial interest, $.001 par value, 183,987,000 shares authorized; 148,541,749 (includes 1,249,909 in treasury) and 147,846,801 (includes 1,249,909 in treasury) shares issued and outstanding as of March 31, 2014 and December 31, 2013, respectively	149,000	148,000
Additional paid-in capital	3,691,717,000	3,669,618,000
Accumulated other comprehensive loss	10,557,000	9,742,000
Distributions in excess of net income	-589,775,000	-591,713,000
Common shares in treasury, at cost, 1,249,909 shares as of March 31, 2014 and December 31, 2013	-51,951,000	-51,951,000
Total Liberty Property Trust shareholders' equity	3,060,697,000	3,035,844,000
Noncontrolling interest - operating partnership	'	'
Noncontrolling interest - consolidated joint ventures	3,918,000	3,622,000
Total equity	3,121,296,000	3,096,179,000
Total liabilities, noncontrolling interest - operating partnership and equity	6,762,664,000	6,775,560,000
Limited partners’ equity – 3,553,566 and 3,556,556 common units outstanding as of March 31, 2014 and December 31, 2013, respectively	'	'
Noncontrolling interest - operating partnership	'	'
Noncontrolling interest - operating partnerships	56,681,000	56,713,000
Liberty Property Limited Partnership [Member]	'	'
ASSETS	'	'
Land and land improvements	1,149,233,000	1,139,455,000
Building and improvements	5,206,349,000	5,144,758,000
Less accumulated depreciation	-1,094,397,000	-1,057,680,000
Operating real estate	5,261,185,000	5,226,533,000
Development in progress	242,771,000	209,187,000
Land held for development	239,755,000	233,055,000
Net real estate	5,743,711,000	5,668,775,000
Cash and cash equivalents	370,553,000	163,414,000
Restricted cash	20,041,000	51,456,000
Accounts receivable	17,963,000	13,900,000
Deferred rent receivable	102,729,000	99,956,000
Deferred financing and leasing costs, net of accumulated amortization (2014, $150,476; 2013, $140,958)	222,832,000	226,607,000
Investments in and advances to unconsolidated joint ventures	181,249,000	179,655,000
Assets held for sale	0	275,957,000
Prepaid expenses and other assets	103,586,000	95,840,000
Total assets	6,762,664,000	6,775,560,000
LIABILITIES	'	'
Mortgage loans	542,809,000	545,306,000
Unsecured notes	2,708,440,000	2,708,213,000
Credit facility	0	0
Accounts payable	53,458,000	70,406,000
Accrued interest	42,218,000	25,777,000
Dividend and distributions payable	71,653,000	71,323,000
Other liabilities	215,253,000	250,819,000
Total liabilities	3,633,831,000	3,671,844,000
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of March 31, 2014 and December 31, 2013	7,537,000	7,537,000
EQUITY	'	'
General partner’s equity - 147,291,840 (net of 1,249,909 treasury units) and 146,596,892 (net of 1,249,909 treasury units) common units outstanding as of March 31, 2014 and December 31, 2013, respectively	3,060,697,000	3,035,844,000
Noncontrolling interest - operating partnership	'	'
Noncontrolling interest - consolidated joint ventures	3,918,000	3,622,000
Total equity	3,121,296,000	3,096,179,000
Total liabilities, noncontrolling interest - operating partnership and equity	6,762,664,000	6,775,560,000
Liberty Property Limited Partnership [Member] | Limited partners’ equity – 3,553,566 and 3,556,556 common units outstanding as of March 31, 2014 and December 31, 2013, respectively	'	'
EQUITY	'	'
Limited partners' equity	$56,681,000	$56,713,000

Balance_Sheet_Parenthetical_Pa

Balance Sheet Parenthetical (Parentheticals) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Amortized Cost on Deferred Financing and Leasing Costs	$150,476,000	$140,958,000
Noncontrolling Interest Operating Partnership Common Units Outstanding	3,553,566	3,556,556
Preferred Units, Outstanding	0	0
Common Stock, Par or Stated Value Per Share	$0.00	$0.00
Common Stock, Shares Authorized	183,987,000	183,987,000
Common Stock, Shares, Issued	148,541,749	147,846,801
Common Stock, Shares, Outstanding	148,541,749	147,846,801
Treasury Stock, Shares	1,249,909	1,249,909
Liberty Property Limited Partnership [Member]	'	'
Amortized Cost on Deferred Financing and Leasing Costs	$150,476,000	$140,958,000
Limited Partners' Capital Account, Units Outstanding	3,553,566	3,556,556
Preferred Units, Outstanding	0	0
Common Stock, Shares, Outstanding	147,291,840	146,596,892
Treasury Stock, Shares	1,249,909	1,249,909
Series I 2 [Member]	'	'
Preferred Units, Outstanding	301,483	301,483
Series I 2 [Member] | Liberty Property Limited Partnership [Member]	'	'
Preferred Units, Outstanding	301,483	301,483

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
OPERATING REVENUE	'	'
Rental	$138,934	$104,716
Operating expense reimbursement	58,681	42,411
Total operating revenue	197,615	147,127
OPERATING EXPENSE	'	'
Rental property	38,561	25,229
Real estate taxes	24,501	17,957
General and administrative	18,361	19,793
Depreciation and amortization	56,734	37,220
Total operating expenses	138,157	100,199
Operating income	59,458	46,928
OTHER INCOME (EXPENSE)	'	'
Other income	2,452	4,373
Interest expense	-39,207	-27,739
Total other income (expense)	-36,755	-23,366
Income before income taxes and equity in earnings of unconsolidated joint ventures	22,703	23,562
Income taxes	-531	-491
Equity in earnings of unconsolidated joint ventures	4,159	1,757
Income from continuing operations	26,331	24,828
Discontinued operations (including net gain on property dispositions of $46,117 and $41,713 for the three months ended March 31, 2014 and 2013, respectively)	47,775	49,828
Net income	74,106	74,656
Noncontrolling interest – operating partnership	-1,853	-3,417
Noncontrolling interest - consolidated joint ventures	-353	0
Net income available to common shareholders	71,900	71,239
Comprehensive income attributable to common shareholders	'	'
Net income	74,106	74,656
Other comprehensive income (loss) - foreign currency translation	1,346	-4,851
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	-511	0
Other Comprehensive Income (Loss), Net of Tax	835	-4,851
Total comprehensive income	74,941	69,805
Less: comprehensive income attributable to noncontrolling interest	-2,226	-3,271
Comprehensive income attributable to common shareholders	72,715	66,534
Basic:	'	'
Income from continuing operations	$0.17	$0.19
Income from discontinued operations	$0.32	$0.41
Income per common share - basic	$0.49	$0.60
Diluted:	'	'
Income from continuing operations	$0.17	$0.19
Income from discontinued operations	$0.32	$0.41
Income per common share - diluted	$0.49	$0.60
Distributions per common share or unit	$0.48	$0.48
Weighted average number of common shares outstanding	'	'
Basic	146,425	118,688
Diluted	147,095	119,532
Amounts attributable to common shareholders	'	'
Income from continuing operations	25,250	22,908
Discontinued operations	46,650	48,331
Net income available to common shareholders	71,900	71,239
Liberty Property Limited Partnership [Member]	'	'
OPERATING REVENUE	'	'
Rental	138,934	104,716
Operating expense reimbursement	58,681	42,411
Total operating revenue	197,615	147,127
OPERATING EXPENSE	'	'
Rental property	38,561	25,229
Real estate taxes	24,501	17,957
General and administrative	18,361	19,793
Depreciation and amortization	56,734	37,220
Total operating expenses	138,157	100,199
Operating income	59,458	46,928
OTHER INCOME (EXPENSE)	'	'
Other income	2,452	4,373
Interest expense	-39,207	-27,739
Total other income (expense)	-36,755	-23,366
Income before income taxes and equity in earnings of unconsolidated joint ventures	22,703	23,562
Income taxes	-531	-491
Equity in earnings of unconsolidated joint ventures	4,159	1,757
Income from continuing operations	26,331	24,828
Discontinued operations (including net gain on property dispositions of $46,117 and $41,713 for the three months ended March 31, 2014 and 2013, respectively)	47,775	49,828
Net income	74,106	74,656
Noncontrolling interest - consolidated joint ventures	-353	0
Preferred unit distributions	-118	-1,211
Net income available to common shareholders	73,635	73,445
Comprehensive income attributable to common shareholders	'	'
Net income	74,106	74,656
Other comprehensive income (loss) - foreign currency translation	1,346	-4,851
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	-511	0
Other Comprehensive Income (Loss), Net of Tax	835	-4,851
Total comprehensive income	74,941	69,805
Basic:	'	'
Income from continuing operations	$0.17	$0.19
Income from discontinued operations	$0.32	$0.41
Income per common share - basic	$0.49	$0.60
Diluted:	'	'
Income from continuing operations	$0.17	$0.19
Income from discontinued operations	$0.32	$0.41
Income per common share - diluted	$0.49	$0.60
Distributions per common share or unit	$0.48	$0.48
Weighted average number of common shares outstanding	'	'
Basic	149,981	122,402
Diluted	150,651	123,246
Net income allocated to general partners	71,900	71,239
Net income allocated to limited partners	1,853	3,417
Amounts attributable to common shareholders	'	'
Income from continuing operations	25,978	24,828
Net income available to common shareholders	$73,635	$73,445

Income_Statement_Parenthetical

Income Statement Parenthetical (Parentheticals) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Gain on property dispositions	$46,117	$41,713
Liberty Property Limited Partnership [Member]	'	'
Gain on property dispositions	$46,117	$41,713

