Liberty Property Limited Partnership 10-Q 31 Jul 14 2014 Q2 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document	6 Months Ended
	Jun. 30, 2014	Jul. 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	30-Jun-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q2	'
Amendment Flag	'false	'
Entity Common Stock, Shares Outstanding	'	148,100,502
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 $)	Jun. 30, 2014	Dec. 31, 2013
ASSETS	'	'
Land and land improvements	$1,162,397,000	$1,139,455,000
Building and improvements	5,244,783,000	5,144,758,000
Less accumulated depreciation	-1,135,864,000	-1,057,680,000
Operating real estate	5,271,316,000	5,226,533,000
Development in progress	329,685,000	209,187,000
Land held for development	241,196,000	233,055,000
Net real estate	5,842,197,000	5,668,775,000
Cash and cash equivalents	228,678,000	163,414,000
Restricted cash	18,980,000	51,456,000
Accounts receivable	15,272,000	13,900,000
Deferred rent receivable	107,473,000	99,956,000
Deferred financing and leasing costs, net of accumulated amortization (2014, $158,313; 2013, $140,958)	221,121,000	226,607,000
Investments in and advances to unconsolidated joint ventures	203,876,000	179,655,000
Assets held for sale	0	275,957,000
Prepaid expenses and other assets	94,142,000	95,840,000
Total assets	6,731,739,000	6,775,560,000
LIABILITIES	'	'
Mortgage loans	537,338,000	545,306,000
Unsecured notes	2,708,668,000	2,708,213,000
Credit facility	0	0
Accounts payable	56,073,000	70,406,000
Accrued interest	28,530,000	25,777,000
Dividend and distributions payable	71,864,000	71,323,000
Other liabilities	219,050,000	250,819,000
Total liabilities	3,621,523,000	3,671,844,000
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of June 30, 2014 and December 31, 2013	7,537,000	7,537,000
EQUITY	'	'
Common shares of beneficial interest, $.001 par value, 283,987,000 shares authorized; 149,008,030 (includes 1,249,909 in treasury) and 147,846,801 (includes 1,249,909 in treasury) shares issued and outstanding as of June 30, 2014 and December 31, 2013, respectively	149,000	148,000
Additional paid-in capital	3,709,753,000	3,669,618,000
Accumulated other comprehensive loss	15,752,000	9,742,000
Distributions in excess of net income	-630,706,000	-591,713,000
Common shares in treasury, at cost, 1,249,909 shares as of June 30, 2014 and December 31, 2013	-51,951,000	-51,951,000
Total Liberty Property Trust shareholders' equity	3,042,997,000	3,035,844,000
Noncontrolling interest - operating partnership	'	'
Noncontrolling interest - consolidated joint ventures	3,919,000	3,622,000
Total equity	3,102,679,000	3,096,179,000
Total liabilities, noncontrolling interest - operating partnership and equity	6,731,739,000	6,775,560,000
Limited partners’ equity – 3,553,566 and 3,556,556 common units outstanding as of June 30, 2014 and December 31, 2013, respectively	'	'
Noncontrolling interest - operating partnership	'	'
Noncontrolling interest - operating partnerships	55,763,000	56,713,000
Liberty Property Limited Partnership [Member]	'	'
ASSETS	'	'
Land and land improvements	1,162,397,000	1,139,455,000
Building and improvements	5,244,783,000	5,144,758,000
Less accumulated depreciation	-1,135,864,000	-1,057,680,000
Operating real estate	5,271,316,000	5,226,533,000
Development in progress	329,685,000	209,187,000
Land held for development	241,196,000	233,055,000
Net real estate	5,842,197,000	5,668,775,000
Cash and cash equivalents	228,678,000	163,414,000
Restricted cash	18,980,000	51,456,000
Accounts receivable	15,272,000	13,900,000
Deferred rent receivable	107,473,000	99,956,000
Deferred financing and leasing costs, net of accumulated amortization (2014, $158,313; 2013, $140,958)	221,121,000	226,607,000
Investments in and advances to unconsolidated joint ventures	203,876,000	179,655,000
Assets held for sale	0	275,957,000
Prepaid expenses and other assets	94,142,000	95,840,000
Total assets	6,731,739,000	6,775,560,000
LIABILITIES	'	'
Mortgage loans	537,338,000	545,306,000
Unsecured notes	2,708,668,000	2,708,213,000
Credit facility	0	0
Accounts payable	56,073,000	70,406,000
Accrued interest	28,530,000	25,777,000
Dividend and distributions payable	71,864,000	71,323,000
Other liabilities	219,050,000	250,819,000
Total liabilities	3,621,523,000	3,671,844,000
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of June 30, 2014 and December 31, 2013	7,537,000	7,537,000
EQUITY	'	'
General partner’s equity - 147,758,121 (net of 1,249,909 treasury units) and 146,596,892 (net of 1,249,909 treasury units) common units outstanding as of June 30, 2014 and December 31, 2013, respectively	3,042,997,000	3,035,844,000
Noncontrolling interest - operating partnership	'	'
Noncontrolling interest - consolidated joint ventures	3,919,000	3,622,000
Total equity	3,102,679,000	3,096,179,000
Total liabilities, noncontrolling interest - operating partnership and equity	6,731,739,000	6,775,560,000
Liberty Property Limited Partnership [Member] | Limited partners’ equity – 3,553,566 and 3,556,556 common units outstanding as of June 30, 2014 and December 31, 2013, respectively	'	'
EQUITY	'	'
Limited partners' equity	$55,763,000	$56,713,000

