Liberty Property Trust (LPT) 10-Q 30 Apr 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document	3 Months Ended
	Mar. 31, 2015	Apr. 28, 2015
Entity Information [Line Items]
Entity Registrant Name	LIBERTY PROPERTY TRUST
Entity Central Index Key	921112
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Amendment Flag	FALSE
Entity Common Stock, Shares Outstanding		149,471,760
Liberty Property Limited Partnership [Member]
Entity Information [Line Items]
Entity Registrant Name	LIBERTY PROPERTY LIMITED PARTNERSHIP
Entity Central Index Key	921113

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
ASSETS
Land and land improvements	$1,187,786	$1,189,760
Building and improvements	5,347,120	5,343,908
Less accumulated depreciation	-1,221,059	-1,182,569
Operating real estate	5,313,847	5,351,099
Development in progress	269,518	277,411
Land held for development	272,349	269,059
Net real estate	5,855,714	5,897,569
Cash and cash equivalents	38,755	69,346
Restricted cash	18,911	20,325
Accounts receivable	19,039	15,481
Deferred rent receivable	113,129	107,909
Deferred financing and leasing costs, net of accumulated amortization (2015, $173,076; 2014, $169,468)	202,231	206,286
Investments in and advances to unconsolidated joint ventures	215,403	208,832
Assets held for sale	0	8,389
Prepaid expenses and other assets	101,322	91,399
Total assets	6,564,504	6,625,536
LIABILITIES
Mortgage loans	484,584	487,301
Unsecured notes	2,607,874	2,509,094
Credit facility	50,000	167,000
Accounts payable	51,783	52,043
Accrued interest	36,691	24,513
Dividend and distributions payable	72,512	72,253
Other liabilities	199,311	219,418
Total liabilities	3,502,755	3,531,622
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of March 31, 2015 and December 31, 2014	7,537	7,537
EQUITY
Common shares of beneficial interest, $.001 par value, 283,987,000 shares authorized; 150,367,813 (includes 1,249,909 in treasury) and 149,807,179 (includes 1,249,909 in treasury) shares issued and outstanding as of March 31, 2015 and December 31, 2014, respectively	150	150
Additional paid-in capital	3,760,834	3,740,594
Accumulated other comprehensive loss	-17,346	-6,252
Distributions in excess of net income	-694,748	-654,869
Common shares in treasury, at cost, 1,249,909 shares as of March 31, 2015 and December 31, 2014	-51,951	-51,951
Total Liberty Property Trust shareholders' equity	2,996,939	3,027,672
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnerships	53,354	54,786
Noncontrolling interest - consolidated joint ventures	3,919	3,919
Total equity	3,054,212	3,086,377
Total liabilities, noncontrolling interest - operating partnership and equity	6,564,504	6,625,536
Liberty Property Limited Partnership [Member]
ASSETS
Land and land improvements	1,187,786	1,189,760
Building and improvements	5,347,120	5,343,908
Less accumulated depreciation	-1,221,059	-1,182,569
Operating real estate	5,313,847	5,351,099
Development in progress	269,518	277,411
Land held for development	272,349	269,059
Net real estate	5,855,714	5,897,569
Cash and cash equivalents	38,755	69,346
Restricted cash	18,911	20,325
Accounts receivable	19,039	15,481
Deferred rent receivable	113,129	107,909
Deferred financing and leasing costs, net of accumulated amortization (2015, $173,076; 2014, $169,468)	202,231	206,286
Investments in and advances to unconsolidated joint ventures	215,403	208,832
Assets held for sale	0	8,389
Prepaid expenses and other assets	101,322	91,399
Total assets	6,564,504	6,625,536
LIABILITIES
Mortgage loans	484,584	487,301
Unsecured notes	2,607,874	2,509,094
Credit facility	50,000	167,000
Accounts payable	51,783	52,043
Accrued interest	36,691	24,513
Dividend and distributions payable	72,512	72,253
Other liabilities	199,311	219,418
Total liabilities	3,502,755	3,531,622
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of March 31, 2015 and December 31, 2014	7,537	7,537
EQUITY
General partner’s equity - 149,117,904 (net of 1,249,909 treasury units) and 148,557,270 (net of 1,249,909 treasury units) common units outstanding as of March 31, 2015 and December 31, 2014, respectively	2,996,939	3,027,672
Limited partners' equity	53,354	54,786
Noncontrolling interest - operating partnership
Noncontrolling interest - consolidated joint ventures	3,919	3,919
Total equity	3,054,212	3,086,377
Total liabilities, noncontrolling interest - operating partnership and equity	$6,564,504	$6,625,536

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parentheticals) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Amortized Cost on Deferred Financing and Leasing Costs	$173,076,000	$169,468,000
Noncontrolling Interest Operating Partnership Common Units Outstanding	3,539,075	3,553,566
Common Stock, Par or Stated Value Per Share	$0.00	$0.00
Common Stock, Shares Authorized	283,987,000	283,987,000
Common Stock, Shares, Issued	150,367,813	149,807,179
Common Stock, Shares, Outstanding	150,367,813	149,807,179
Treasury Stock, Shares	1,249,909	1,249,909
Liberty Property Limited Partnership [Member]
Amortized Cost on Deferred Financing and Leasing Costs	$173,076,000	$169,468,000
Limited Partners' Capital Account, Units Outstanding	3,539,075	3,553,566
Common Stock, Shares, Outstanding	149,117,904	148,557,270
Treasury Stock, Shares	1,249,909	1,249,909
Series I 2 [Member]
Temporary Equity, Shares Outstanding	301,483	301,483
Series I 2 [Member] | Liberty Property Limited Partnership [Member]
Temporary Equity, Shares Outstanding	301,483	301,483