Consolidated_Statement_of_Equi

Consolidated Statement of Equity (USD $)	Total	Common Shares Of Beneficial Interest [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income [Member]	Distributions in Excess of Net Income [Member]	Common Shares Held in Treasury [Member]	Total Liberty Property Trust Shareholders' Equity [Member]	Noncontrolling interest operating partnership-Common [Member]	Noncontrolling interest operating partnership-Preferred [Member]	Noncontrolling interest-consolidated joint ventures [Member]	Liberty Property Limited Partnership [Member]	Liberty Property Limited Partnership [Member]	Liberty Property Limited Partnership [Member]	Liberty Property Limited Partnership [Member]	Liberty Property Limited Partnership [Member]
												General Partners Equity [Member]	Noncontrolling interest operating partnership-Common [Member]	Noncontrolling interest operating partnership-Preferred [Member]	Noncontrolling interest-consolidated joint ventures [Member]
Beginning Balance at Dec. 31, 2013	$3,096,179,000	$148,000	$3,669,618,000	$9,742,000	($591,713,000)	($51,951,000)	$3,035,844,000	$56,713,000	$0	$3,622,000	$3,096,179,000	$3,035,844,000	$56,713,000	$0	$3,622,000
Net proceeds from the issuance of common shares	15,472,000	1,000	15,471,000	'	'	'	15,472,000	'	'	'	'	'	'	'	'
Net income	74,106,000	'	'	'	71,900,000	'	71,900,000	1,735,000	118,000	353,000	74,106,000	71,900,000	1,735,000	118,000	353,000
Redemption of limited partners common units for common shares	'	'	'	'	'	'	'	'	'	'	0	48,000	-48,000	'	'
Contributions from partners	'	'	'	'	'	'	'	'	'	'	22,052,000	22,052,000	'	'	'
Distributions	-71,876,000	'	'	'	-69,962,000	'	-69,962,000	-1,739,000	-118,000	-57,000	'	'	'	'	'
Distributions to partners	'	'	'	'	'	'	'	'	'	'	-71,876,000	-69,962,000	-1,739,000	-118,000	-57,000
Share-based compensation	6,580,000	'	6,580,000	'	'	'	6,580,000	'	'	'	'	'	'	'	'
Foreign currency translation adjustment	1,346,000	'	'	1,314,000	'	'	1,314,000	32,000	'	'	1,346,000	1,314,000	32,000	'	'
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	-511,000	'	0	-499,000	0	0	-499,000	-12,000	0	0	-511,000	-499,000	-12,000	'	'
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests, Common Units	0	'	48,000	'	'	'	48,000	-48,000	'	'	'	'	'	'	'
Ending Balance at Mar. 31, 2014	$3,121,296,000	$149,000	$3,691,717,000	$10,557,000	($589,775,000)	($51,951,000)	$3,060,697,000	$56,681,000	$0	$3,918,000	$3,121,296,000	$3,060,697,000	$56,681,000	$0	$3,918,000

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
OPERATING ACTIVITIES	'	'
Net income	$74,106	$74,656
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	57,589	45,585
Amortization of deferred financing costs	1,510	980
Equity in earnings of unconsolidated joint ventures	-4,159	-1,757
Distributions from unconsolidated joint ventures	0	265
Gain on property dispositions	-46,117	-41,713
Share-based compensation	6,580	4,445
Other	-635	-1,612
Changes in operating assets and liabilities:	'	'
Restricted cash	31,726	4,639
Accounts receivable	-4,052	642
Deferred rent receivable	-2,765	-3,246
Prepaid expenses and other assets	-26,557	1,319
Accounts payable	6,562	1,136
Accrued interest	16,441	18,867
Other liabilities	-36,537	-12,002
Net cash provided by operating activities	73,692	92,204
INVESTING ACTIVITIES	'	'
Investment in operating properties - acquisitions	-37,635	0
Investment in operating properties - other	-16,522	-6,794
Investments in and advances to unconsolidated joint ventures	-429	-6,379
Distributions from unconsolidated joint ventures	2,978	1,871
Net proceeds from disposition of properties/land	327,160	71,909
Net proceeds from (advances on) public reimbursement receivable/escrow	5,001	8,500
Investment in development in progress	-74,478	-27,509
Investment in land held for development	-1,967	-3,493
Investment in deferred leasing costs	-9,158	-7,387
Net cash provided by investing activities	194,950	30,718
FINANCING ACTIVITIES	'	'
Net proceeds from issuance of common shares	15,472	44,927
Proceeds from mortgage loans	0	3,261
Repayments of mortgage loans	-2,019	-1,249
Proceeds from credit facility	0	19,600
Repayments on credit facility	0	-111,600
Increase in deferred financing costs	-3,619	-4
Distribution paid on common shares	-69,634	-56,274
Distribution paid on units	-1,914	-1,961
Net cash used in financing activities	-61,714	-103,300
Net increase in cash and cash equivalents	206,928	19,622
Increase (decrease) in cash and cash equivalents related to foreign currency translation	211	-3,544
Cash and cash equivalents at beginning of period	163,414	38,356
Cash and cash equivalents at end of period	370,553	54,434
Liberty Property Limited Partnership [Member]	'	'
OPERATING ACTIVITIES	'	'
Net income	74,106	74,656
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	57,589	45,585
Amortization of deferred financing costs	1,510	980
Equity in earnings of unconsolidated joint ventures	-4,159	-1,757
Distributions from unconsolidated joint ventures	0	265
Gain on property dispositions	-46,117	-41,713
Share-based compensation	6,580	4,445
Other	-635	-1,612
Changes in operating assets and liabilities:	'	'
Restricted cash	31,726	4,639
Accounts receivable	-4,052	642
Deferred rent receivable	-2,765	-3,246
Prepaid expenses and other assets	-26,557	1,319
Accounts payable	6,562	1,136
Accrued interest	16,441	18,867
Other liabilities	-36,537	-12,002
Net cash provided by operating activities	73,692	92,204
INVESTING ACTIVITIES	'	'
Investment in operating properties - acquisitions	-37,635	0
Investment in operating properties - other	-16,522	-6,794
Investments in and advances to unconsolidated joint ventures	-429	-6,379
Distributions from unconsolidated joint ventures	2,978	1,871
Net proceeds from disposition of properties/land	327,160	71,909
Net proceeds from (advances on) public reimbursement receivable/escrow	5,001	8,500
Investment in development in progress	-74,478	-27,509
Investment in land held for development	-1,967	-3,493
Investment in deferred leasing costs	-9,158	-7,387
Net cash provided by investing activities	194,950	30,718
FINANCING ACTIVITIES	'	'
Proceeds from mortgage loans	0	3,261
Repayments of mortgage loans	-2,019	-1,249
Proceeds from credit facility	0	19,600
Repayments on credit facility	0	-111,600
Increase in deferred financing costs	-3,619	-4
Capital contributions	15,472	44,927
Distributions to partners	71,548	58,235
Net cash used in financing activities	-61,714	-103,300
Net increase in cash and cash equivalents	206,928	19,622
Increase (decrease) in cash and cash equivalents related to foreign currency translation	211	-3,544
Cash and cash equivalents at beginning of period	163,414	38,356
Cash and cash equivalents at end of period	$370,553	$54,434

Organization_and_Basis_of_Pres

Organization and Basis of Presentation	3 Months Ended
	Mar. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	'
	Organization and Basis of Presentation
	Organization
	Liberty Property Trust (the “Trust”) is a self-administered and self-managed Maryland real estate investment trust (a “REIT”). Substantially all of the Trust’s assets are owned directly or indirectly, and substantially all of the Trust’s operations are conducted directly or indirectly, by its subsidiary, Liberty Property Limited Partnership, a Pennsylvania limited partnership (the “Operating Partnership” and, together with the Trust and their consolidated subsidiaries, the “Company”). The Trust is the sole general partner and also a limited partner of the Operating Partnership, owning 97.6% of the common equity of the Operating Partnership at March 31, 2014. The Company provides leasing, property management, development, acquisition, and other tenant-related services. The Company owns and operates industrial properties nationally and owns and operates office properties primarily in Metro Philadelphia, Washington D.C. and certain sunbelt cities. Additionally, the Company owns certain assets in the United Kingdom. Unless otherwise indicated, the notes to the Consolidated Financial Statements apply to both the Trust and the Operating Partnership. The terms the “Company,” “we,” “our” and “us” mean the Trust and Operating Partnership collectively.
	Basis of Presentation
	The accompanying unaudited consolidated financial statements of the Company have been prepared in accordance with United States generally accepted accounting principles (“US GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by US GAAP for complete financial statements and should be read in conjunction with the consolidated financial statements and notes thereto included in the Annual Report on Form 10-K of the Company for the year ended December 31, 2013. In the opinion of management, all adjustments (consisting solely of normal recurring adjustments) necessary for a fair presentation of the financial statements for these interim periods have been included. The results of interim periods are not necessarily indicative of the results to be obtained for a full fiscal year. Certain amounts from prior periods have been reclassified to conform to the current period presentation including reclassifying the accompanying statements of comprehensive income for discontinued operations.
	Recently Issued Accounting Standards
	In April 2014, the Financial Accounting Standards Board issued Accounting Standards Update (ASU) 2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360), Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity ("ASU 2014-08"), which changes the requirements for reporting discontinued operations. Under ASU 2014-08, a disposal of a component of an entity or a group of components of an entity is required to be reported in discontinued operations if the disposal represents a strategic shift that has (or will have) a major effect on an entity's operations and financial results when the component or group of components meets the criteria to be classified as held for sale or when the component or group of components is disposed of by sale or other than by sale. ASU 2014-08 also requires additional disclosures about both discontinued operations and the disposal of an individually significant component of an entity that does not qualify for discontinued operations presentation in the financial statements. The Company has adopted the provisions of ASU 2014-08 effective January 1, 2014, and has applied the provisions prospectively.

Income_per_Common_Share_of_the

Income per Common Share of the Trust	3 Months Ended
	Mar. 31, 2014
Income per Common Share of the Trust [Abstract]	'
Earnings Per Share [Text Block]	'
	Income per Common Share of the Trust
	The following table sets forth the computation of basic and diluted income per common share of the Trust (in thousands except per share amounts):
		For the Three Months Ended					For the Three Months Ended
		March 31, 2014					March 31, 2013
		Income		Weighted	Per Share		Income		Weighted	Per Share
		(Loss) (Numerator)		Average			(Numerator)		Average
				Shares					Shares
				(Denominator)					(Denominator)
	Basic income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	25,250	146,425	$	0.17	$	22,908	118,688	$	0.19
	Dilutive shares for long-term compensation plans	—		670			—		844
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	25,250	147,095	$	0.17	$	22,908	119,532	$	0.19
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	46,650	146,425	$	0.32	$	48,331	118,688	$	0.41
	Dilutive shares for long-term compensation plans	—		670			—		844
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	46,650	147,095	$	0.32	$	48,331	119,532	$	0.41
	Basic income per common share
	Net income available to common shareholders	$	71,900	146,425	$	0.49	$	71,239	118,688	$	0.6
	Dilutive shares for long-term compensation plans	—		670			—		844
	Diluted income per common share
	Net income available to common shareholders	$	71,900	147,095	$	0.49	$	71,239	119,532	$	0.6
	Dilutive shares for long-term compensation plans represent the unvested common shares outstanding during the periods as well as the dilutive effect of outstanding options. The amount of anti-dilutive options excluded from the computation of diluted income per common share for the three months ended March 31, 2014 was 1,247,000 as compared to 992,000 for the same period in 2013.
	During the three months ended March 31, 2014, 1,000 common shares were issued upon the exercise of options. During the year ended December 31, 2013, 504,000 common shares were issued upon the exercise of options.