Balance_Sheet_Parenthetical_Pa

Balance Sheet Parenthetical (Parentheticals) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Amortized Cost on Deferred Financing and Leasing Costs	$158,313,000	$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	283,987,000	183,987,000
Common Stock, Shares, Issued	149,008,030	147,846,801
Common Stock, Shares, Outstanding	149,008,030	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	$158,313,000	$140,958,000
Limited Partners' Capital Account, Units Outstanding	3,553,566	3,556,556
Preferred Units, Outstanding	0	0
Common Stock, Shares, Outstanding	147,758,121	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		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
OPERATING REVENUE	'	'	'	'
Rental	$139,377	$106,955	$278,311	$211,670
Operating expense reimbursement	53,582	44,069	112,263	86,480
Total operating revenue	192,959	151,024	390,574	298,150
OPERATING EXPENSE	'	'	'	'
Rental property	31,928	26,684	70,489	51,913
Real estate taxes	25,716	18,906	50,217	36,863
General and administrative	14,973	16,455	33,334	36,248
Depreciation and amortization	57,872	37,527	114,606	74,748
Total operating expenses	130,489	99,572	268,646	199,772
Operating income	62,470	51,452	121,928	98,378
OTHER INCOME (EXPENSE)	'	'	'	'
Other income	3,117	5,352	5,570	9,732
Interest expense	-38,470	-28,133	-77,677	-55,872
Total other income (expense)	-35,353	-22,781	-72,107	-46,140
Income before gain on property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	27,117	28,671	49,821	52,238
Gain on property dispositions	1,896	0	1,896	0
Income taxes	-693	-660	-1,224	-1,151
Equity in earnings of unconsolidated joint ventures	1,546	1,566	5,705	3,323
Income from continuing operations	29,866	29,577	56,198	54,410
Discontinued operations (including net gain on property dispositions of $140 and $7,658 for the quarters ended June 30, 2014 and 2013, respectively and $46,256 and $49,364 for the six month periods ended June 30, 2014 and 2013, respectively)	241	13,666	48,015	63,489
Net income	30,107	43,243	104,213	117,899
Noncontrolling interest – operating partnership	-821	-3,134	-2,674	-6,551
Noncontrolling interest - consolidated joint ventures	-37	0	-390	0
Net income available to common shareholders	29,249	40,109	101,149	111,348
Comprehensive income attributable to common shareholders	'	'	'	'
Net income	30,107	43,243	104,213	117,899
Other comprehensive income - foreign currency translation	6,464	40	7,811	-4,812
Other comprehensive loss - change in net unrealized gain on derivative instruments	-1,145	0	-1,656	0
Other comprehensive income	5,319	40	6,155	-4,812
Total comprehensive income	35,426	43,283	110,368	113,087
Less: comprehensive income attributable to noncontrolling interest	-983	-3,135	-3,209	-6,406
Comprehensive income attributable to common shareholders	34,443	40,148	107,159	106,681
Basic:	'	'	'	'
Income from continuing operations	$0.20	$0.22	$0.37	$0.42
Income from discontinued operations	$0	$0.11	$0.32	$0.51
Income per common share - basic	$0.20	$0.33	$0.69	$0.93
Diluted:	'	'	'	'
Income from continuing operations	$0.20	$0.22	$0.37	$0.42
Income from discontinued operations	$0	$0.11	$0.32	$0.51
Income per common share - diluted	$0.20	$0.33	$0.69	$0.93
Distributions per common share or unit	$0.48	$0.48	$0.95	$0.95