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended
Share data in Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
OPERATING REVENUE
Rental	$148,585,000	$138,949,000
Operating expense reimbursement	58,316,000	58,681,000
Total operating revenue	206,901,000	197,630,000
OPERATING EXPENSE
Rental property	35,571,000	38,641,000
Real estate taxes	26,164,000	24,501,000
General and administrative	18,802,000	18,356,000
Depreciation and amortization	58,796,000	56,734,000
Impairment - real estate assets	15,739,000	0
Total operating expenses	155,072,000	138,232,000
Operating income	51,829,000	59,398,000
OTHER INCOME (EXPENSE)
Other income	6,371,000	2,439,000
Interest expense	-34,670,000	-39,207,000
Total other income (expense)	-28,299,000	-36,768,000
Income before gain on property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	23,530,000	22,630,000
Gain on property dispositions	2,271,000	0
Income taxes	-845,000	-531,000
Equity in earnings of unconsolidated joint ventures	6,906,000	4,159,000
Income from continuing operations	31,862,000	26,258,000
Discontinued operations (including net gain on property dispositions of $46,115 for the three months ended March 31, 2014)	0	47,848,000
Net income	31,862,000	74,106,000
Noncontrolling interest – operating partnership	-853,000	-1,853,000
Noncontrolling interest - consolidated joint ventures	-58,000	-353,000
Net income available to common shareholders	30,951,000	71,900,000
Comprehensive income attributable to common shareholders
Net income	31,862,000	74,106,000
Other comprehensive (loss) income - foreign currency translation	-10,410,000	1,346,000
Other comprehensive loss - derivative instruments	-947,000	-511,000
Other comprehensive (loss) income	-11,357,000	835,000
Total comprehensive income	20,505,000	74,941,000
Less: comprehensive income attributable to noncontrolling interest	-648,000	-2,226,000
Comprehensive income attributable to common shareholders	19,857,000	72,715,000
Weighted average number of common shares outstanding
Basic	148,315	146,425
Diluted	149,031	147,095
Amounts attributable to common shareholders
Income from continuing operations	30,951,000	25,179,000
Discontinued operations	0	46,721,000
Net income available to common shareholders	30,951,000	71,900,000
Liberty Property Limited Partnership [Member]
OPERATING REVENUE
Rental	148,585,000	138,949,000
Operating expense reimbursement	58,316,000	58,681,000
Total operating revenue	206,901,000	197,630,000
OPERATING EXPENSE
Rental property	35,571,000	38,641,000
Real estate taxes	26,164,000	24,501,000
General and administrative	18,802,000	18,356,000
Depreciation and amortization	58,796,000	56,734,000
Impairment - real estate assets	15,739,000	0
Total operating expenses	155,072,000	138,232,000
Operating income	51,829,000	59,398,000
OTHER INCOME (EXPENSE)
Other income	6,371,000	2,439,000
Interest expense	-34,670,000	-39,207,000
Total other income (expense)	-28,299,000	-36,768,000
Income before gain on property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	23,530,000	22,630,000
Gain on property dispositions	2,271,000	0
Income taxes	-845,000	-531,000
Equity in earnings of unconsolidated joint ventures	6,906,000	4,159,000
Income from continuing operations	31,862,000	26,258,000
Discontinued operations (including net gain on property dispositions of $46,115 for the three months ended March 31, 2014)	0	47,848,000
Net income	31,862,000	74,106,000
Noncontrolling interest - consolidated joint ventures	-58,000	-353,000
Preferred unit distributions	-118,000	-118,000
Net income available to common shareholders	31,686,000	73,635,000
Comprehensive income attributable to common shareholders
Net income	31,862,000	74,106,000
Other comprehensive (loss) income - foreign currency translation	-10,410,000	1,346,000
Other comprehensive loss - derivative instruments	-947,000	-511,000
Other comprehensive (loss) income	-11,357,000	835,000
Total comprehensive income	20,505,000	74,941,000
Weighted average number of common shares outstanding
Basic	151,856	149,981
Diluted	152,572	150,651
Net income allocated to general partners	30,951,000	71,900,000
Net income allocated to limited partners	853,000	1,853,000
Amounts attributable to common shareholders
Income from continuing operations	31,804,000	25,905,000
Net income available to common shareholders	$31,686,000	$73,635,000
Common shares [Member]
Basic:
Income from continuing operations	$0.21	$0.17
Income from discontinued operations	$0	$0.32
Income per common share - basic	$0.21	$0.49
Diluted:
Income from continuing operations	$0.21	$0.17
Income from discontinued operations	$0	$0.32
Income per common share - diluted	$0.21	$0.49
Distributions per common share or unit	$0.48	$0.48
Common Units [Member] | Liberty Property Limited Partnership [Member]
Basic:
Income from continuing operations	$0.21	$0.17
Income from discontinued operations	$0	$0.32
Income per common share - basic	$0.21	$0.49
Diluted:
Income from continuing operations	$0.21	$0.17
Income from discontinued operations	$0	$0.32
Income per common share - diluted	$0.21	$0.49
Distributions per common share or unit	$0.48	$0.48

Income_Statement_Parenthetical

Income Statement Parenthetical (Parentheticals) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Gain on property dispositions	$0	$46,115
Liberty Property Limited Partnership [Member]
Gain on property dispositions	$0	$46,115

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-consolidated joint ventures [Member]	Total Equity [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-consolidated joint ventures [Member]	Total Equity [Member]
Noncontrolling Interest - Operating Partnership (Mezzanine) - Beginning Balance at Dec. 31, 2014	$7,537,000										$7,537,000
Beginning Balance at Dec. 31, 2014	3,086,377,000	150,000	3,740,594,000	-6,252,000	-654,869,000	-51,951,000	3,027,672,000	54,786,000	3,919,000	3,086,377,000	3,086,377,000	3,027,672,000	54,786,000	3,919,000	3,086,377,000
Net proceeds from the issuance of common shares		0	12,579,000				12,579,000			12,579,000
Net income	31,862,000				30,951,000		30,951,000	735,000	58,000	31,744,000	31,862,000	30,951,000	735,000	58,000	31,744,000
Net income (Mezzanine)	118,000										118,000
Distributions (Mezzanine)	-118,000										-118,000
Redemption of limited partners common units for common shares												224,000	-224,000		0
Contributions from partners												20,016,000			20,016,000
Distributions					-70,830,000		-70,830,000	-1,680,000	-58,000	-72,568,000
Distributions to partners												-70,830,000	-1,680,000	-58,000	-72,568,000
Share-based compensation			7,437,000				7,437,000			7,437,000
Other comprehensive loss - foreign currency translation	-10,410,000			-10,169,000			-10,169,000	-241,000		-10,410,000	-10,410,000	-10,169,000	-241,000		-10,410,000
Other comprehensive loss - derivative instruments	-947,000			-925,000			-925,000	-22,000		-947,000	-947,000	-925,000	-22,000		-947,000
Redemption of noncontrolling interests - common units			224,000				224,000	-224,000		0
Noncontrolling Interest - Operating Partnership (Mezzanine) - Ending Balance at Mar. 31, 2015	7,537,000										7,537,000
Ending Balance at Mar. 31, 2015	$3,054,212,000	$150,000	$3,760,834,000	($17,346,000)	($694,748,000)	($51,951,000)	$2,996,939,000	$53,354,000	$3,919,000	$3,054,212,000	$3,054,212,000	$2,996,939,000	$53,354,000	$3,919,000	$3,054,212,000