Income_per_Common_Unit_of_the_

Income per Common Unit of the Operating Partnership	3 Months Ended
	Mar. 31, 2014
Income Per Common Unit [Line Items]	'
Earnings Per Share [Text Block]	'
	Income per Common Share of the Trust
	The following table sets forth the computation of basic and diluted income per common share of the Trust (in thousands except per share amounts):
		For the Three Months Ended						For the Three Months Ended
		March 31, 2014						March 31, 2013
		Income			Weighted	Per Share		Income			Weighted	Per Share
		(Loss) (Numerator)			Average			(Numerator)			Average
					Shares						Shares
					(Denominator)						(Denominator)
	Basic income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	25,250		146,425	$	0.17	$	22,908		118,688	$	0.19
	Dilutive shares for long-term compensation plans	—			670			—			844
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	25,250		147,095	$	0.17	$	22,908		119,532	$	0.19
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	46,650		146,425	$	0.32	$	48,331		118,688	$	0.41
	Dilutive shares for long-term compensation plans	—			670			—			844
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	46,650		147,095	$	0.32	$	48,331		119,532	$	0.41
	Basic income per common share
	Net income available to common shareholders	$	71,900		146,425	$	0.49	$	71,239		118,688	$	0.6
	Dilutive shares for long-term compensation plans	—			670			—			844
	Diluted income per common share
	Net income available to common shareholders	$	71,900		147,095	$	0.49	$	71,239		119,532	$	0.6
	Dilutive shares for long-term compensation plans represent the unvested common shares outstanding during the periods as well as the dilutive effect of outstanding options. The amount of anti-dilutive options excluded from the computation of diluted income per common share for the three months ended March 31, 2014 was 1,247,000 as compared to 992,000 for the same period in 2013.
	During the three months ended March 31, 2014, 1,000 common shares were issued upon the exercise of options. During the year ended December 31, 2013, 504,000 common shares were issued upon the exercise of options.
Liberty Property Limited Partnership [Member]	'
Income Per Common Unit [Line Items]	'
Earnings Per Share [Text Block]	'
	Income per Common Unit of the Operating Partnership
	The following table sets forth the computation of basic and diluted income per common unit of the Operating Partnership (in thousands, except per unit amounts):
		For the Three Months Ended						For the Three Months Ended
		March 31, 2014						March 31, 2013
		Income			Weighted	Per Unit		Income			Weighted	Per Unit
		(Loss) (Numerator)			Average Units			(Numerator)			Average Units
					(Denominator)						(Denominator)
	Income from continuing operations - net of noncontrolling interest - consolidated joint ventures	$	25,978					$	24,828
	Less: Preferred unit distributions	(118		)				(1,211		)
	Basic income from continuing operations
	Income from continuing operations available to common unitholders	$	25,860		149,981	$	0.17	$	23,617		122,402	$	0.19
	Dilutive units for long-term compensation plans	—			670			—			844
	Diluted income from continuing operations
	Income from continuing operations available to common unitholders	$	25,860		150,651	$	0.17	$	23,617		123,246	$	0.19
	Basic income from discontinued operations
	Discontinued operations	$	47,775		149,981	$	0.32	$	49,828		122,402	$	0.41
	Dilutive units for long-term compensation plans	—			670			—			844
	Diluted income from discontinued operations
	Discontinued operations	$	47,775		150,651	$	0.32	$	49,828		123,246	$	0.41
	Basic income per common unit
	Income available to common unitholders	$	73,635		149,981	$	0.49	$	73,445		122,402	$	0.6
	Dilutive units for long-term compensation plans	—			670			—			844
	Diluted income per common unit
	Income available to common unitholders	$	73,635		150,651	$	0.49	$	73,445		123,246	$	0.6
	Dilutive units for long-term compensation plans represent the unvested common units outstanding during the periods as well as the dilutive effect of outstanding options. The amount of anti-dilutive options excluded from the computation of diluted income per common unit for the three months ended March 31, 2014 was 1,247,000 as compared to 992,000 for the same period in 2013.
	During the three months ended March 31, 2014, 1,000 common units were issued upon the exercise of options. During the year ended December 31, 2013, 504,000 common units were issued upon the exercise of options.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income	3 Months Ended
	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]	'
Comprehensive Income (Loss) Note [Text Block]	'
	Accumulated Other Comprehensive Income (Loss)
	The following table sets forth the components of Accumulated Other Comprehensive Income (Loss) (in thousands):
		Three months ended March 31,
		2014			2013
	Foreign Currency Translation:
	Beginning balance	$	8,592		$	3,195
	Translation adjustment	1,346			(4,851		)
	Ending balance	9,938			(1,656		)
	Net unrealized gain (loss) on derivative instruments:
	Beginning balance	1,584			—
	Unrealized losses	(511		)	—
	Ending balance	1,073			—
	Total accumulated other comprehensive income	11,011			(1,656		)
	Less: portion included in noncontrolling interest – operating partnership	(454		)	(149		)
	Total accumulated other comprehensive income (loss) included in shareholders' equity	$	10,557		$	(1,805	)

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2014
Segment Reporting, Measurement Disclosures [Abstract]	'
Segment Information	'
	Segment Information
	The Company owns and operates industrial properties nationally and owns and operates office properties primarily in Metro Philadelphia, Washington D.C. and certain sunbelt cities. Additionally, the Company owns certain assets in the United Kingdom. The Company's reportable segments are as follows.
	•	Carolinas;
	•	Chicago/Milwaukee;
	•	Houston;
	•	Lehigh/Central PA;
	•	Minnesota;
	•	Orlando;
	•	Philadelphia;
	•	Richmond/Hampton Roads;
	•	Southeastern PA;
	•	South Florida;
	•	Tampa;
	•	United Kingdom.
	Certain other segments are aggregated into an "Other" category which includes the reportable segments: Arizona; Atlanta; Cincinnati/Columbus/Indianapolis; Dallas; Jacksonville; Maryland; New Jersey; Northern Virginia; Southern California; Washington D.C. and other.
	The Company evaluates the performance of its reportable segments based on net operating income. Net operating income includes operating revenue from external customers, real estate taxes, amortization of lease transaction costs and other operating expenses which relate directly to the management and operation of the assets within each reportable segment.
	The Company's accounting policies for the segments are the same as those used in the Company's consolidated financial statements. There are no material inter-segment transactions.
	The operating information by reportable segment is as follows (in thousands):
				For the Three Months
				Ended March 31,
				2014				2013
	Operating revenue
		Carolinas		$	8,316			$	7,279
		Chicago/Milwaukee		8,570				2,693
		Houston		11,867				8,334
		Lehigh/Central PA		29,623				24,677
		Minnesota		13,750				15,383
		Orlando		7,995				7,696
		Philadelphia		9,408				8,333
		Richmond/Hampton Roads		10,068				10,146
		South Florida		12,309				8,558
		Southeastern PA		38,437				41,054
		Tampa		13,173				12,963
		United Kingdom		4,102				1,100
		Other		35,039				29,735
	Segment-level operating revenue			202,657				177,951
	Reconciliation to total operating revenues
		Discontinued operations		(4,763		)		(31,080		)
		Other		(279		)		256
	Total operating revenue			$	197,615			$	147,127
	Net operating income
		Carolinas		$	5,742			$	4,914
		Chicago/Milwaukee		5,163				2,174
		Houston		7,053				5,250
		Lehigh/Central PA		19,240				16,668
		Minnesota		6,619				7,712
		Orlando		5,492				5,251
		Philadelphia		6,721				5,879
		Richmond/Hampton Roads		5,920				6,226
		South Florida		7,527				4,575
		Southeastern PA		19,600				22,613
		Tampa		8,441				8,254
		United Kingdom		3,526				(133		)
		Other		21,731				17,123
	Segment-level net operating income			122,775				106,506
	Reconciliation to income from continuing operations
		Interest expense (1)		(39,764		)		(32,082		)
		Depreciation/amortization expense (2)		(44,536		)		(29,307		)
		Equity in earnings of unconsolidated joint ventures		4,159				1,757
		General and administrative expense (2)		(12,401		)		(13,877		)
		Discontinued operations excluding gain on property dispositions		(1,658		)		(8,115		)
		Income taxes (2)		(483		)		(491		)
		Other		(1,761		)		437
Income from continuing operations			$	26,331			$	24,828
-1	Includes interest on discontinued operations.
-2	Excludes costs which are included in determining segment-level net operating income.
The Company's total assets by reportable segment as of March 31, 2014 and December 31, 2013 is as follows (in thousands):
		March 31,				December 31,
		2014				2013
Total assets
	Carolinas	$	260,502			$	257,230
	Chicago/Milwaukee	411,677				413,585
	Houston	389,279				380,248
	Lehigh/Central PA	952,396				938,824
	Minnesota	339,772				335,613
	Orlando	253,311				253,888
	Philadelphia	323,098				316,810
	Richmond/Hampton Roads	248,580				250,008
	South Florida	378,121				380,138
	Southeastern PA	695,294				695,966
	Tampa	335,984				337,300
	United Kingdom	261,819				247,537
	Other	1,501,146				1,735,393
Segment-level total assets		6,350,979				6,542,540
	Corporate Other	411,685				233,020
Total assets		$	6,762,664			$	6,775,560