Weighted average number of common shares outstanding	'	'	'	'
Basic	147,012	120,081	146,749	119,416
Diluted	147,774	120,911	147,444	120,229
Amounts attributable to common shareholders	'	'	'	'
Income from continuing operations	29,014	26,848	54,262	49,751
Discontinued operations	235	13,261	46,887	61,597
Net income available to common shareholders	29,249	40,109	101,149	111,348
Liberty Property Limited Partnership [Member]	'	'	'	'
OPERATING REVENUE	'	'	'	'
Rental	139,377	106,955	278,311	211,670
Operating expense reimbursement	53,582	44,069	112,263	86,480
Total operating revenue	192,959	151,024	390,574	298,150
OPERATING EXPENSE	'	'	'	'
Rental property	31,928	26,684	70,489	51,913
Real estate taxes	25,716	18,906	50,217	36,863
General and administrative	14,973	16,455	33,334	36,248
Depreciation and amortization	57,872	37,527	114,606	74,748
Total operating expenses	130,489	99,572	268,646	199,772
Operating income	62,470	51,452	121,928	98,378
OTHER INCOME (EXPENSE)	'	'	'	'
Other income	3,117	5,352	5,570	9,732
Interest expense	-38,470	-28,133	-77,677	-55,872
Total other income (expense)	-35,353	-22,781	-72,107	-46,140
Income before gain on property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	27,117	28,671	49,821	52,238
Gain on property dispositions	1,896	0	1,896	0
Income taxes	-693	-660	-1,224	-1,151
Equity in earnings of unconsolidated joint ventures	1,546	1,566	5,705	3,323
Income from continuing operations	29,866	29,577	56,198	54,410
Discontinued operations (including net gain on property dispositions of $140 and $7,658 for the quarters ended June 30, 2014 and 2013, respectively and $46,256 and $49,364 for the six month periods ended June 30, 2014 and 2013, respectively)	241	13,666	48,015	63,489
Net income	30,107	43,243	104,213	117,899
Noncontrolling interest - consolidated joint ventures	-37	0	-390	0
Preferred unit distributions	-118	-672	-236	-1,883
Excess of preferred unit redemption over carrying amount	0	-1,236	0	-1,236
Net income available to common shareholders	29,952	41,335	103,587	114,780
Comprehensive income attributable to common shareholders	'	'	'	'
Net income	30,107	43,243	104,213	117,899
Other comprehensive income - foreign currency translation	6,464	40	7,811	-4,812
Other comprehensive loss - change in net unrealized gain on derivative instruments	-1,145	0	-1,656	0
Other comprehensive income	5,319	40	6,155	-4,812
Total comprehensive income	35,426	43,283	110,368	113,087
Basic:	'	'	'	'
Income from continuing operations	$0.20	$0.22	$0.37	$0.42
Income from discontinued operations	$0	$0.11	$0.32	$0.51
Income per common share - basic	$0.20	$0.33	$0.69	$0.93
Diluted:	'	'	'	'
Income from continuing operations	$0.20	$0.22	$0.37	$0.42
Income from discontinued operations	$0	$0.11	$0.32	$0.51
Income per common share - diluted	$0.20	$0.33	$0.69	$0.93
Distributions per common share or unit	$0.48	$0.48	$0.95	$0.95
Weighted average number of common shares outstanding	'	'	'	'
Basic	150,563	123,795	150,304	123,130
Diluted	151,325	124,625	150,999	123,943
Net income allocated to general partners	29,249	40,109	101,149	111,348
Net income allocated to limited partners	821	3,134	2,674	6,551
Amounts attributable to common shareholders	'	'	'	'
Income from continuing operations	29,829	29,577	55,808	54,410
Net income available to common shareholders	$29,952	$41,335	$103,587	$114,780