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
OPERATING ACTIVITIES
Net income	$31,862	$74,106
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	59,431	57,589
Amortization of deferred financing costs	1,073	1,510
Impairment - real estate assets	15,739	0
Equity in earnings of unconsolidated joint ventures	-6,906	-4,159
Gain on property dispositions	-2,271	-46,117
Share-based compensation/Non-cash compensation	7,437	6,580
Other	-2,990	-635
Changes in operating assets and liabilities:
Restricted cash	489	31,726
Accounts receivable	-3,670	-4,052
Deferred rent receivable	-5,504	-2,765
Prepaid expenses and other assets	-13,058	-26,557
Accounts payable	-116	6,562
Accrued interest	12,178	16,441
Other liabilities	-3,718	-36,537
Net cash provided by operating activities	89,976	73,692
INVESTING ACTIVITIES
Investment in operating properties - acquisitions	0	-37,635
Investment in operating properties - other	-12,805	-16,522
Investments in and advances to unconsolidated joint ventures	-5,822	-429
Distributions from unconsolidated joint ventures	6,098	2,978
Net proceeds from disposition of properties/land	40,998	327,160
Net (advances on) proceeds from public reimbursement receivable/escrow	-1,601	5,001
Investment in development in progress	-48,001	-74,478
Investment in land held for development	-4,045	-1,967
Investment in deferred leasing costs	-9,684	-9,158
Net cash (used in) provided by investing activities	-34,862	194,950
FINANCING ACTIVITIES
Net proceeds from issuance of common shares	12,579	15,472
Proceeds from unsecured notes	398,576	0
Repayment of unsecured notes	-300,000	0
Repayments of mortgage loans	-2,160	-2,019
Proceeds from credit facility	390,000	0
Repayments on credit facility	-507,000	0
Payment of deferred financing costs	-3,551	-3,619
Distribution paid on common shares	-70,562	-69,634
Distribution paid on units	-1,863	-1,914
Net cash used in financing activities	-83,981	-61,714
Net (decrease) increase in cash and cash equivalents	-28,867	206,928
(Decrease) increase in cash and cash equivalents related to foreign currency translation	-1,724	211
Cash and cash equivalents at beginning of period	69,346	163,414
Cash and cash equivalents at end of period	38,755	370,553
Liberty Property Limited Partnership [Member]
OPERATING ACTIVITIES
Net income	31,862	74,106
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	59,431	57,589
Amortization of deferred financing costs	1,073	1,510
Impairment - real estate assets	15,739	0
Equity in earnings of unconsolidated joint ventures	-6,906	-4,159
Gain on property dispositions	-2,271	-46,117
Share-based compensation/Non-cash compensation	7,437	6,580
Other	-2,990	-635
Changes in operating assets and liabilities:
Restricted cash	489	31,726
Accounts receivable	-3,670	-4,052
Deferred rent receivable	-5,504	-2,765
Prepaid expenses and other assets	-13,058	-26,557
Accounts payable	-116	6,562
Accrued interest	12,178	16,441
Other liabilities	-3,718	-36,537
Net cash provided by operating activities	89,976	73,692
INVESTING ACTIVITIES
Investment in operating properties - acquisitions	0	-37,635
Investment in operating properties - other	-12,805	-16,522
Investments in and advances to unconsolidated joint ventures	-5,822	-429
Distributions from unconsolidated joint ventures	6,098	2,978
Net proceeds from disposition of properties/land	40,998	327,160
Net (advances on) proceeds from public reimbursement receivable/escrow	-1,601	5,001
Investment in development in progress	-48,001	-74,478
Investment in land held for development	-4,045	-1,967
Investment in deferred leasing costs	-9,684	-9,158
Net cash (used in) provided by investing activities	-34,862	194,950
FINANCING ACTIVITIES
Proceeds from unsecured notes	398,576	0
Repayment of unsecured notes	-300,000	0
Repayments of mortgage loans	-2,160	-2,019
Proceeds from credit facility	390,000	0
Repayments on credit facility	-507,000	0
Payment of deferred financing costs	-3,551	-3,619
Capital contributions	12,579	15,472
Distributions to partners	-72,425	-71,548
Net cash used in financing activities	-83,981	-61,714
Net (decrease) increase in cash and cash equivalents	-28,867	206,928
(Decrease) increase in cash and cash equivalents related to foreign currency translation	-1,724	211
Cash and cash equivalents at beginning of period	69,346	163,414
Cash and cash equivalents at end of period	$38,755	$370,553

Organization_and_Basis_of_Pres

Organization and Basis of Presentation	3 Months Ended
	Mar. 31, 2015
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 97.7% of the common equity of the Operating Partnership at March 31, 2015. The Company owns and operates industrial properties nationally and owns and operates office properties in a focused group of office markets. 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, 2014. 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.
	Recently Issued Accounting Standards
	In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09"), which supersedes nearly all existing revenue recognition guidance. The standard clarifies the required factors that an entity must consider when recognizing revenue. The standard also requires additional disclosures concerning contracts with customers, judgments concerning revenue recognition, and assets recognized for the costs to obtain or fulfill a contract. ASU 2014-09 is effective for the Company beginning January 1, 2017. The Company is evaluating the impact ASU 2014-09 will have on its financial position and results of operations.
	In April 2015, the FASB issued ASU 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs. The standard requires the costs for issuing debt to appear on a balance sheet as a direct deduction from the debt's value. ASU 2015-03 is effective for the Company beginning January 1, 2016. The standard would be applied retrospectively. The Company does not anticipate that the adoption of ASU 2015-03 will have a material impact on its financial position or results of operations.

Income_per_Common_Share_of_the

Income per Common Share of the Trust	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [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, 2015					March 31, 2014
		Income		Weighted	Per Share		Income		Weighted	Per Share
		(Numerator)		Average			(Numerator)		Average
				Shares					Shares
				(Denominator)					(Denominator)
	Basic income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	30,951	148,315	$	0.21	$	25,179	146,425	$	0.17
	Dilutive shares for long-term compensation plans	—		716			—		670
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	30,951	149,031	$	0.21	$	25,179	147,095	$	0.17
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	—	148,315	$	—	$	46,721	146,425	$	0.32
	Dilutive shares for long-term compensation plans	—		716			—		670
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	—	149,031	$	—	$	46,721	147,095	$	0.32
	Basic income per common share
	Net income available to common shareholders	$	30,951	148,315	$	0.21	$	71,900	146,425	$	0.49
	Dilutive shares for long-term compensation plans	—		716			—		670
	Diluted income per common share
	Net income available to common shareholders	$	30,951	149,031	$	0.21	$	71,900	147,095	$	0.49
	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, 2015 was 596,000 as compared to 1,247,000 for the same period in 2014.
Stock Option Exercises [Text Block]	During the three months ended March 31, 2015, 44,000 common shares were issued upon the exercise of options. During the year ended December 31, 2014, 44,000 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, 2015
Earnings Per Share, Basic and Diluted [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, 2015						March 31, 2014
		Income			Weighted	Per Share		Income			Weighted	Per Share
		(Numerator)			Average			(Numerator)			Average
					Shares						Shares
					(Denominator)						(Denominator)
	Basic income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	30,951		148,315	$	0.21	$	25,179		146,425	$	0.17
	Dilutive shares for long-term compensation plans	—			716			—			670
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	30,951		149,031	$	0.21	$	25,179		147,095	$	0.17
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	—		148,315	$	—	$	46,721		146,425	$	0.32
	Dilutive shares for long-term compensation plans	—			716			—			670
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	—		149,031	$	—	$	46,721		147,095	$	0.32
	Basic income per common share
	Net income available to common shareholders	$	30,951		148,315	$	0.21	$	71,900		146,425	$	0.49
	Dilutive shares for long-term compensation plans	—			716			—			670
	Diluted income per common share
	Net income available to common shareholders	$	30,951		149,031	$	0.21	$	71,900		147,095	$	0.49
	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, 2015 was 596,000 as compared to 1,247,000 for the same period in 2014.
Stock Option Exercises [Text Block]	During the three months ended March 31, 2015, 44,000 common shares were issued upon the exercise of options. During the year ended December 31, 2014, 44,000 common shares were issued upon the exercise of options.
Liberty Property Limited Partnership [Member]
Earnings Per Share, Basic and Diluted [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, 2015						March 31, 2014
		Income (Numerator)			Weighted	Per Unit		Income			Weighted	Per Unit
					Average Units			(Numerator)			Average Units
					(Denominator)						(Denominator)
	Income from continuing operations - net of noncontrolling interest - consolidated joint ventures	$	31,804					$	25,905
	Less: Preferred unit distributions	(118		)				(118		)
	Basic income from continuing operations
	Income from continuing operations available to common unitholders	$	31,686		151,856	$	0.21	$	25,787		149,981	$	0.17
	Dilutive units for long-term compensation plans	—			716			—			670
	Diluted income from continuing operations
	Income from continuing operations available to common unitholders	$	31,686		152,572	$	0.21	$	25,787		150,651	$	0.17
	Basic income from discontinued operations
	Discontinued operations	$	—		151,856	$	—	$	47,848		149,981	$	0.32
	Dilutive units for long-term compensation plans	—			716			—			670
	Diluted income from discontinued operations
	Discontinued operations	$	—		152,572	$	—	$	47,848		150,651	$	0.32
	Basic income per common unit
	Income available to common unitholders	$	31,686		151,856	$	0.21	$	73,635		149,981	$	0.49
	Dilutive units for long-term compensation plans	—			716			—			670
	Diluted income per common unit
	Income available to common unitholders	$	31,686		152,572	$	0.21	$	73,635		150,651	$	0.49
	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, 2015 was 596,000 as compared to 1,247,000 for the same period in 2014.
Stock Option Exercises [Text Block]	During the three months ended March 31, 2015, 44,000 common units were issued upon exercise of options. During the year ended December 31, 2014, 44,000 common units were issued upon the exercise of options.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income	3 Months Ended
	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss) Note [Text Block]	Accumulated Other Comprehensive Loss
	The following table sets forth the components of Accumulated Other Comprehensive Loss (in thousands):
			Three Months Ended March 31,
			2015			2014
	Foreign Currency Translation:
	Beginning balance		$	(5,823	)	$	8,592
	Translation adjustment		(10,410		)	1,346
	Ending balance		(16,233		)	9,938
	Derivative Instruments:
	Beginning balance		(377		)	1,584
	Unrealized loss		(1,299		)	(871		)
	Reclassification adjustment (1)		352			360
	Ending balance		(1,324		)	1,073
	Total accumulated other comprehensive (loss) income		(17,557		)	11,011
	Less: portion included in noncontrolling interest – operating partnership		211			(454		)
	Total accumulated other comprehensive (loss) income included in shareholders' equity/owners' equity		$	(17,346	)	$	10,557
	-1	Amounts reclassified out of Accumulated Other Comprehensive (Loss) Income/General & Limited Partner's Equity into contractual interest expense.