Accounting_for_the_Impairment_

Accounting for the Impairment or Disposal of Long-Lived Assets	3 Months Ended
	Mar. 31, 2014
Accounting for the Impairment or Disposal of Long-Lived Assets [Abstract]	'
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	'
	Accounting for the Disposal of Long-Lived Assets
	Under ASU 2014-08, a disposal of a component of an entity is required to be reported in discontinued operations if the disposal represents a strategic shift that has (or will have) a major effect on an entity's operations and financial results.
	In November 2013, the Company entered into an Agreement of Sale and Purchase pursuant to which the Company agreed to sell 97 operating properties containing an aggregate of 6.6 million square feet for $697.3 million (the "Portfolio Sale"). In December 2013, the Company closed on the first of two planned settlements under this agreement. The proceeds from the first settlement were $367.7 million and included 49 properties totaling approximately 4.0 million square feet of space and 140 acres of land. In January 2014, the Company closed on the remaining settlement for proceeds of $329.6 million which consisted of 23 properties totaling 1.4 million square feet and 19 acres of land in the Maryland reportable segment, 24 properties and 1.2 million square feet in the New Jersey reportable segment and one property totaling 37,000 square feet in the Company's Southeastern PA reportable segment.
	The Portfolio Sale is considered a discontinued operation under the provisions of ASU 2014-08 as it represents a strategic shift that will have a major effect on the Company's operations and financial results.
	Prior to the adoption of ASU 2014-08, the results of operations for all operating properties sold or held for sale during the reported periods were shown under discontinued operations on the consolidated statements of comprehensive income. Under ASU 2014-08, operating properties that were sold or classified as held for sale before the adoption of ASU 2014-08 continue to be classified as discontinued operations. Accordingly, operating properties previously reported as discontinued operations will continue to be presented as discontinued operations on the consolidated statements of comprehensive income for all periods presented. The proceeds from the distribution of properties besides the Portfolio Sale that were included in discontinued operations was zero for the three months ended March 31, 2014 and was $74.7 million for the three months ended March 31, 2013.
	A summary of the results of operations for the Portfolio Sale and other properties classified as discontinued operations through the respective disposition dates is as follows (in thousands):
			For the Three Months Ended
			March 31, 2014			March 31, 2013
	Portfolio Sale
		Revenues	$	4,763		$	27,140
		Operating expenses	(2,570		)	(9,433		)
		Interest and other income	22			49
		Interest expense	(557		)	(3,772		)
		Depreciation and amortization	—			(7,311		)
		Income before gain on property dispositions	1,658			6,673
		Gain on property dispositions	46,074			—
		Income from discontinued operations - Portfolio Sale	$	47,732		$	6,673
		Noncontrolling interest	(1,125		)	(200		)
		Income from discontinued operations available to common shareholders - Portfolio Sale	$	46,607		$	6,473
		Add back noncontrolling interest	1,125			$	200
		Income from discontinued operations - Portfolio Sale	$	47,732		$	6,673
		Income from discontinued operations - other properties	43			43,155
		Income from discontinued operations	$	47,775		$	49,828
	Net cash used in operating activities from the properties included in the Portfolio Sale for the three months ended March 31, 2014 was $2.7 million compared to net cash provided by operating activities from such properties of $14.7 million for the three months ended March 31, 2013. Net cash provided by investing activities from the properties included in the Portfolio Sale for the three months ended March 31, 2014 was $313.1 million compared to net cash used by investing activities from such properties of $3.8 million for the three months ended March 31, 2013.
	Interest expense has been allocated to discontinued operations. The allocation of interest expense to discontinued operations was based on the ratio of net assets sold and held for sale (without continuing involvement) to the sum of total net assets plus consolidated debt.

Noncontrolling_Interests

Noncontrolling Interests	3 Months Ended
	Mar. 31, 2014
Stockholders' Equity Attributable to Noncontrolling Interest [Abstract]	'
Noncontrolling Interests	'
	Noncontrolling Interests of the Trust
	Noncontrolling interests in the accompanying financial statements represent the interests of the common and preferred units in the Operating Partnership not held by the Trust. In addition, noncontrolling interests include third-party ownership interests in consolidated joint venture investments.
	Common units
	The common units outstanding of the Operating Partnership not held by the Trust as of March 31, 2014 have the same economic characteristics as common shares of the Trust. The 3,553,566 outstanding common units of the Operating Partnership at such date not held by the Trust share proportionately in the net income or loss and in any distributions of the Operating Partnership. The common units of the Operating Partnership not held by the Trust are redeemable at any time at the option of the holder. The Trust, as the sole general partner of the Operating Partnership, may at its option elect to settle the redemption in cash or through the exchange on a one-for-one basis with unregistered common shares of the Trust. The market value of the 3,553,566 outstanding common units based on the closing price of the common shares of the Trust at March 31, 2014 was $131.3 million.

Limited_Partners_Equity_of_the

Limited Partners' Equity of the Operating Partnership	3 Months Ended
	Mar. 31, 2014
Preferred Units [Line Items]	'
Noncontrolling Interest Disclosure [Text Block]	'
	Noncontrolling Interests of the Trust
	Noncontrolling interests in the accompanying financial statements represent the interests of the common and preferred units in the Operating Partnership not held by the Trust. In addition, noncontrolling interests include third-party ownership interests in consolidated joint venture investments.
	Common units
	The common units outstanding of the Operating Partnership not held by the Trust as of March 31, 2014 have the same economic characteristics as common shares of the Trust. The 3,553,566 outstanding common units of the Operating Partnership at such date not held by the Trust share proportionately in the net income or loss and in any distributions of the Operating Partnership. The common units of the Operating Partnership not held by the Trust are redeemable at any time at the option of the holder. The Trust, as the sole general partner of the Operating Partnership, may at its option elect to settle the redemption in cash or through the exchange on a one-for-one basis with unregistered common shares of the Trust. The market value of the 3,553,566 outstanding common units based on the closing price of the common shares of the Trust at March 31, 2014 was $131.3 million.
Liberty Property Limited Partnership [Member]	'
Preferred Units [Line Items]	'
Noncontrolling Interest Disclosure [Text Block]	'
	Limited Partners' Equity and Noncontrolling Interest of the Operating Partnership
	Limited partners' equity in the accompanying financial statements represents the interests of the common and preferred units in the Operating Partnership not held by the Trust. The Operating Partnership's noncontrolling interest includes third-party ownership interests in consolidated joint venture investments.
	Common units
	The common units outstanding as of March 31, 2014 have the same economic characteristics as common shares of the Trust. The 3,553,566 outstanding common units at such date are the limited partners' equity - common units held by persons and entities other than the Trust, the general partner of the Operating Partnership, which holds a number of common units equal to the number of outstanding common shares of beneficial interest. Both the common units held by the Trust and the common units held by persons and entities other than the Trust are counted in the weighted average number of common units outstanding during any given period. The common units share proportionately in the net income or loss and in any distributions of the Operating Partnership and are exchangeable into the same number of common shares of the Trust. The market value of the 3,553,566 outstanding common units at March 31, 2014 based on the closing price of the common shares of the Trust at March 31, 2014 was $131.3 million.

Noncontrolling_Interest_Operat

Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units	3 Months Ended
	Mar. 31, 2014
Limited Partners' Capital Account - Preferred Units [Line Items]	'
Schedule of Limited Partners' Capital Account by Class [Table Text Block]	'
	Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units
	As of March 31, 2014, the following cumulative preferred units of the Operating Partnership were outstanding:
	ISSUE	AMOUNT		UNITS	LIQUIDATION	DIVIDEND
					PREFERENCE	RATE
		(in 000’s)
	Series I-2	$	7,537	301	$25	6.25	%
	The preferred units are putable at the holder's option at any time and are callable at the Operating Partnership's option after a stated period of time for cash.

Indebtedness

Indebtedness	3 Months Ended
	Mar. 31, 2014
Debt Disclosure [Abstract]	'
Debt Disclosure [Text Block]	'
	Indebtedness
	Credit Facility
	In March 2014, The Company replaced its existing $500 million credit facility which was due in November 2015 with a new credit facility. The new facility (the "Credit Facility") is for $800 million. It matures in March 2018 and the Company has options to extend the maturity date for up to one additional year. Based upon the Company’s current credit ratings, borrowings under the new facility bear interest at LIBOR plus 105 basis points. There is also a 20 basis point annual facility fee on the current borrowing capacity. The credit facility contains a competitive bid option, whereby participating lenders bid on the interest rate to be charged. This feature is available for up to 50% of the amount of the facility.
	The Credit Facility contains financial covenants, certain of which are set forth below:
	•	total debt to total assets may not exceed 0.60:1;
	•	earnings before interest, taxes, depreciation and amortization to fixed charges may not be less than 1.50:1;
	•	unsecured debt to unencumbered asset value must equal or be less than 60%; and
	•	unencumbered net operating income to unsecured interest expense must equal or exceed 175%.
	As of March 31, 2014, the Company was in compliance with the Credit Facility financial covenants.

Disclosure_of_Fair_Value_of_Fi

Disclosure of Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2014
Debt Instrument, Fair Value Disclosure [Abstract]	'
Disclosure of Fair Value of Financial Instruments	'
	Disclosure of Fair Value of Financial Instruments
	The following disclosure of estimated fair value was determined by management using available market information and appropriate valuation methodologies. However, considerable judgment is necessary to interpret market data and develop estimated fair value. Accordingly, the following estimates are not necessarily indicative of the amounts the Company could have realized on disposition of the financial instruments at March 31, 2014 and December 31, 2013. The use of different market assumptions and/or estimation methodologies may have a material effect on the estimated fair value amounts.
	The carrying value of cash and cash equivalents, restricted cash, accounts receivable, accounts payable, accrued interest, dividend and distributions payable and other liabilities are reasonable estimates of fair value because of the short-term nature of these instruments.
	The Company used a discounted cash flow model to determine the estimated fair value of its debt as of March 31, 2014.  This is a Level 3 fair value calculation. The inputs used in preparing the discounted cash flow model include actual maturity dates and scheduled cash flows as well as estimates for market value discount rates.  The Company updates the discounted cash flow model on a quarterly basis to reflect any changes in the Company's debt holdings and changes to discount rate assumptions.
	The following summarizes the fair value of the Company's mortgage loans and unsecured notes as of December 31, 2013 and March 31, 2014 (in thousands):
		Mortgage Loans				Unsecured Notes
		Carrying Value		Fair Value		Carrying Value		Fair Value
	As of December 31, 2013	$	545,306	$	573,944	$	2,708,213	$	2,764,831
	As of March 31, 2014	$	542,809	$	569,140	$	2,708,440	$	2,830,329

Business_Combination

Business Combination	3 Months Ended
	Mar. 31, 2014
Business Combinations [Abstract]	'
Business Combination Disclosure [Text Block]	'
	Business Combination
	On October 8, 2013, the Company acquired all of the outstanding general and limited partnership interests of Cabot Industrial Fund III Operating Partnership, L.P., a Delaware limited partnership (the "Cabot Acquisition"). The acquisition resulted in the purchase of a 100% ownership interest in 177 industrial assets totaling approximately 23.0 million square feet. The purchase price for the Cabot Acquisition was $1.469 billion, which was paid through the assumption of approximately $229.8 million of mortgage debt and the remainder in cash. The Company funded the cash portion of the acquisition consideration through a combination of proceeds from an August 2013 equity offering, proceeds from a September 2013 offering of senior notes and draws under its Credit Facility.
	The allocation of purchase price of the Cabot Acquisition is preliminary pending the receipt of the information necessary to complete the resolution of certain tangible and intangible assets and liabilities including the reconciliation of working capital accounts and the completion of tenant operating expense reconciliations.