Income_Statement_Parenthetical

Income Statement Parenthetical (Parentheticals) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Gain on property dispositions	$140	$7,658	$46,256	$49,364
Liberty Property Limited Partnership [Member]	'	'	'	'
Gain on property dispositions	$140	$7,658	$46,256	$49,364

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

31,588,000

1,000

31,587,000

'

'

'

31,588,000

'

'

'

'

'

'

'

'

Net income

104,213,000

'

'

'

101,149,000

'

101,149,000

2,438,000

236,000

390,000

104,213,000

101,149,000

2,438,000

236,000

390,000

Redemption of limited partners common units for common shares

'

'

'

'

'

'

'

'

'

'

0

48,000

-48,000

'

'

Contributions from partners

'

'

'

'

'

'

'

'

'

'

40,088,000

40,088,000

'

'

'

Distributions

-143,956,000

'

'

'

-140,142,000

'

-140,142,000

-3,485,000

-236,000

-93,000

'

'

'

'

'

Distributions to partners

'

'

'

'

'

'

'

'

'

'

-143,956,000

-140,142,000

-3,485,000

-236,000

-93,000

Share-based compensation

8,500,000

'

8,500,000

'

'

'

8,500,000

'

'

'

'

'

'

'

'

Foreign currency translation adjustment

7,811,000

'

'

7,627,000

'

'

7,627,000

184,000

'

'

7,811,000

7,627,000

184,000

'

'

Other comprehensive loss - change in net unrealized gain on derivative instruments

-1,656,000

'

0

-1,617,000

0

0

-1,617,000

-39,000

0

0

-1,656,000

-1,617,000

-39,000

'

'

Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests, Common Units

0

'

48,000

'

'

'

48,000

-48,000

'

'

'

'

'

'

'

Ending Balance at Jun. 30, 2014

3,102,679,000

149,000

3,709,753,000

15,752,000

-630,706,000

-51,951,000

3,042,997,000

55,763,000

0

3,919,000

3,102,679,000

3,042,997,000

55,763,000

0

3,919,000

Beginning Balance at Mar. 31, 2014

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net income

30,107,000

'

'

'

'

'

'

'

'

'

30,107,000

'

'

'

'

Foreign currency translation adjustment

6,464,000

'

'

'

'

'

'

'

'

'

6,464,000

'

'

'

'

Other comprehensive loss - change in net unrealized gain on derivative instruments

-1,145,000

'

'

'

'

'

'

'

'

'

-1,145,000

'

'

'

'

Ending Balance at Jun. 30, 2014

$3,102,679,000

'

'

'

'

'

'

'

'

'

$3,102,679,000

'

'

'

'