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2015
Segment Reporting, Measurement Disclosures [Abstract]
Segment Information	Segment Information
	The Company owns and operates industrial properties nationally and owns and operates office properties in a focused group of office markets. 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; 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,
			2015			2014
	Operating revenue
		Carolinas	$	9,844		$	8,316
		Chicago/Milwaukee	9,793			8,570
		Houston	12,324			11,867
		Lehigh/Central PA	33,554			29,623
		Minnesota	12,672			13,750
		Orlando	5,264			7,995
		Philadelphia	9,982			9,408
		Richmond/Hampton Roads	10,490			10,068
		South Florida	12,206			12,309
		Southeastern PA	39,238			38,437
		Tampa	13,462			13,173
		United Kingdom	3,725			4,102
		Other	34,398			35,039
	Segment-level operating revenue		206,952			202,657
	Reconciliation to total operating revenues
		Discontinued operations	—			(4,748		)
		Other	(51		)	(279		)
	Total operating revenue		$	206,901		$	197,630
	Net operating income
		Carolinas	$	6,617		$	5,742
		Chicago/Milwaukee	6,743			5,163
		Houston	7,221			7,053
		Lehigh/Central PA	22,971			19,240
		Minnesota	5,985			6,619
		Orlando	3,571			5,492
		Philadelphia	7,022			6,721
		Richmond/Hampton Roads	6,229			5,920
		South Florida	6,829			7,527
		Southeastern PA	20,988			19,600
		Tampa	8,702			8,441
		United Kingdom	2,516			2,850
		Other	22,176			21,731
	Segment-level net operating income		127,570			122,099
	Reconciliation to income from continuing operations
		Interest expense (1)	(34,670		)	(39,764		)
		Depreciation/amortization expense (1) (2)	(43,514		)	(44,536		)
		Impairment - real estate assets	(15,739		)	—
		Gain on property dispositions	2,271			—
		Equity in earnings of unconsolidated joint ventures	6,906			4,159
		General and administrative expense (1) (2)	(12,574		)	(12,401		)
		Discontinued operations excluding interest and gain on property dispositions	—			(2,290		)
		Income taxes (2)	(707		)	(483		)
	Other	2,319			(526		)
Income from continuing operations		$	31,862		$	26,258
-1	Includes activity on discontinued operations.
-2	Excludes costs which are included in determining segment-level net operating income.
During the three months ended March 31, 2015, the Company did not acquire any operating properties.
During the three months ended March 31, 2015, the Company realized proceeds of $42.2 million from the sale of seven properties in the Company's Southeastern PA segment and segments grouped into the Company's "Other" category.

Accounting_for_the_Impairment_

Accounting for the Impairment or Disposal of Long-Lived Assets	3 Months Ended
	Mar. 31, 2015
Disposal Group, Including Discontinued Operation, Long Lived Assets [Abstract]
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	Accounting for the Impairment or Disposal of Long-Lived Assets
	Prior to the adoption of 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") on January 1, 2014, 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.
	A summary of the results of operations for the properties classified as discontinued operations through the respective disposition dates is as follows (in thousands):
		Three Months Ended March 31,
		2015		2014
	Revenues	$	—	$	4,748
	Operating expenses	—		(2,495		)
	Interest and other income	—		37
	Interest expense	—		(557		)
	Depreciation and amortization	—		—
	Income before gain on property dispositions	—		1,733
	Gain on property dispositions	—		46,115
	Net income	$	—	$	47,848
	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.
Asset Impairment Charges [Text Block]	Asset Impairment
	The Company anticipates the potential disposition of certain properties prior to the end of their remaining useful lives. During the three months ended March 31, 2015, the Company recognized $15.7 million in impairments, $13.4 million of which related to the Company's Richmond/Hampton Roads reportable segment and $2.3 million of which related to the Company's Southeastern Pennsylvania reportable segment. The Company determined these impairments based on third party offer prices and quoted offer prices for comparable transactions which are Level 2 and Level 3 inputs, respectively, according to the fair value hierarchy established by the FASB in Topic 820, "Fair Value Measurements and Disclosures." However, these properties are not classified as held for sale as all of the criteria for such classification have not been met as of March 31, 2015. The Company has evaluated each of its properties and land held for development and has determined that there were no additional valuation adjustments necessary at March 31, 2015.  There were no impairments recognized during the three months ended March 31, 2014.

Noncontrolling_Interests_of_th

Noncontrolling Interests of the Trust	3 Months Ended
	Mar. 31, 2015
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, 2015 have the same economic characteristics as common shares of the Trust. The 3,539,075 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 of unregistered common shares of the Trust. The market value of the 3,539,075 outstanding common units based on the closing price of the common shares of the Trust at March 31, 2015 was $126.3 million.

Limited_Partners_Equity_of_the

Limited Partners' Equity of the Operating Partnership	3 Months Ended
	Mar. 31, 2015
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, 2015 have the same economic characteristics as common shares of the Trust. The 3,539,075 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 of unregistered common shares of the Trust. The market value of the 3,539,075 outstanding common units based on the closing price of the common shares of the Trust at March 31, 2015 was $126.3 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, 2015 have the same economic characteristics as common shares of the Trust. The 3,539,075 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. 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 of unregistered common shares of the Trust. The market value of the 3,539,075 outstanding common units at March 31, 2015 based on the closing price of the common shares of the Trust at March 31, 2015 was $126.3 million.

Noncontrolling_Interest_Operat

Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units	3 Months Ended
	Mar. 31, 2015
Temporary Equity [Line Items]
Stockholders' Equity Note Disclosure [Text Block]	Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units
	As of March 31, 2015, the Company had outstanding the following cumulative preferred units of the Operating Partnership:
	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, 2015
Debt Disclosure [Abstract]
Debt Disclosure [Text Block]	Indebtedness
	In March 2015, the Company used proceeds from its unsecured credit facility together with available cash on hand to repay all $300 million of its 5.125% senior unsecured notes due March 2015.
	In March 2015, the Company issued $400 million of 3.75% senior unsecured notes due 2025. The net proceeds from this issuance were used to repay borrowings under the Company's unsecured credit facility and for general corporate purposes.