Derivative_Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Interest rate swaps [Text Block]	'
	Derivative Instruments
	We borrow funds at a combination of fixed and variable rates. Borrowings under our revolving credit facility and certain bank mortgage loans bear interest at variable rates. Our long-term debt typically bears interest at fixed rates. Our interest rate risk management objectives are to limit generally the impact of interest rate changes on earnings and cash flows and to lower our overall borrowing costs. To achieve these objectives, from time to time, we enter into interest rate hedge contracts such as collars, swaps, caps and treasury lock agreements in order to mitigate our interest rate risk with respect to various debt instruments. We generally do not hold or issue these derivative contracts for trading or speculative purposes. The interest rate on all of our variable rate debt is generally adjusted at one or three month intervals, subject to settlements under interest rate hedge contracts.
	Interest rate swaps involve the receipt of variable-rate amounts from a counterparty in exchange for making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive income (for the Trust) and general partner's equity and limited partners' equity - common units (for the Operating Partnership) and is subsequently reclassified into interest expense in the period that the hedged forecasted transaction affects earnings.
	In connection with the Cabot Acquisition, the Company assumed the seller’s interest in three interest rate swap contracts (“Swaps”) that eliminate the impact of changes in interest rates on the payments required under variable rate mortgages that were also assumed. The Swaps had aggregate notional amounts of $104.9 million and $105.2 million at March 31, 2014 and December 31, 2013, respectively, and expire at various dates between 2018 and 2020.
	For the three months ended March 31, 2014, the effective portion of the change in the fair value of the swaps was a decrease in the amount of $871,000, which was recorded as a reduction of other comprehensive income and will be reclassified into earnings as a component of interest expense in the period that the hedged forecasted transaction affects earnings. The amount of loss reclassified into interest expense from accumulated other comprehensive income was $360,000 for the three months ended March 31, 2014. The ineffective portion of the change in the fair value of the Swaps for the three months ended March 31, 2014 in the amount of $18,000 was recorded as an increase to interest expense in the accompanying consolidated statements of comprehensive income.
	The fair value of the Swaps in the amount of $8.4 million as of both March 31, 2014 and December 31, 2013 is included in other liabilities in the accompanying consolidated balance sheets. The Company estimates that $1.4 million will be reclassified from accumulated other comprehensive income as an increase to interest expense over the next twelve months.
	The Company has agreements with its derivative counterparties that contain a provision whereby if the Company defaults on any of its indebtedness, including default where repayment of the indebtedness has not been accelerated by the lender, then the Company could also be declared in default on its derivative obligations. If the Company were to breach any of the contractual provisions of the derivative contracts, it would be required to settle its obligations under the agreements at their termination value including accrued interest for approximately $8.8 million.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2014
Commitments and Contingencies [Abstract]	'
Commitments and Contingencies	'
	Commitments and Contingencies
	Environmental Matters
	Substantially all of the Company's properties and land were subject to Phase I Environmental Assessments and when appropriate Phase II Environmental Assessments (collectively, the “Environmental Assessments”) obtained in contemplation of their acquisition by the Company or obtained by predecessor owners prior to the sale of the property or land to the Company. The Environmental Assessments did not reveal, nor is the Company aware of, any non-compliance with environmental laws, environmental liability or other environmental claim that the Company believes would likely have a material adverse effect on the Company.
	Operating Ground Lease Agreements
	Future minimum rental payments under the terms of all non-cancelable operating ground leases under which the Company is the lessee, as of March 31, 2014, were as follows (in thousands):
	Year	Amount
	2014	$	274
	2015	384
	2016	403
	2017	403
	2018	403
	2019 through 2034	5,575
	Total	$	7,442
	Operating ground lease expense for the three months ended March 31, 2014 was $47,000 as compared to $40,000 for the same period in 2013.
	Legal Matters
	From time to time, the Company is a party to a variety of legal proceedings, claims and assessments arising in the normal course of business. As of March 31, 2014 there were no legal proceedings, claims or assessments that the Company expects to have a material adverse effect on the Company’s business or financial statements.
	Other
	As of March 31, 2014, the Company had letter of credit obligations of $8.1 million. The Company believes that the likelihood is remote that there will be a draw upon these letter of credit obligations.
	As of March 31, 2014, the Company had 15 buildings under development. These buildings are expected to contain, when completed, a total of 4.9 million square feet of leasable space and represent an anticipated aggregate investment of $406.1 million. At March 31, 2014, development in progress totaled $242.8 million. In addition, as of March 31, 2014, the Company had invested $10.8 million in deferred leasing costs related to these development buildings. Also, as of March 31, 2014, the Company had a signed commitment for a development building not yet commenced for $12.7 million.
	As of March 31, 2014, the Company was committed to $12.8 million in improvements on certain buildings and land parcels.
	As of March 31, 2014, the Company was committed to $52.8 million in future land purchases.
	As of March 31, 2014, the Company was obligated to pay for tenant improvements not yet completed for a maximum of $36.3 million.
	The Company maintains cash and cash equivalents at financial institutions. The combined account balances at each institution typically exceed FDIC insurance coverage and, as a result, there is a concentration of credit risk related to amounts on deposit in excess of FDIC insurance coverage. The Company believes the risk is not significant.

Supplemental_Disclosure_to_Sta

Supplemental Disclosure to Statements of Cash Flows	3 Months Ended
	Mar. 31, 2014
Supplemental Cash Flow Information [Abstract]	'
Supplemental Disclosure to Statements of Cash Flows	'
	Supplemental Disclosure to Statements of Cash Flows
	The following are supplemental disclosures to the statements of cash flows for the three months ended March 31, 2014 and 2013 (amounts in thousands):
		2014			2013
	Write-off of fully depreciated property and deferred costs	$	11,279		$	7,182
	Write-off of depreciated property and deferred costs due to sale	$	131,026		$	23,906
	Unrealized losses on cash flow hedge	$	(511	)	$	—
	Amounts paid in cash for deferred leasing costs incurred in connection with signed leases with tenants are paid in conjunction with improving (acquiring) property, plant and equipment. Such costs are not contained within net real estate. However, they are integral to the completion of a tenant lease and ultimately are related to the improvement and thus the value of the Company’s property, plant and equipment. They are therefore included in investing activities in the Company’s consolidated statements of cash flows.

Organization_and_Basis_of_Pres1

Organization and Basis of Presentation (Policy)	3 Months Ended
	Mar. 31, 2014
Organization and Basis of Presentation [Abstract]	'
Organization	'
	Organization
	Liberty Property Trust (the “Trust”) is a self-administered and self-managed Maryland real estate investment trust (a “REIT”). Substantially all of the Trust’s assets are owned directly or indirectly, and substantially all of the Trust’s operations are conducted directly or indirectly, by its subsidiary, Liberty Property Limited Partnership, a Pennsylvania limited partnership (the “Operating Partnership” and, together with the Trust and their consolidated subsidiaries, the “Company”). The Trust is the sole general partner and also a limited partner of the Operating Partnership, owning 97.6% of the common equity of the Operating Partnership at March 31, 2014. The Company provides leasing, property management, development, acquisition, and other tenant-related services. The Company owns and operates industrial properties nationally and owns and operates office properties primarily in Metro Philadelphia, Washington D.C. and certain sunbelt cities. Additionally, the Company owns certain assets in the United Kingdom. Unless otherwise indicated, the notes to the Consolidated Financial Statements apply to both the Trust and the Operating Partnership. The terms the “Company,” “we,” “our” and “us” mean the Trust and Operating Partnership collectively.
Basis of Presentation	'
	Basis of Presentation
	The accompanying unaudited consolidated financial statements of the Company have been prepared in accordance with United States generally accepted accounting principles (“US GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by US GAAP for complete financial statements and should be read in conjunction with the consolidated financial statements and notes thereto included in the Annual Report on Form 10-K of the Company for the year ended December 31, 2013. In the opinion of management, all adjustments (consisting solely of normal recurring adjustments) necessary for a fair presentation of the financial statements for these interim periods have been included. The results of interim periods are not necessarily indicative of the results to be obtained for a full fiscal year. Certain amounts from prior periods have been reclassified to conform to the current period presentation including reclassifying the accompanying statements of comprehensive income for discontinued operations.