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
OPERATING ACTIVITIES	'	'
Net income	$104,213	$117,899
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	116,547	90,956
Amortization of deferred financing costs	2,629	1,964
Equity in earnings of unconsolidated joint ventures	-5,705	-3,323
Distributions from unconsolidated joint ventures	0	470
Gain on property dispositions	-48,152	-49,364
Share-based compensation	8,500	6,359
Other	-2,210	-4,461
Changes in operating assets and liabilities:	'	'
Restricted cash	33,239	5,478
Accounts receivable	-1,307	875
Deferred rent receivable	-7,548	-4,197
Prepaid expenses and other assets	-29,907	1,477
Accounts payable	9,100	1,161
Accrued interest	2,753	-158
Other liabilities	-34,802	-18,727
Net cash provided by operating activities	147,350	146,409
INVESTING ACTIVITIES	'	'
Investment in operating properties - acquisitions	-90,837	-133,500
Investment in operating properties - other	-39,073	-24,104
Investments in and advances to unconsolidated joint ventures	-12,008	-8,153
Distributions from unconsolidated joint ventures	5,429	4,975
Net proceeds from disposition of properties/land	351,299	124,453
Net proceeds from public reimbursement receivable/escrow	5,627	10,845
Investment in development in progress	-150,199	-47,843
Investment in land held for development	-12,793	-13,586
Investment in deferred leasing costs	-18,252	-15,166
Net cash provided by (used in) investing activities	39,193	-102,079
FINANCING ACTIVITIES	'	'
Net proceeds from issuance of common shares	31,588	108,852
Redemption of preferred units	0	-64,500
Proceeds from mortgage loans	0	6,738
Repayments of mortgage loans	-7,013	-2,506
Proceeds from credit facility	0	269,550
Repayments on credit facility	0	-216,550
Increase in deferred financing costs	-3,635	-8
Distribution paid on common shares	-139,598	-113,241
Distribution paid on units	-3,814	-5,827
Net cash used in financing activities	-122,472	-17,492
Net increase in cash and cash equivalents	64,071	26,838
Increase (decrease) in cash and cash equivalents related to foreign currency translation	1,193	-3,515
Cash and cash equivalents at beginning of period	163,414	38,356
Cash and cash equivalents at end of period	228,678	61,679
Liberty Property Limited Partnership [Member]	'	'
OPERATING ACTIVITIES	'	'
Net income	104,213	117,899
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	116,547	90,956
Amortization of deferred financing costs	2,629	1,964
Equity in earnings of unconsolidated joint ventures	-5,705	-3,323
Distributions from unconsolidated joint ventures	0	470
Gain on property dispositions	-48,152	-49,364
Share-based compensation	8,500	6,359
Other	-2,210	-4,461
Changes in operating assets and liabilities:	'	'
Restricted cash	33,239	5,478
Accounts receivable	-1,307	875
Deferred rent receivable	-7,548	-4,197
Prepaid expenses and other assets	-29,907	1,477
Accounts payable	9,100	1,161
Accrued interest	2,753	-158
Other liabilities	-34,802	-18,727
Net cash provided by operating activities	147,350	146,409
INVESTING ACTIVITIES	'	'
Investment in operating properties - acquisitions	-90,837	-133,500
Investment in operating properties - other	-39,073	-24,104
Investments in and advances to unconsolidated joint ventures	-12,008	-8,153
Distributions from unconsolidated joint ventures	5,429	4,975
Net proceeds from disposition of properties/land	351,299	124,453
Net proceeds from public reimbursement receivable/escrow	5,627	10,845
Investment in development in progress	-150,199	-47,843
Investment in land held for development	-12,793	-13,586
Investment in deferred leasing costs	-18,252	-15,166
Net cash provided by (used in) investing activities	39,193	-102,079
FINANCING ACTIVITIES	'	'
Redemption of preferred units	0	-64,500
Proceeds from mortgage loans	0	6,738
Repayments of mortgage loans	-7,013	-2,506
Proceeds from credit facility	0	269,550
Repayments on credit facility	0	-216,550
Increase in deferred financing costs	-3,635	-8
Capital contributions	31,588	108,852
Distributions to partners	-143,412	-119,068
Net cash used in financing activities	-122,472	-17,492
Net increase in cash and cash equivalents	64,071	26,838
Increase (decrease) in cash and cash equivalents related to foreign currency translation	1,193	-3,515
Cash and cash equivalents at beginning of period	163,414	38,356
Cash and cash equivalents at end of period	$228,678	$61,679

Organization_and_Basis_of_Pres

Organization and Basis of Presentation	6 Months Ended
	Jun. 30, 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 97.7% of the common equity of the Operating Partnership at June 30, 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 ("FASB") 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. Generally, the sale of a real estate asset would not meet the discontinued operations criteria and would not be presented as such under ASU 2014-08. 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.
	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.