Disclosure_of_Fair_Value_of_Fi

Disclosure of Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2015
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, 2015 and December 31, 2014. 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 carrying value of the outstanding amounts under the Company's credit facility is a reasonable estimate of fair value because interest rates float at a rate based on LIBOR.
	The Company determines the fair value of its interest rate swaps by using the standard methodology of netting discounted future fixed cash payments with the discounted expected variable cash receipts. These variable cash receipts of interest rate swaps are based on expectations of future LIBOR interest rates (forward curves) estimated by observing market LIBOR interest rate curves. This is a Level 2 fair value calculation. Also, credit valuation adjustments are factored into the fair value calculations to account for potential nonperformance risk. These credit valuation adjustments were concluded to be not significant inputs for the fair value calculations for the periods presented. See Note 12 - Derivative Instruments.
	The Company used a discounted cash flow model to determine the estimated fair value of its debt as of March 31, 2015.  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, 2014 and March 31, 2015 (in thousands):
		Mortgage Loans				Unsecured Notes
		Carrying Value		Fair Value		Carrying Value		Fair Value
	As of December 31, 2014	$	487,301	$	501,231	$	2,509,094	$	2,704,069
	As of March 31, 2015	$	484,584	$	496,873	$	2,607,874	$	2,769,146

Derivative_Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Interest rate swaps [Text Block]	Derivative Instruments
	The Company borrows funds at a combination of fixed and variable rates. Borrowings under the Company's 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 loss (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.
	The Company determines the fair value of its interest rate swaps by using the standard methodology of netting discounted future fixed cash payments with the discounted expected variable cash receipts. These variable cash receipts of interest rate swaps are based on expectations of future LIBOR interest rates (forward curves) estimated by observing market LIBOR interest rate curves. This is a Level 2 fair value calculation. Also, credit valuation adjustments are factored into the fair value calculations to account for potential nonperformance risk. These credit valuation adjustments were concluded to be not significant inputs for the fair value calculations for the periods presented.
	The Company holds 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. The Swaps had aggregate notional amounts of $103.2 million and $103.6 million at March 31, 2015 and December 31, 2014, respectively, and expire at various dates between 2018 and 2020.
	For the three months ended March 31, 2015 and March 31, 2014, the effective portion of the change in the fair value of the swaps were decreases in the amount of $1.3 million and $871,000, respectively, which were recorded as decreases in other comprehensive income. These amounts reported in accumulated other comprehensive income will be reclassified to interest expense as interest payments are made on the variable rate mortgages. The amount of loss reclassified from accumulated other comprehensive income was $352,000 and $360,000 for the three months ended March 31, 2015 and March 31, 2014, respectively. The ineffective portion of the change in the fair value of the Swaps for the three months ended March 31, 2015 and March 31, 2014 in the amounts of $59,000 and $18,000, respectively, were recorded as increases to interest expense in the accompanying consolidated statements of comprehensive income.
	The fair value of the Swaps in the amounts of $9.0 million and $8.5 million as of March 31, 2015 and December 31, 2014, respectively, is included in other liabilities in the accompanying consolidated balance sheets. The Company estimates that $1.2 million will be reclassified from accumulated other comprehensive income as an increase to interest expense over the next 12 months.
	The Company has agreements with its derivative counterparties that contain a provision whereby if the Company defaults on any of its indebtedness, including defaults 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 $9.1 million.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [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, 2015, were as follows (in thousands):
	Year	Amount
	2015	$	507
	2016	686
	2017	686
	2018	686
	2019	686
	2020 through 2034	6,604
	Total	$	9,855
	Operating ground lease expense for the three months ended March 31, 2015 was $64,000 as compared to $47,000 for the same period in 2014.
	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, 2015 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.
	Comcast Innovation and Technology Center
	The Company has entered into two joint ventures for the purpose of developing and owning the Comcast Innovation & Technology Center (the "Project") located on the 1800 block of Arch Street in Philadelphia, Pennsylvania. The 59-story building will include 1.3 million square feet of rentable office space and a 222-room Four Seasons Hotel.  Completion of the first phase of the Project is anticipated to be in the third quarter of 2017. Project costs for the development of the Project, exclusive of tenant-funded interior improvements, are anticipated to be approximately $932 million.  The Company's investment in the Project is expected to be approximately $185 million with 20% ownership interests in both joint ventures.
	The two joint ventures have engaged the Company as the developer of the Project pursuant to a Development Agreement by which the Company agrees, in consideration for a development fee, to be responsible for all aspects of the development of the Project and to guarantee the timely lien-free completion of construction of the Project and the payment, subject to certain exceptions, of any cost overruns incurred in the development of the Project.
	Other
	As of March 31, 2015, the Company had letter of credit obligations of $4.2 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, 2015, the Company had 21 buildings under development. These buildings are expected to contain, when completed, a total of 3.8 million square feet of leasable space and represent an anticipated aggregate investment of $412.9 million. At March 31, 2015, development in progress totaled $269.5 million. In addition, as of March 31, 2015, the Company had invested $8.0 million in deferred leasing costs related to these development buildings. In addition, the Company had signed commitments for build-to-suit developments not yet commenced for an anticipated aggregate investment of $167.0 million.
	As of March 31, 2015, the Company was committed to $14.8 million in improvements on certain buildings and land parcels.
	As of March 31, 2015, the Company was committed to $51.0 million in future land purchases.
	As of March 31, 2015, the Company was obligated to pay for tenant improvements not yet completed for a maximum of $41.5 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, 2015
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, 2015 and 2014 (amounts in thousands):
		2015			2014
	Write-off of fully depreciated/amortized property and deferred costs	$	14,436		$	11,279
	Write-off of depreciated/amortized property and deferred costs due to sale	$	10,295		$	131,026
	Unrealized loss on cash flow hedge	$	(947	)	$	(511	)
	Changes in accrued development capital expenditures	$	(8,343	)	$	2,280
	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, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Issued Accounting Standards
	In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09"), which supersedes nearly all existing revenue recognition guidance. The standard clarifies the required factors that an entity must consider when recognizing revenue. The standard also requires additional disclosures concerning contracts with customers, judgments concerning revenue recognition, and assets recognized for the costs to obtain or fulfill a contract. ASU 2014-09 is effective for the Company beginning January 1, 2017. The Company is evaluating the impact ASU 2014-09 will have on its financial position and results of operations.
	In April 2015, the FASB issued ASU 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs. The standard requires the costs for issuing debt to appear on a balance sheet as a direct deduction from the debt's value. ASU 2015-03 is effective for the Company beginning January 1, 2016. The standard would be applied retrospectively. The Company does not anticipate that the adoption of ASU 2015-03 will have a material impact on its financial position or results of operations.