Income_per_Common_Share_of_the1

Income per Common Share of the Trust (Tables)	3 Months Ended
	Mar. 31, 2014
Income per Common Share of the Trust [Abstract]	'
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	'
	The following table sets forth the computation of basic and diluted income per common share of the Trust (in thousands except per share amounts):
		For the Three Months Ended					For the Three Months Ended
		March 31, 2014					March 31, 2013
		Income		Weighted	Per Share		Income		Weighted	Per Share
		(Loss) (Numerator)		Average			(Numerator)		Average
				Shares					Shares
				(Denominator)					(Denominator)
	Basic income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	25,250	146,425	$	0.17	$	22,908	118,688	$	0.19
	Dilutive shares for long-term compensation plans	—		670			—		844
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	25,250	147,095	$	0.17	$	22,908	119,532	$	0.19
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	46,650	146,425	$	0.32	$	48,331	118,688	$	0.41
	Dilutive shares for long-term compensation plans	—		670			—		844
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	46,650	147,095	$	0.32	$	48,331	119,532	$	0.41
	Basic income per common share
	Net income available to common shareholders	$	71,900	146,425	$	0.49	$	71,239	118,688	$	0.6
	Dilutive shares for long-term compensation plans	—		670			—		844
	Diluted income per common share
	Net income available to common shareholders	$	71,900	147,095	$	0.49	$	71,239	119,532	$	0.6

Income_per_Common_Unit_of_the_1

Income per Common Unit of the Operating Partnership (Tables)	3 Months Ended
	Mar. 31, 2014
Income Per Common Unit [Line Items]	'
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	'
	The following table sets forth the computation of basic and diluted income per common share of the Trust (in thousands except per share amounts):
		For the Three Months Ended						For the Three Months Ended
		March 31, 2014						March 31, 2013
		Income			Weighted	Per Share		Income			Weighted	Per Share
		(Loss) (Numerator)			Average			(Numerator)			Average
					Shares						Shares
					(Denominator)						(Denominator)
	Basic income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	25,250		146,425	$	0.17	$	22,908		118,688	$	0.19
	Dilutive shares for long-term compensation plans	—			670			—			844
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	25,250		147,095	$	0.17	$	22,908		119,532	$	0.19
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	46,650		146,425	$	0.32	$	48,331		118,688	$	0.41
	Dilutive shares for long-term compensation plans	—			670			—			844
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	46,650		147,095	$	0.32	$	48,331		119,532	$	0.41
	Basic income per common share
	Net income available to common shareholders	$	71,900		146,425	$	0.49	$	71,239		118,688	$	0.6
	Dilutive shares for long-term compensation plans	—			670			—			844
	Diluted income per common share
	Net income available to common shareholders	$	71,900		147,095	$	0.49	$	71,239		119,532	$	0.6
Liberty Property Limited Partnership [Member]	'
Income Per Common Unit [Line Items]	'
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	'
	The following table sets forth the computation of basic and diluted income per common unit of the Operating Partnership (in thousands, except per unit amounts):
		For the Three Months Ended						For the Three Months Ended
		March 31, 2014						March 31, 2013
		Income			Weighted	Per Unit		Income			Weighted	Per Unit
		(Loss) (Numerator)			Average Units			(Numerator)			Average Units
					(Denominator)						(Denominator)
	Income from continuing operations - net of noncontrolling interest - consolidated joint ventures	$	25,978					$	24,828
	Less: Preferred unit distributions	(118		)				(1,211		)
	Basic income from continuing operations
	Income from continuing operations available to common unitholders	$	25,860		149,981	$	0.17	$	23,617		122,402	$	0.19
	Dilutive units for long-term compensation plans	—			670			—			844
	Diluted income from continuing operations
	Income from continuing operations available to common unitholders	$	25,860		150,651	$	0.17	$	23,617		123,246	$	0.19
	Basic income from discontinued operations
	Discontinued operations	$	47,775		149,981	$	0.32	$	49,828		122,402	$	0.41
	Dilutive units for long-term compensation plans	—			670			—			844
	Diluted income from discontinued operations
	Discontinued operations	$	47,775		150,651	$	0.32	$	49,828		123,246	$	0.41
	Basic income per common unit
	Income available to common unitholders	$	73,635		149,981	$	0.49	$	73,445		122,402	$	0.6
	Dilutive units for long-term compensation plans	—			670			—			844
	Diluted income per common unit
	Income available to common unitholders	$	73,635		150,651	$	0.49	$	73,445		123,246	$	0.6

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]	'
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	'
	The following table sets forth the components of Accumulated Other Comprehensive Income (Loss) (in thousands):
		Three months ended March 31,
		2014			2013
	Foreign Currency Translation:
	Beginning balance	$	8,592		$	3,195
	Translation adjustment	1,346			(4,851		)
	Ending balance	9,938			(1,656		)
	Net unrealized gain (loss) on derivative instruments:
	Beginning balance	1,584			—
	Unrealized losses	(511		)	—
	Ending balance	1,073			—
	Total accumulated other comprehensive income	11,011			(1,656		)
	Less: portion included in noncontrolling interest – operating partnership	(454		)	(149		)
	Total accumulated other comprehensive income (loss) included in shareholders' equity	$	10,557		$	(1,805	)

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2014
Segment Reporting, Measurement Disclosures [Abstract]	'
Schedule of Segment Reporting Information, by Segment, Revenue and Net Operating Income [Table Text Block]	'
	The operating information by reportable segment is as follows (in thousands):
				For the Three Months
				Ended March 31,
				2014				2013
	Operating revenue
		Carolinas		$	8,316			$	7,279
		Chicago/Milwaukee		8,570				2,693
		Houston		11,867				8,334
		Lehigh/Central PA		29,623				24,677
		Minnesota		13,750				15,383
		Orlando		7,995				7,696
		Philadelphia		9,408				8,333
		Richmond/Hampton Roads		10,068				10,146
		South Florida		12,309				8,558
		Southeastern PA		38,437				41,054
		Tampa		13,173				12,963
		United Kingdom		4,102				1,100
		Other		35,039				29,735
	Segment-level operating revenue			202,657				177,951
	Reconciliation to total operating revenues
		Discontinued operations		(4,763		)		(31,080		)
		Other		(279		)		256
	Total operating revenue			$	197,615			$	147,127
	Net operating income
		Carolinas		$	5,742			$	4,914
		Chicago/Milwaukee		5,163				2,174
		Houston		7,053				5,250
		Lehigh/Central PA		19,240				16,668
		Minnesota		6,619				7,712
		Orlando		5,492				5,251
		Philadelphia		6,721				5,879
		Richmond/Hampton Roads		5,920				6,226
		South Florida		7,527				4,575
		Southeastern PA		19,600				22,613
		Tampa		8,441				8,254
		United Kingdom		3,526				(133		)
		Other		21,731				17,123
	Segment-level net operating income			122,775				106,506
	Reconciliation to income from continuing operations
		Interest expense (1)		(39,764		)		(32,082		)
		Depreciation/amortization expense (2)		(44,536		)		(29,307		)
		Equity in earnings of unconsolidated joint ventures		4,159				1,757
		General and administrative expense (2)		(12,401		)		(13,877		)
		Discontinued operations excluding gain on property dispositions		(1,658		)		(8,115		)
		Income taxes (2)		(483		)		(491		)
		Other		(1,761		)		437
	Income from continuing operations			$	26,331			$	24,828
	-1	Includes interest on discontinued operations.
	-2	Excludes costs which are included in determining segment-level net operating income.
Reconciliation of Assets from Segment to Consolidated [Table Text Block]	'
	The Company's total assets by reportable segment as of March 31, 2014 and December 31, 2013 is as follows (in thousands):
			March 31,				December 31,
			2014				2013
	Total assets
		Carolinas	$	260,502			$	257,230
		Chicago/Milwaukee	411,677				413,585
		Houston	389,279				380,248
		Lehigh/Central PA	952,396				938,824
		Minnesota	339,772				335,613
		Orlando	253,311				253,888
		Philadelphia	323,098				316,810
		Richmond/Hampton Roads	248,580				250,008
		South Florida	378,121				380,138
		Southeastern PA	695,294				695,966
		Tampa	335,984				337,300
		United Kingdom	261,819				247,537
		Other	1,501,146				1,735,393
	Segment-level total assets		6,350,979				6,542,540
		Corporate Other	411,685				233,020
	Total assets		$	6,762,664			$	6,775,560

Accounting_for_the_Impairment_1

Accounting for the Impairment or Disposal of Long-Lived Assets (Tables)	3 Months Ended
	Mar. 31, 2014
Accounting for the Impairment or Disposal of Long-Lived Assets [Abstract]	'
Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures [Table Text Block]	'
	A summary of the results of operations for the Portfolio Sale and other properties classified as discontinued operations through the respective disposition dates is as follows (in thousands):
			For the Three Months Ended
			March 31, 2014			March 31, 2013
	Portfolio Sale
		Revenues	$	4,763		$	27,140
		Operating expenses	(2,570		)	(9,433		)
		Interest and other income	22			49
		Interest expense	(557		)	(3,772		)
		Depreciation and amortization	—			(7,311		)
		Income before gain on property dispositions	1,658			6,673
		Gain on property dispositions	46,074			—
		Income from discontinued operations - Portfolio Sale	$	47,732		$	6,673
		Noncontrolling interest	(1,125		)	(200		)
		Income from discontinued operations available to common shareholders - Portfolio Sale	$	46,607		$	6,473
		Add back noncontrolling interest	1,125			$	200
		Income from discontinued operations - Portfolio Sale	$	47,732		$	6,673
		Income from discontinued operations - other properties	43			43,155
		Income from discontinued operations	$	47,775		$	49,828

Noncontrolling_Interest_Operat1

Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units (Tables)	3 Months Ended
	Mar. 31, 2014
Limited Partners' Capital Account - Preferred Units [Line Items]	'
Schedule of Preferred Units [Table Text Block]	'
	ISSUE	AMOUNT		UNITS	LIQUIDATION	DIVIDEND
					PREFERENCE	RATE
		(in 000’s)
	Series I-2	$	7,537	301	$25	6.25	%

Disclosure_of_Fair_Value_of_Fi1

Disclosure of Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2014
Debt Instrument, Fair Value Disclosure [Abstract]	'
Fair Value, by Balance Sheet Grouping [Table Text Block]	'
	The following summarizes the fair value of the Company's mortgage loans and unsecured notes as of December 31, 2013 and March 31, 2014 (in thousands):
		Mortgage Loans				Unsecured Notes
		Carrying Value		Fair Value		Carrying Value		Fair Value
	As of December 31, 2013	$	545,306	$	573,944	$	2,708,213	$	2,764,831
	As of March 31, 2014	$	542,809	$	569,140	$	2,708,440	$	2,830,329

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2014
Commitments and Contingencies [Abstract]	'
Future Minimum Rental Payments	'
	Year	Amount
	2014	$	274
	2015	384
	2016	403
	2017	403
	2018	403
	2019 through 2034	5,575
	Total	$	7,442