Income_per_Common_Share_of_the

Income per Common Share of the Trust	6 Months Ended
	Jun. 30, 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
		June 30, 2014					June 30, 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	$	29,014	147,012	$	0.2	$	26,848	120,081	$	0.22
	Dilutive shares for long-term compensation plans	—		762			—		830
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	29,014	147,774	$	0.2	$	26,848	120,911	$	0.22
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	235	147,012	$	—	$	13,261	120,081	$	0.11
	Dilutive shares for long-term compensation plans	—		762			—		830
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	235	147,774	$	—	$	13,261	120,911	$	0.11
	Basic income per common share
	Net income available to common shareholders	$	29,249	147,012	$	0.2	$	40,109	120,081	$	0.33
	Dilutive shares for long-term compensation plans	—		762			—		830
	Diluted income per common share
	Net income available to common shareholders	$	29,249	147,774	$	0.2	$	40,109	120,911	$	0.33
		For the Six Months Ended					For the Six Months Ended
		June 30, 2014					June 30, 2013
		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	$	54,262	146,749	$	0.37	$	49,751	119,416	$	0.42
	Dilutive shares for long-term compensation plans	—		695			—		813
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	54,262		147,444	$	0.37	49,751		120,229	$	0.42
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	46,887		146,749	$	0.32	61,597		119,416	$	0.51
	Dilutive shares for long-term compensation plans	—		695			—		813
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	46,887		147,444	$	0.32	61,597		120,229	$	0.51
	Basic income per common share
	Net income available to common shareholders	101,149		146,749	$	0.69	111,348		119,416	$	0.93
	Dilutive shares for long-term compensation plans	—		695			—		813
	Diluted income per common share
	Net income available to common shareholders	$	101,149	147,444	$	0.69	$	111,348	120,229	$	0.93
	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 was 750,000 for both the three and six months ended June 30, 2014 as compared to 625,000 and 773,000, respectively, for the same periods in 2013.
	During the three and six months ended June 30, 2014, 42,000 and 43,000 common shares, respectively, 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	6 Months Ended
	Jun. 30, 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
		June 30, 2014						June 30, 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	$	29,014		147,012	$	0.2	$	26,848		120,081	$	0.22
	Dilutive shares for long-term compensation plans	—			762			—			830
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	29,014		147,774	$	0.2	$	26,848		120,911	$	0.22
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	235		147,012	$	—	$	13,261		120,081	$	0.11
	Dilutive shares for long-term compensation plans	—			762			—			830
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	235		147,774	$	—	$	13,261		120,911	$	0.11
	Basic income per common share
	Net income available to common shareholders	$	29,249		147,012	$	0.2	$	40,109		120,081	$	0.33
	Dilutive shares for long-term compensation plans	—			762			—			830
	Diluted income per common share
	Net income available to common shareholders	$	29,249		147,774	$	0.2	$	40,109		120,911	$	0.33
		For the Six Months Ended						For the Six Months Ended
		June 30, 2014						June 30, 2013
		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	$	54,262		146,749	$	0.37	$	49,751		119,416	$	0.42
	Dilutive shares for long-term compensation plans	—			695			—			813
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	54,262			147,444	$	0.37	49,751			120,229	$	0.42
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	46,887			146,749	$	0.32	61,597			119,416	$	0.51
	Dilutive shares for long-term compensation plans	—			695			—			813
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	46,887			147,444	$	0.32	61,597			120,229	$	0.51
	Basic income per common share
	Net income available to common shareholders	101,149			146,749	$	0.69	111,348			119,416	$	0.93
	Dilutive shares for long-term compensation plans	—			695			—			813
	Diluted income per common share