Income_per_Common_Share_of_the1

Income per Common Share of the Trust (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [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, 2015					March 31, 2014
		Income		Weighted	Per Share		Income		Weighted	Per Share
		(Numerator)		Average			(Numerator)		Average
				Shares					Shares
				(Denominator)					(Denominator)
	Basic income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	30,951	148,315	$	0.21	$	25,179	146,425	$	0.17
	Dilutive shares for long-term compensation plans	—		716			—		670
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	30,951	149,031	$	0.21	$	25,179	147,095	$	0.17
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	—	148,315	$	—	$	46,721	146,425	$	0.32
	Dilutive shares for long-term compensation plans	—		716			—		670
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	—	149,031	$	—	$	46,721	147,095	$	0.32
	Basic income per common share
	Net income available to common shareholders	$	30,951	148,315	$	0.21	$	71,900	146,425	$	0.49
	Dilutive shares for long-term compensation plans	—		716			—		670
	Diluted income per common share
	Net income available to common shareholders	$	30,951	149,031	$	0.21	$	71,900	147,095	$	0.49

Income_per_Common_Unit_of_the_1

Income per Common Unit of the Operating Partnership (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share, Basic and Diluted [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, 2015						March 31, 2014
		Income			Weighted	Per Share		Income			Weighted	Per Share
		(Numerator)			Average			(Numerator)			Average
					Shares						Shares
					(Denominator)						(Denominator)
	Basic income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	30,951		148,315	$	0.21	$	25,179		146,425	$	0.17
	Dilutive shares for long-term compensation plans	—			716			—			670
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	30,951		149,031	$	0.21	$	25,179		147,095	$	0.17
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	—		148,315	$	—	$	46,721		146,425	$	0.32
	Dilutive shares for long-term compensation plans	—			716			—			670
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	—		149,031	$	—	$	46,721		147,095	$	0.32
	Basic income per common share
	Net income available to common shareholders	$	30,951		148,315	$	0.21	$	71,900		146,425	$	0.49
	Dilutive shares for long-term compensation plans	—			716			—			670
	Diluted income per common share
	Net income available to common shareholders	$	30,951		149,031	$	0.21	$	71,900		147,095	$	0.49
Liberty Property Limited Partnership [Member]
Earnings Per Share, Basic and Diluted [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, 2015						March 31, 2014
		Income (Numerator)			Weighted	Per Unit		Income			Weighted	Per Unit
					Average Units			(Numerator)			Average Units
					(Denominator)						(Denominator)
	Income from continuing operations - net of noncontrolling interest - consolidated joint ventures	$	31,804					$	25,905
	Less: Preferred unit distributions	(118		)				(118		)
	Basic income from continuing operations
	Income from continuing operations available to common unitholders	$	31,686		151,856	$	0.21	$	25,787		149,981	$	0.17
	Dilutive units for long-term compensation plans	—			716			—			670
	Diluted income from continuing operations
	Income from continuing operations available to common unitholders	$	31,686		152,572	$	0.21	$	25,787		150,651	$	0.17
	Basic income from discontinued operations
	Discontinued operations	$	—		151,856	$	—	$	47,848		149,981	$	0.32
	Dilutive units for long-term compensation plans	—			716			—			670
	Diluted income from discontinued operations
	Discontinued operations	$	—		152,572	$	—	$	47,848		150,651	$	0.32
	Basic income per common unit
	Income available to common unitholders	$	31,686		151,856	$	0.21	$	73,635		149,981	$	0.49
	Dilutive units for long-term compensation plans	—			716			—			670
	Diluted income per common unit
	Income available to common unitholders	$	31,686		152,572	$	0.21	$	73,635		150,651	$	0.49

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2015
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 Loss (in thousands):
			Three Months Ended March 31,
			2015			2014
	Foreign Currency Translation:
	Beginning balance		$	(5,823	)	$	8,592
	Translation adjustment		(10,410		)	1,346
	Ending balance		(16,233		)	9,938
	Derivative Instruments:
	Beginning balance		(377		)	1,584
	Unrealized loss		(1,299		)	(871		)
	Reclassification adjustment (1)		352			360
	Ending balance		(1,324		)	1,073
	Total accumulated other comprehensive (loss) income		(17,557		)	11,011
	Less: portion included in noncontrolling interest – operating partnership		211			(454		)
	Total accumulated other comprehensive (loss) income included in shareholders' equity/owners' equity		$	(17,346	)	$	10,557
	-1	Amounts reclassified out of Accumulated Other Comprehensive (Loss) Income/General & Limited Partner's Equity into contractual interest expense.

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2015
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,
			2015			2014
	Operating revenue
		Carolinas	$	9,844		$	8,316
		Chicago/Milwaukee	9,793			8,570
		Houston	12,324			11,867
		Lehigh/Central PA	33,554			29,623
		Minnesota	12,672			13,750
		Orlando	5,264			7,995
		Philadelphia	9,982			9,408
		Richmond/Hampton Roads	10,490			10,068
		South Florida	12,206			12,309
		Southeastern PA	39,238			38,437
		Tampa	13,462			13,173
		United Kingdom	3,725			4,102
		Other	34,398			35,039
	Segment-level operating revenue		206,952			202,657
	Reconciliation to total operating revenues
		Discontinued operations	—			(4,748		)
		Other	(51		)	(279		)
	Total operating revenue		$	206,901		$	197,630
	Net operating income
		Carolinas	$	6,617		$	5,742
		Chicago/Milwaukee	6,743			5,163
		Houston	7,221			7,053
		Lehigh/Central PA	22,971			19,240
		Minnesota	5,985			6,619
		Orlando	3,571			5,492
		Philadelphia	7,022			6,721
		Richmond/Hampton Roads	6,229			5,920
		South Florida	6,829			7,527
		Southeastern PA	20,988			19,600
		Tampa	8,702			8,441
		United Kingdom	2,516			2,850
		Other	22,176			21,731
	Segment-level net operating income		127,570			122,099
	Reconciliation to income from continuing operations
		Interest expense (1)	(34,670		)	(39,764		)
		Depreciation/amortization expense (1) (2)	(43,514		)	(44,536		)
		Impairment - real estate assets	(15,739		)	—
		Gain on property dispositions	2,271			—
		Equity in earnings of unconsolidated joint ventures	6,906			4,159
		General and administrative expense (1) (2)	(12,574		)	(12,401		)
		Discontinued operations excluding interest and gain on property dispositions	—			(2,290		)
		Income taxes (2)	(707		)	(483		)
		Other	2,319			(526		)
	Income from continuing operations		$	31,862		$	26,258
	-1	Includes activity on discontinued operations.
	-2	Excludes costs which are included in determining segment-level net operating income.

Accounting_for_the_Impairment_1

Accounting for the Impairment or Disposal of Long-Lived Assets (Tables)	3 Months Ended
	Mar. 31, 2015
Disposal Group, Including Discontinued Operation, 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 properties classified as discontinued operations through the respective disposition dates is as follows (in thousands):
		Three Months Ended March 31,
		2015		2014
	Revenues	$	—	$	4,748
	Operating expenses	—		(2,495		)
	Interest and other income	—		37
	Interest expense	—		(557		)
	Depreciation and amortization	—		—
	Income before gain on property dispositions	—		1,733
	Gain on property dispositions	—		46,115
	Net income	$	—	$	47,848

Noncontrolling_Interest_Operat1

Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units (Tables)	3 Months Ended
	Mar. 31, 2015
Temporary Equity [Line Items]
Schedule of Temporary Equity [Table Text Block]	As of March 31, 2015, the Company had outstanding the following cumulative preferred units of the Operating Partnership:
	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, 2015
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, 2014 and March 31, 2015 (in thousands):
		Mortgage Loans				Unsecured Notes
		Carrying Value		Fair Value		Carrying Value		Fair Value
	As of December 31, 2014	$	487,301	$	501,231	$	2,509,094	$	2,704,069
	As of March 31, 2015	$	484,584	$	496,873	$	2,607,874	$	2,769,146

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Rental Payments	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, 2015, were as follows (in thousands):
	Year	Amount
	2015	$	507
	2016	686
	2017	686
	2018	686
	2019	686
	2020 through 2034	6,604
	Total	$	9,855

Supplemental_Disclosure_to_Sta1

Supplemental Disclosure to Statements of Cash Flows (Tables)	3 Months Ended
	Mar. 31, 2015
Supplemental Cash Flow Information [Abstract]
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, 2015 and 2014 (amounts in thousands):
		2015			2014
	Write-off of fully depreciated/amortized property and deferred costs	$	14,436		$	11,279
	Write-off of depreciated/amortized property and deferred costs due to sale	$	10,295		$	131,026
	Unrealized loss on cash flow hedge	$	(947	)	$	(511	)
	Changes in accrued development capital expenditures	$	(8,343	)	$	2,280