Supplemental_Disclosure_to_Sta1

Supplemental Disclosure to Statements of Cash Flows (Tables)	3 Months Ended
	Mar. 31, 2014
Supplemental Cash Flow Information [Abstract]	'
Supplemental Disclosure to Statements of Cash Flows	'
		2014			2013
	Write-off of fully depreciated property and deferred costs	$	11,279		$	7,182
	Write-off of depreciated property and deferred costs due to sale	$	131,026		$	23,906
	Unrealized losses on cash flow hedge	$	(511	)	$	—

Organization_and_Basis_of_Pres2

Organization and Basis of Presentation (Narrative) (Details)	Mar. 31, 2014
Organization and Basis of Presentation [Abstract]	'
Ownership interest in operating partnership - Limited Partnership	97.60%

Income_per_Common_Share_of_the2

Income per Common Share of the Trust (Details) (USD $)	3 Months Ended		12 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Income per Common Share of the Trust [Abstract]	'	'	'
Income from continuing operations net of noncontrolling interest	$25,250	$22,908	'
Weighted Average Number of Shares Outstanding, Basic	146,425,000	118,688,000	'
Income from Continuing Operations, Per Basic Share	$0.17	$0.19	'
Dilutive shares for long-term compensation plans	670,000	844,000	'
Weighted Average Number of Shares Outstanding, Diluted	147,095,000	119,532,000	'
Income from Continuing Operations, Per Diluted Share	$0.17	$0.19	'
Income from Discontinued Operations, Net of Tax, Attributable to Parent	46,650	48,331	'
Income from Discontinued Operations, Net of Tax, Per Basic Share	$0.32	$0.41	'
Discontinued operations net of noncontrolling interest, Per Diluted Share	$0.32	$0.41	'
Net Income Available to Common Stockholders, Basic	$71,900	$71,239	'
Earnings Per Share, Basic	$0.49	$0.60	'
Earnings Per Share, Diluted	$0.49	$0.60	'
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,247,000	992,000	'
Stock Issued During Period, Shares, Stock Options Exercised	1,000	'	504,000

Income_per_Common_Unit_of_the_2

Income per Common Unit of the Operating Partnership (Details) (USD $)	3 Months Ended		12 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Income Per Common Unit [Line Items]	'	'	'
Income from continuing operations	$25,250	$22,908	'
Weighted Average Number of Shares Outstanding, Basic	146,425,000	118,688,000	'
Income from Continuing Operations, Per Basic Share	$0.17	$0.19	'
Dilutive units for long-term compensation plans	670,000	844,000	'
Weighted Average Number of Shares Outstanding, Diluted	147,095,000	119,532,000	'
Income from Continuing Operations, Per Diluted Share	$0.17	$0.19	'
Income from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	47,775	49,828	'
Income from Discontinued Operations, Net of Tax, Per Basic Share	$0.32	$0.41	'
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	$0.32	$0.41	'
Net Income (Loss) Available to Common Stockholders, Basic	71,900	71,239	'
Earnings Per Share, Basic	$0.49	$0.60	'
Earnings Per Share, Diluted	$0.49	$0.60	'
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,247,000	992,000	'
Stock Issued During Period, Shares, Stock Options Exercised	1,000	'	504,000
Liberty Property Limited Partnership [Member]	'	'	'
Income Per Common Unit [Line Items]	'	'	'
Income from continuing operations	25,978	24,828	'
Less: Preferred unit distributions	-118	-1,211	'
Income from Continuing Operations available to Common Unitholders	25,860	23,617	'
Weighted Average Number of Shares Outstanding, Basic	149,981,000	122,402,000	'
Income from Continuing Operations, Per Basic Share	$0.17	$0.19	'
Dilutive units for long-term compensation plans	670,000	844,000	'
Weighted Average Number of Shares Outstanding, Diluted	150,651,000	123,246,000	'
Income from Continuing Operations, Per Diluted Share	$0.17	$0.19	'
Income from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	47,775	49,828	'
Income from Discontinued Operations, Net of Tax, Per Basic Share	$0.32	$0.41	'
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	$0.32	$0.41	'
Net Income (Loss) Available to Common Stockholders, Basic	$73,635	$73,445	'
Earnings Per Share, Basic	$0.49	$0.60	'
Earnings Per Share, Diluted	$0.49	$0.60	'
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,247,000	992,000	'
Stock Issued During Period, Shares, Stock Options Exercised	1,000	'	504,000

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Cumulative Translation Adjustment Summary [Roll Forward]	'	'	'
Beginning balance	$8,592	$3,195	'
Translation adjustment	1,346	-4,851	'
Ending balance	9,938	-1,656	'
Cumulative Cash Flow Hedge Adjustment Summary [Roll Forward]	'	'	'
Beginning balance	1,584	0	'
Unrealized losses	-511	0	'
Ending balance	1,073	0	'
Total accumulated other comprehensive income	11,011	-1,656	'
Less: portion included in noncontrolling interest - operating partnership	-454	-149	'
Total accumulated other comprehensive income included in shareholders' equity	$10,557	($1,805)	$9,742

Segment_Information_Performanc

Segment Information - Performance of the Reportable Segments Based on Property Level Operating Income (Details) (USD $)	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Segment Reporting Information [Line Items]	'		'
Operating revenue	$197,615,000		$147,127,000
Net operating income	59,458,000		46,928,000
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'		'
Interest expense	-39,207,000		-27,739,000
Depreciation and amortization expense	-57,589,000		-45,585,000
Equity in earnings of unconsolidated joint ventures	4,159,000		1,757,000
General and administrative expense	-18,361,000		-19,793,000
Income taxes	-531,000		-491,000
Income from continuing operations	26,331,000		24,828,000
Intersegment Eliminations [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	0		0
Operating Segments [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	202,657,000		177,951,000
Net operating income	122,775,000		106,506,000
Operating Segments [Member] | Carolinas [Member] | North America [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	8,316,000		7,279,000
Net operating income	5,742,000		4,914,000
Operating Segments [Member] | Chicago Milwaukee [Member] | North America [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	8,570,000		2,693,000
Net operating income	5,163,000		2,174,000
Operating Segments [Member] | Houston [Member] | North America [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	11,867,000		8,334,000
Net operating income	7,053,000		5,250,000
Operating Segments [Member] | Lehigh Central PA [Member] | North America [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	29,623,000		24,677,000
Net operating income	19,240,000		16,668,000
Operating Segments [Member] | Minnesota [Member] | North America [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	13,750,000		15,383,000
Net operating income	6,619,000		7,712,000
Operating Segments [Member] | Orlando [Member] | North America [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	7,995,000		7,696,000
Net operating income	5,492,000		5,251,000
Operating Segments [Member] | Philadelphia [Member] | North America [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	9,408,000		8,333,000
Net operating income	6,721,000		5,879,000
Operating Segments [Member] | Richmond Hampton Roads [Member] | North America [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	10,068,000		10,146,000
Net operating income	5,920,000		6,226,000
Operating Segments [Member] | South Florida [Member] | North America [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	12,309,000		8,558,000
Net operating income	7,527,000		4,575,000
Operating Segments [Member] | Southeastern PA [Member] | North America [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	38,437,000		41,054,000
Net operating income	19,600,000		22,613,000
Operating Segments [Member] | Tampa [Member] | North America [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	13,173,000		12,963,000
Net operating income	8,441,000		8,254,000
Operating Segments [Member] | United Kingdom [Member] | European Union [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	4,102,000		1,100,000
Net operating income	3,526,000		-133,000
Operating Segments [Member] | Other Segments [Member] | North America [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	35,039,000		29,735,000
Net operating income	21,731,000		17,123,000
Discontinued Operations [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	-4,763,000		-31,080,000
Corporate, Non-Segment [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Operating revenue	-279,000		256,000
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'		'
Interest expense	-39,764,000	[1]	-32,082,000	[1]
Depreciation and amortization expense	-44,536,000	[2]	-29,307,000	[2]
Equity in earnings of unconsolidated joint ventures	4,159,000		1,757,000
General and administrative expense	-12,401,000	[2]	-13,877,000	[2]
Discontinued operations excluding gain on property dispositions	-1,658,000		-8,115,000
Income taxes	-483,000	[2]	-491,000	[2]
Other	($1,761,000)		$437,000
[1]	Includes interest on discontinued operations.
[2]	Excludes costs which are included in determining segment-level net operating income.

Segment_Information_Total_Asse

Segment Information - Total Assets by Segment (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]	'	'
Assets	$6,762,664,000	$6,775,560,000
Operating Segments [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	6,350,979,000	6,542,540,000
Corporate, Non-Segment [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	411,685,000	233,020,000
North America [Member] | Operating Segments [Member] | Carolinas [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	260,502,000	257,230,000
North America [Member] | Operating Segments [Member] | Chicago Milwaukee [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	411,677,000	413,585,000
North America [Member] | Operating Segments [Member] | Houston [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	389,279,000	380,248,000
North America [Member] | Operating Segments [Member] | Lehigh Central PA [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	952,396,000	938,824,000
North America [Member] | Operating Segments [Member] | Minnesota [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	339,772,000	335,613,000
North America [Member] | Operating Segments [Member] | Orlando [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	253,311,000	253,888,000
North America [Member] | Operating Segments [Member] | Philadelphia [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	323,098,000	316,810,000
North America [Member] | Operating Segments [Member] | Richmond Hampton Roads [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	248,580,000	250,008,000
North America [Member] | Operating Segments [Member] | South Florida [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	378,121,000	380,138,000
North America [Member] | Operating Segments [Member] | Southeastern PA [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	695,294,000	695,966,000
North America [Member] | Operating Segments [Member] | Tampa [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	335,984,000	337,300,000
North America [Member] | Operating Segments [Member] | Other Segments [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	1,501,146,000	1,735,393,000
European Union [Member] | Operating Segments [Member] | United Kingdom [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	$261,819,000	$247,537,000

Accounting_for_the_Impairment_2

Accounting for the Impairment or Disposal of Long-Lived Assets (Details) (USD $)

3 Months Ended

3 Months Ended

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Nov. 30, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Jan. 31, 2014

Jan. 31, 2014

Jan. 31, 2014

Jan. 31, 2014

Discontinued Operations [Member]

Discontinued Operations [Member]

Portfolio Sale, Total [Member]

Portfolio Sale, Total [Member]

Portfolio Sale, Total [Member]

Portfolio Sale, Total [Member]

Other Properties [Member]

Other Properties [Member]

Portfolio Sale, first settlement [Member]

Portfolio Sale, Second Settlement [Member]