	Net income available to common shareholders	$	101,149		147,444	$	0.69	$	111,348		120,229	$	0.93
	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 was 750,000 for both the three and six months ended June 30, 2014 as compared to 625,000 and 773,000, respectively, for the same periods in 2013.
	During the three and six months ended June 30, 2014, 42,000 and 43,000 common shares, respectively, 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
		June 30, 2014						June 30, 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	$	29,829					$	29,577
	Less: Preferred unit distributions	(118		)				(672		)
	Excess of preferred unit redemption over carrying amount	—						(1,236		)
	Basic income from continuing operations
	Income from continuing operations available to common unitholders	$	29,711		150,563	$	0.2	$	27,669		123,795	$	0.22
	Dilutive units for long-term compensation plans	—			762			—			830
	Diluted income from continuing operations
	Income from continuing operations available to common unitholders	$	29,711		151,325	$	0.2	$	27,669		124,625	$	0.22
	Basic income from discontinued operations
	Discontinued operations	$	241		150,563	$	—	$	13,666		123,795	$	0.11
	Dilutive units for long-term compensation plans	—			762			—			830
	Diluted income from discontinued operations
	Discontinued operations	$	241		151,325	$	—	$	13,666		124,625	$	0.11
	Basic income per common unit
	Income available to common unitholders	$	29,952		150,563	$	0.2	$	41,335		123,795	$	0.33
	Dilutive units for long-term compensation plans	—			762			—			830
	Diluted income per common unit
	Income available to common unitholders	$	29,952		151,325	$	0.2	$	41,335		124,625	$	0.33
		For the Six Months Ended						For the Six Months Ended
		June 30, 2014						June 30, 2013
		Income			Weighted	Per Unit		Income			Weighted	Per Unit
		(Numerator)			Average Units			(Numerator)			Average Units
					(Denominator)						(Denominator)
	Income from continuing operations net of noncontrolling interest - consolidated joint ventures	$	55,808					$	54,410
	Less: Preferred unit distributions	(236		)				(1,883		)
	Excess of preferred unit redemption over carrying amount	—						(1,236		)
	Basic income from continuing operations
	Income from continuing operations available to common unitholders	55,572			150,304	$	0.37	51,291			123,130	$	0.42
	Dilutive units for long-term compensation plans	—			695			—			813
	Diluted income from continuing operations
	Income from continuing operations available to common unitholders	55,572			150,999	$	0.37	51,291			123,943	$	0.42
	Basic income from discontinued operations
	Discontinued operations	48,015			150,304	$	0.32	63,489			123,130	$	0.51
	Dilutive units for long-term compensation plans	—			695			—			813
	Diluted income from discontinued operations
	Discontinued operations	48,015			150,999	$	0.32	63,489			123,943	$	0.51
	Basic income per common unit
	Income available to common unitholders	103,587			150,304	$	0.69	114,780			123,130	$	0.93
	Dilutive units for long-term compensation plans	—			695			—			813
	Diluted income per common unit
	Income available to common unitholders	$	103,587		150,999	$	0.69	$	114,780		123,943	$	0.93
	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 was 750,000 for both the three and six months ended June 30, 2014 as compared to 625,000 and 773,000, respectively, for the same periods in 2013.
	During the three and six months ended June 30, 2014, 42,000 and 43,000 common units, respectively, 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	6 Months Ended
	Jun. 30, 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):
		Six Months Ended June 30,
		2014			2013
	Foreign Currency Translation:
	Beginning balance	$	8,592		$	3,195
	Translation adjustment	7,811			(4,812		)
	Ending balance	16,403			(1,617		)
	Net unrealized gain (loss) on derivative instruments:
	Beginning balance	1,584			—
	Unrealized losses	(1,656		)	—
	Ending balance	(72		)	—
	Total accumulated other comprehensive income (loss)	16,331			(1,617		)
	Less: portion included in noncontrolling interest – operating partnership	(579		)	(150		)
	Total accumulated other comprehensive income (loss) included in shareholders' equity	$	15,752		$	(1,767	)