Organization_and_Basis_of_Pres2

Organization and Basis of Presentation (Narrative) (Details)	Mar. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Ownership interest in operating partnership - Limited Partnership	97.70%

Income_per_Common_Share_of_the2

Income per Common Share of the Trust (Details) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Income from continuing operations net of noncontrolling interest	$30,951	$25,179
Discontinued operations net of noncontrolling interest	0	46,721
Net income available to common shareholders	$30,951	$71,900
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Weighted Average Number of Shares Outstanding, Basic	148,315	146,425
Dilutive shares for long-term compensation plans	716	670
Weighted Average Number of Shares Outstanding, Diluted	149,031	147,095
Common shares [Member]
Earnings Per Share, Basic [Abstract]
Income from Continuing Operations, Per Basic Share	$0.21	$0.17
Income from Discontinued Operations, Per Basic Share	$0	$0.32
Income per common share - basic	$0.21	$0.49
Earnings Per Share, Diluted [Abstract]
Income from Continuing Operations, Per Diluted Share	$0.21	$0.17
Income from Discontinued Operations, Per Diluted Share	$0	$0.32
Income per common share - diluted	$0.21	$0.49

Income_per_Common_Share_of_the3

Income per Common Share of the Trust, Anti-dilutive (Details) (Stock Option [Member])	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Stock Option [Member]
Antidilutive Options Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Options Excluded from Computation of Earnings Per Share	596,000	1,247,000

Income_per_Common_Share_of_the4

Income per Common Share of the Trust, Dilutive (Details) (Stock Option [Member], Common shares [Member])	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Stock Option [Member] | Common shares [Member]
Stock Option Exercises [Line Items]
Amount of Options Exercises in Period	44,000	44,000

Income_per_Common_Unit_of_the_2

Income per Common Unit of the Operating Partnership, Diluted (Details) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Income from continuing operations net of noncontrolling interest	$30,951	$25,179
Discontinued operations	0	47,848
Net income available to common shareholders	30,951	71,900
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Weighted Average Number of Shares Outstanding, Basic	148,315	146,425
Dilutive units for long-term compensation plans	716	670
Weighted Average Number of Shares Outstanding, Diluted	149,031	147,095
Liberty Property Limited Partnership [Member]
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Income from continuing operations net of noncontrolling interest	31,804	25,905
Less: Preferred unit distributions	-118	-118
Income from Continuing Operations available to Common Unitholders	31,686	25,787
Discontinued operations	0	47,848
Net income available to common shareholders	$31,686	$73,635
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Weighted Average Number of Shares Outstanding, Basic	151,856	149,981
Dilutive units for long-term compensation plans	716	670
Weighted Average Number of Shares Outstanding, Diluted	152,572	150,651
Liberty Property Limited Partnership [Member] | Common Units [Member]
Earnings Per Share, Basic [Abstract]
Income from Continuing Operations, Per Basic Share	$0.21	$0.17
Income from Discontinued Operations, Per Basic Share	$0	$0.32
Income per common share - basic	$0.21	$0.49
Earnings Per Share, Diluted [Abstract]
Income from Continuing Operations, Per Diluted Share	$0.21	$0.17
Income from Discontinued Operations, Per Diluted Share	$0	$0.32
Income per common share - diluted	$0.21	$0.49

Income_per_Common_Unit_of_the_3

Income per Common Unit of the Operating Partnership, Anti-dilutive Options (Details) (Stock Option [Member])	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Antidilutive Options Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Options Excluded from Computation of Earnings Per Share	596,000	1,247,000
Liberty Property Limited Partnership [Member]
Antidilutive Options Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Options Excluded from Computation of Earnings Per Share	596,000	1,247,000

Income_per_Common_Unit_of_the_4

Income per Common Unit of the Operations Partnership, Dilutive Options (Details) (Liberty Property Limited Partnership [Member], Stock Option [Member], Common Units [Member])	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Liberty Property Limited Partnership [Member] | Stock Option [Member] | Common Units [Member]
Stock Option Exercises [Line Items]
Amount of Options Exercises in Period	44,000	44,000

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014
Foreign Currency Translation:
Beginning balance	($5,823)		$8,592
Translation adjustment	-10,410		1,346
Ending balance	-16,233		9,938
Derivative Instruments:
Beginning balance	-377		1,584
Unrealized loss	-1,299		-871
Reclassification adjustment	352	[1]	360	[1]
Ending balance	-1,324		1,073
Total accumulated other comprehensive (loss) income	-17,557		11,011
Less: portion included in noncontrolling interest - operating partnership	211		-454
Total accumulated other comprehensive (loss) income included in shareholders' equity/owners' equity	($17,346)		$10,557		($6,252)
[1]	Amounts reclassified out of Accumulated Other Comprehensive (Loss) Income/General & Limited Partner's Equity into contractual interes

Segment_Information_Performanc

Segment Information - Performance of the Reportable Segments Based on Property Level Operating Income (Details) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Segment Reporting Information [Line Items]
Operating revenue	$206,901,000		$197,630,000
Net operating income	51,829,000		59,398,000
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense	-34,670,000		-39,207,000
Depreciation and amortization expense	-59,431,000		-57,589,000
Impairment - real estate assets	-15,739,000		0
Gain on property dispositions	2,271,000		0
Equity in earnings of unconsolidated joint ventures	6,906,000		4,159,000
General and administrative expense	-18,802,000		-18,356,000
Income taxes	-845,000		-531,000
Income from continuing operations	31,862,000		26,258,000
Richmond Hampton Roads [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Impairment - real estate assets	-13,400,000
Southeastern PA [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Impairment - real estate assets	-2,300,000
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenue	0		0
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenue	206,952,000		202,657,000
Net operating income	127,570,000		122,099,000
Operating Segments [Member] | Carolinas [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue	9,844,000		8,316,000
Net operating income	6,617,000		5,742,000
Operating Segments [Member] | Chicago Milwaukee [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue	9,793,000		8,570,000
Net operating income	6,743,000		5,163,000
Operating Segments [Member] | Houston [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue	12,324,000		11,867,000
Net operating income	7,221,000		7,053,000
Operating Segments [Member] | Lehigh Central PA [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue	33,554,000		29,623,000
Net operating income	22,971,000		19,240,000
Operating Segments [Member] | Minnesota [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue	12,672,000		13,750,000
Net operating income	5,985,000		6,619,000
Operating Segments [Member] | Orlando [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue	5,264,000		7,995,000
Net operating income	3,571,000		5,492,000
Operating Segments [Member] | Philadelphia [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue	9,982,000		9,408,000
Net operating income	7,022,000		6,721,000
Operating Segments [Member] | Richmond Hampton Roads [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue	10,490,000		10,068,000
Net operating income	6,229,000		5,920,000
Operating Segments [Member] | South Florida [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue	12,206,000		12,309,000
Net operating income	6,829,000		7,527,000
Operating Segments [Member] | Southeastern PA [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue	39,238,000		38,437,000
Net operating income	20,988,000		19,600,000
Operating Segments [Member] | Tampa [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue	13,462,000		13,173,000
Net operating income	8,702,000		8,441,000
Operating Segments [Member] | United Kingdom [Member] | European Union [Member]
Segment Reporting Information [Line Items]
Operating revenue	3,725,000		4,102,000
Net operating income	2,516,000		2,850,000
Operating Segments [Member] | Other Segments [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue	34,398,000		35,039,000
Net operating income	22,176,000		21,731,000
Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Operating revenue	0		-4,748,000
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenue	-51,000		-279,000
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense	-34,670,000	[1]	-39,764,000	[1]
Depreciation and amortization expense	-43,514,000	[1],[2]	-44,536,000	[1],[2]
Impairment - real estate assets	-15,739,000		0
Gain on property dispositions	2,271,000		0
Equity in earnings of unconsolidated joint ventures	6,906,000		4,159,000
General and administrative expense	-12,574,000	[1],[2]	-12,401,000	[1],[2]
Discontinued operations excluding interest and gain on property dispositions	0		-2,290,000
Income taxes	-707,000	[2]	-483,000	[2]
Other	$2,319,000		($526,000)
[1]	Includes activity on discontinued operations.
[2]	Excludes costs which are included in determining segment-level net operating income.