Portfolio Sale, Second Settlement [Member]

Portfolio Sale, Second Settlement [Member]

Portfolio Sale, Second Settlement [Member]

properties

Discontinued Operations [Member]

Discontinued Operations [Member]

Discontinued Operations [Member]

Discontinued Operations [Member]

acre

Other Segments [Member]

Other Segments [Member]

Southeastern PA [Member]

sqft

properties

Maryland [Member]

New Jersey [Member]

sqft

sqft

properties

properties

properties

sqft

sqft

acre

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Real Estate Properties

'

'

'

'

'

97

'

'

'

'

49

'

23

24

1

Area of Real Estate Property

'

'

'

'

'

6,600,000

'

'

'

'

4,000,000

'

1,400,000

1,200,000

37,000

Significant Disposals, Sale Proceeds

'

'

'

'

'

$697,300,000

'

'

'

'

$367,700,000

$329,600,000

'

'

'

Number of Real Estate Settlements

'

'

'

'

2

'

'

'

'

'

'

'

'

'

'

Area of Land

'

'

'

'

'

'

'

'

'

'

140

'

19

'

'

Proceeds from Sale of Property, Plant, and Equipment

'

'

'

'

'

'

'

'

0

74,700,000

'

'

'

'

'

Discontinued Operation, Income (Loss) from Discontinued Operation Disclosures [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revenues

'

'

'

'

'

'

4,763,000

27,140,000

'

'

'

'

'

'

'

Operating expenses

'

'

'

'

'

'

-2,570,000

-9,433,000

'

'

'

'

'

'

'

Interest and other income

'

'

'

'

'

'

22,000

49,000

'

'

'

'

'

'

'

Interest expense

'

'

'

'

'

'

-557,000

-3,772,000

'

'

'

'

'

'

'

Depreciation and Amortization

'

'

'

'

'

'

0

-7,311,000

'

'

'

'

'

'

'

Income before gain on property dispositions

'

'

'

'

'

'

1,658,000

6,673,000

'

'

'

'

'

'

'

Gain on property dispositions

46,117,000

41,713,000

'

'

'

'

46,074,000

0

'

'

'

'

'

'

'

Income from discontinued operations

47,775,000

49,828,000

47,775,000

49,828,000

'

'

47,732,000

6,673,000

43,000

43,155,000

'

'

'

'

'

Noncontrolling Interest

'

'

'

'

'

'

-1,125,000

-200,000

'

'

'

'

'

'

'

Income from discontinued operations available to common shareholders

'

'

'

'

'

'

46,607,000

6,473,000

'

'

'

'

'

'

'

Discontinued Operation, Additional Disclosures [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Disposal Group, Including Discontinued Operation, Operating Cash Flows

'

'

-2,700,000

14,700,000

'

'

'

'

'

'

'

'

'

'

'

Disposal Group, Including Discontinued Operations, Investing Cash Flows

'

'

$313,100,000

($3,800,000)

'

'

'

'

'

'

'

'

'

'

'

Noncontrolling_Interests_Narra

Noncontrolling Interests - Narrative (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Millions, except Share data, unless otherwise specified
Stockholders' Equity Attributable to Noncontrolling Interest [Abstract]	'	'
Common units, units outstanding	3,553,566	3,556,556
Market value of common units based on closing price	$131.30	'

Limited_Partners_Equity_of_the1

Limited Partners' Equity of the Operating Partnership - Narrative (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Millions, except Share data, unless otherwise specified
Limited Partners' Capital Account [Line Items]	'	'
market value of the outstanding common units	$131.30	'
Liberty Property Limited Partnership [Member]	'	'
Limited Partners' Capital Account [Line Items]	'	'
Limited Partners' Capital Account, Units Outstanding	3,553,566	3,556,556
market value of the outstanding common units	$131.30	'

Noncontrolling_Interest_Operat2

Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units (Details) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Limited Partners' Capital Account - Preferred Units [Line Items]	'	'
Preferred Units, Outstanding	0	0
Series I 2 [Member]	'	'
Limited Partners' Capital Account - Preferred Units [Line Items]	'	'
Noncontrolling Interest in Operating Partnerships	$7,537	'
Preferred Units, Outstanding	301,483	301,483
Redeemable Preferred Units Liquidation Preference	$25	'
Preferred Stock Dividends Rate Percentage Or Per Dollar Amount	6.25%	'

Indebtedness_Details

Indebtedness (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014
			Line of Credit [Member]	Line of Credit [Member]	Total Debt to Total Assets Ratio [Member]	EBITDA to Fixed Charges Ratio [Member]	Unsecured Debt to Unencumbered Asset Ratio [Member]	Unencumbered Net Operating Income to Unsecured Interest Expense [Member]
			Old Credit Facility [Member]	New Credit Facility [Member]	Line of Credit [Member]	Line of Credit [Member]	Line of Credit [Member]	Line of Credit [Member]
					New Credit Facility [Member]		New Credit Facility [Member]	New Credit Facility [Member]
Debt Instrument [Line Items]	'	'	'	'	'	'	'	'
Debt Instrument, Basis Spread on Variable Rate	'	'	'	1.05%	'	'	'	'
Debt Instrument, Maturity Date	'	'	2-Nov-15	26-Mar-18	'	'	'	'
Line of Credit Facility, Competitive Bid Option, Percentage	'	'	'	50.00%	'	'	'	'
Line of Credit Facility, Maximum Borrowing Capacity	'	'	$500,000,000	$800,000,000	'	'	'	'
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	'	'	'	0.20%	'	'	'	'
Borrowed Funds	'	'	'	'	0.6	'	'	'
Assets	6,762,664,000	6,775,560,000	'	'	1	'	'	'
Line of Credit Facility, Covenant Terms, Earnings before Interest, Taxes, Depreciation and Amortization to Fixed Charges Ratio	'	'	'	'	'	$1.50	'	'
Line of Credit Facility, Unsecured Debt to Unencumbered Asset Value, Maximum	'	'	'	'	'	'	60.00%	'
Line of Credit Facility, Unencumbered Net Operating Income to Unsecured Interest Expense, Minimum	'	'	'	'	'	'	'	175.00%

Disclosure_of_Fair_Value_of_Fi2

Disclosure of Fair Value of Financial Instruments (Details) (Fair Value, Inputs, Level 3 [Member], USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Reported Value Measurement [Member] | Unsecured Debt [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Long-term Debt, Fair Value	$2,708,440	$2,708,213
Reported Value Measurement [Member] | Mortgage Loans on Real Estate [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Long-term Debt, Fair Value	542,809	545,306
Estimate of Fair Value Measurement [Member] | Unsecured Debt [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Long-term Debt, Fair Value	2,830,329	2,764,831
Estimate of Fair Value Measurement [Member] | Mortgage Loans on Real Estate [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Long-term Debt, Fair Value	$569,140	$573,944

Business_Combination_Details

Business Combination (Details) (Cabot Industrial Value Fund III [Member], USD $)	0 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Oct. 08, 2013	Dec. 31, 2013
	sqft
Business Acquisition [Line Items]	'	'
Business Acquisition, Effective Date of Acquisition	'	8-Oct-13
Business Acquisition, Name of Acquired Entity	'	'Cabot Industrial Fund III Operating Partnership, L.P.
Business Acquisition, Percentage of Voting Interests Acquired	100.00%	'
Area of Real Estate Property	23,000,000	'
Business Combination, Consideration Transferred	$1,469	'
Industrial Property [Member]	'	'
Business Acquisition [Line Items]	'	'
Number of Real Estate Properties	177	'
Mortgages [Member]	'	'
Business Acquisition [Line Items]	'	'
Business Combination, Consideration Transferred, Liabilities Incurred	$229.80	'

Derivative_Instruments_Details

Derivative Instruments (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Interest Rate Derivatives [Abstract]	'	'
Number of interest rate swap contracts	3	'
aggregate notional amount	$104,900,000	$105,200,000
Termination value of interest rate swap, including accrued interest	8,800,000	'
Interest Rate Cash Flow Hedges [Abstract]	'	'
Change in fair value of swaps as a decrease to other comprehensive income	871,000	'
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion	360,000	'
Ineffective portion of the change in the fair value of swaps as an adjustment to interest expense	18,000	'
Fair value of interest rate swaps	8,400,000	8,400,000
Amount estimated to be reclassified from accumulated other comprehensive income as an adjustment to interest expense	$1,400,000	'

Commitments_and_Contingencies_1

Commitments and Contingencies - Narrative (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Commitments And Contingencies [Line Items]	'	'	'
Operating ground lease expense	$47,000	$40,000	'
Loss Contingency, Pending Claims, Number	0	'	'
Letter of credit obligations	8,100,000	'	'
Development in Process	242,771,000	'	209,187,000
Construction in Progress [Member]	'	'	'
Commitments And Contingencies [Line Items]	'	'	'
Number of Real Estate Properties	15	'	'
Leasable space of buildings	4,900,000	'	'
Anticipated aggregate investment	406,100,000	'	'
Deferred Costs, Leasing, Gross	10,800,000	'	'
Development Not Yet Commenced [Member]	'	'	'
Commitments And Contingencies [Line Items]	'	'	'
Anticipated aggregate investment	12,700,000	'	'
Land and building improvements	12,800,000	'	'
Land Held for Development [Member]	'	'	'
Commitments And Contingencies [Line Items]	'	'	'
Purchase Commitment, Remaining Minimum Amount Committed	52,800,000	'	'
Maximum [Member]	'	'	'
Commitments And Contingencies [Line Items]	'	'	'
Potential payments for tenant allowances	$36,300,000	'	'

Commitments_and_Contingencies_2

Commitments and Contingencies - Future Minimum Rental Payments (Details) (USD $)	Mar. 31, 2014
In Thousands, unless otherwise specified
Commitments and Contingencies [Abstract]	'
2014	$274
2015	384
2016	403
2017	403
2018	403
2019 through 2034	5,575
Total	$7,442

Supplemental_Disclosure_to_Sta2

Supplemental Disclosure to Statements of Cash Flows (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Supplemental Cash Flow Information [Abstract]	'	'
Write off of fully depreciated property and deferred costs	$11,279	$7,182
Write off of depreciated property and deferred costs due to sale	131,026	23,906
Unrealized losses on cash flow hedge, non cash transaction	($511)	$0