Segment_Information_Building_A

Segment Information Building Acquisitions and Dispositions (Details) (Land, Buildings and Improvements [Member], USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015
	bldg
Land, Buildings and Improvements [Member]
Acquisitions [Abstract]
Number of real estate properties acquired	0
Dispositions [Abstract]
Proceeds from Sale of Property	$42.20
Number of Real Estate Properties Sold	7

Accounting_for_the_Impairment_2

Accounting for the Impairment or Disposal of Long-Lived Assets (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Gain on property dispositions	$0	$46,115
Net income	0	47,848
Discontinued Operations [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues	0	4,748
Operating expenses	0	-2,495
Interest and other income	0	37
Interest expense	0	-557
Depreciation and amortization	0	0
Income before gain on property dispositions	0	1,733
Gain on property dispositions	0	46,115
Net income	$0	$47,848

Accounting_for_the_Impairment_3

Accounting for the Impairment or Disposal of Long-Lived Assets Asset Impairment (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Property, Plant and Equipment [Line Items]
Impairment - real estate assets	$15,739	$0
Richmond Hampton Roads [Member]
Property, Plant and Equipment [Line Items]
Impairment - real estate assets	13,400
Southeastern PA [Member]
Property, Plant and Equipment [Line Items]
Impairment - real estate assets	$2,300

Noncontrolling_Interests_of_th1

Noncontrolling Interests of the Trust- Narrative (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, except Share data, unless otherwise specified
Redeemable Noncontrolling Interest [Line Items]
Common units, units outstanding not held by the trust	3,539,075	3,553,566
Market value of common units based on closing price	$126.30

Limited_Partners_Equity_of_the1

Limited Partners' Equity of the Operating Partnership - Narrative (Details) (Liberty Property Limited Partnership [Member], USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, except Share data, unless otherwise specified
Liberty Property Limited Partnership [Member]
Limited Partners' Capital Account [Line Items]
Limited Partners' Capital Account, Units Outstanding	3,539,075	3,553,566
market value of the outstanding common units	$126.30

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, 2015	Dec. 31, 2014
Temporary Equity [Line Items]
Cumulative redeemable preferred units of the Operating Partnership outstanding	$7,537	7,537
Series I 2 [Member]
Temporary Equity [Line Items]
Cumulative redeemable preferred units of the Operating Partnership outstanding	$7,537
Units	301,483	301,483
Liquidation Preference	$25
Dividend Rate	6.25%

Indebtedness_Details

Indebtedness (Details) (Senior Notes [Member], USD $)	Mar. 01, 2015
In Millions, unless otherwise specified
5.125% Senior Notes [Member]
Unsecured Notes [Abstract]
Debt Instrument, Repurchased Face Amount	$300
Interest Rate	5.13%
3.75% Senior Notes [Member]
Unsecured Notes [Abstract]
Debt Instrument, Face Amount	$400
Interest Rate	3.75%

Disclosure_of_Fair_Value_of_Fi2

Disclosure of Fair Value of Financial Instruments (Details) (Fair Value, Inputs, Level 3 [Member], USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Estimate of Fair Value Measurement [Member] | Mortgage Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$496,873	$501,231
Estimate of Fair Value Measurement [Member] | Unsecured Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	2,769,146	2,704,069
Portion at Other than Fair Value Measurement [Member] | Mortgage Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	484,584	487,301
Portion at Other than Fair Value Measurement [Member] | Unsecured Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$2,607,874	$2,509,094

Derivative_Instruments_Details

Derivative Instruments (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Interest Rate Derivatives [Abstract]
Number of interest rate swap contracts	3
aggregate notional amount	$103,200,000		$103,600,000
Termination value of interest rate swap, including accrued interest	9,100,000
Interest Rate Cash Flow Hedges [Abstract]
Change in fair value of swaps as a decrease to other comprehensive income	1,299,000	871,000
Amount of loss reclassified into interest expense from AOCI	352,000	360,000
Ineffective portion of the change in the fair value of swaps as an adjustment to interest expense	59,000	18,000
Fair value of interest rate swaps	9,000,000		8,500,000
Amount estimated to be reclassified from accumulated other comprehensive income as an adjustment to interest expense	$1,200,000

Commitments_and_Contingencies_1

Commitments and Contingencies - Future Minimum Rental Payments (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
2015	$507,000
2016	686,000
2017	686,000
2018	686,000
2019	686,000
2020 through 2034	6,604,000
Total	9,855,000
Other Expenses [Abstract]
Operating ground lease expense	$64,000	$47,000

Commitments_and_Contingencies_2

Commitments and Contingencies - Loss Contingencies (Details) (USD $)	Mar. 31, 2015
In Millions, unless otherwise specified
Legal Matters [Abstract]
Loss Contingency, Pending Claims, Number	0
Other [Abstract]
Letter of credit obligations	$4.20

Commitments_and_Contingencies_3

Commitments and Contingencies - Supply Commitments (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Supply Commitment [Line Items]
Development in Process	$269,518,000	$277,411,000
Construction in Progress [Member]
Supply Commitment [Line Items]
Net Rentable Area	3,800,000
Number of Real Estate Properties	21
Total anticipated development cost	412,900,000
Deferred Costs, Leasing, Gross	8,000,000
Construction in Progress [Member] | Comcast Innovation and Technology Center [Member]
Supply Commitment [Line Items]
Net Rentable Area	1,300,000
Total anticipated development cost	932,000,000
Comcast Innovative and Technology Center [Abstract]
Number of equity method investments	2
Number of stories in a high-rise building	59
Number of hotel rooms	222
Anticipated investment in joint ventures	185,000,000
Equity Method Investment, Ownership Percentage	20.00%
Development Not Yet Commenced [Member]
Supply Commitment [Line Items]
Total anticipated development cost	167,000,000
Buildings and land parcels [Member]
Supply Commitment [Line Items]
Remaining amount committed or obligated to pay for the benefit of current or future tenants	14,800,000
Tenant Improvements [Member]
Supply Commitment [Line Items]
Tenant improvements not yet completed	$41,500,000

Commitments_and_Contingencies_4

Commitments and Contingencies - Purchase Commitments (Details) (Land Purchases [Member], USD $)	Mar. 31, 2015
In Millions, unless otherwise specified
Land Purchases [Member]
Long-term Purchase Commitment [Line Items]
Remaining amount commitment to future land purchases	$51

Supplemental_Disclosure_to_Sta2

Supplemental Disclosure to Statements of Cash Flows (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Supplemental Cash Flow Information [Abstract]
Write off of fully depreciated/amortized property and deferred costs	$14,436	$11,279
Write off of depreciated property and deferred costs due to sale	10,295	131,026
Unrealized loss on cash flow hedge	-947	-511
Changes in accrued development capital expenditures	($8,343)	$2,280