Segment_Information

Segment Information	6 Months Ended
	Jun. 30, 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							For the Six Months
				Ended June 30,							Ended June 30,
				2014				2013			2014			2013
	Operating revenue
		Carolinas		$	8,486			$	7,309		$	16,803		$	14,587
		Chicago/Milwaukee		8,152				3,470			16,723			6,163
		Houston		12,128				9,018			23,995			17,353
		Lehigh/Central PA		28,195				24,681			57,819			49,358
		Minnesota		13,541				15,345			27,292			30,728
		Orlando		8,061				7,876			16,056			15,573
		Philadelphia		8,691				7,061			18,099			15,394
		Richmond/Hampton Roads		10,115				9,794			20,184			19,940
		South Florida		11,707				8,676			24,016			17,234
		Southeastern PA		36,309				40,389			74,746			81,443
		Tampa		13,230				13,116			26,404			26,082
		United Kingdom		4,218				1,120			8,320			2,220
		Other		30,122				30,716			65,158			60,446
	Segment-level operating revenue			192,955				178,571			395,615			356,521
	Reconciliation to total operating revenues
		Discontinued operations		28				(27,516		)	(4,735		)	(58,597		)
		Other		(24		)		(31		)	(306		)	226
	Total operating revenue			$	192,959			$	151,024		$	390,574		$	298,150
	Net operating income
		Carolinas		$	5,693			$	4,939		$	11,435		$	9,853
		Chicago/Milwaukee		4,973				1,812			10,136			3,986
		Houston		7,232				5,058			14,284			10,309
		Lehigh/Central PA		19,773				16,550			39,013			33,218
		Minnesota		6,770				7,562			13,390			15,274
		Orlando		5,354				5,125			10,846			10,376
		Philadelphia		6,790				5,071			13,511			10,950
		Richmond/Hampton Roads		6,054				5,853			11,973			12,079
		South Florida		6,891				4,858			14,418			9,433
		Southeastern PA		20,060				22,255			39,660			44,868
		Tampa		8,488				8,353			16,929			16,607
		United Kingdom		2,722				(321		)	6,248			(455		)
		Other		19,167				15,665			40,898			32,792
	Segment-level net operating income			119,967				102,780			242,741			209,290
	Reconciliation to income from continuing operations
		Interest expense (1)		(38,470		)		(32,138		)	(78,234		)	(64,220		)
		Depreciation/amortization expense (2)		(44,561		)		(29,061		)	(89,098		)	(58,368		)
		Gain on property dispositions		1,896				—			1,896			—
		Equity in earnings of unconsolidated joint ventures		1,546				1,566			5,705			3,323
		General and administrative expense (2)		(8,232		)		(8,945		)	(20,633		)	(22,821		)
		Discontinued operations excluding gain on property dispositions		(101		)		(6,008		)	(1,759		)	(14,125		)
		Income taxes (2)		(663		)		(645		)	(1,146		)	(1,136		)
	Other		(1,516		)		2,028			(3,274		)	2,467
Income from continuing operations			$	29,866			$	29,577		$	56,198		$	54,410
-1	Includes interest on discontinued operations.
-2	Excludes costs which are included in determining segment-level net operating income.
During the three months ended June 30, 2014, the Company acquired six properties for a total purchase price of $53.2 million. During the six months ended June 30, 2014, the Company acquired eight properties for a total purchase price of $90.9 million.
During the three months ended June 30, 2014, the Company sold three operating properties to a joint venture in which the Company retains a 25% interest for $32.2 million. During the six months ended June 30, 2014, the Company realized proceeds of $366.9 million from the sale of 52 properties and 19 acres of land.
The Company's total assets by reportable segment as of June 30, 2014 and December 31, 2013 is as follows (in thousands):
		June 30,				December 31,
		2014				2013
Total assets
	Carolinas	$	303,215			$	257,230
	Chicago/Milwaukee	416,197				413,585
	Houston	401,045				380,248
	Lehigh/Central PA	972,962				938,824
	Minnesota	343,894				335,613
	Orlando	255,915				253,888
	Philadelphia	336,783				316,810
	Richmond/Hampton Roads	248,446				250,008
	South Florida	379,976				380,138
	Southeastern PA	699,676				695,966
	Tampa	336,012				337,300
	United Kingdom	265,018				247,537
	Other	1,504,110				1,735,393
Segment-level total assets		6,463,249				6,542,540
	Corporate Other	268,490				233,020
Total assets		$	6,731,739			$	6,775,560

Accounting_for_the_Impairment_

Accounting for the Impairment or Disposal of Long-Lived Assets	6 Months Ended
	Jun. 30, 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 disposition of properties excluding the Portfolio Sale that were included in discontinued operations were zero for the three and six months ended June 30, 2014 and were $51.4 million and $126.0 million for the same periods in 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						For the Six Months Ended
			June 30, 2014			June 30, 2013			June 30, 2014			June 30, 2013
	Portfolio Sale
		Revenues	$	(28	)	$	26,659		$	4,733		$	53,800
		Operating expenses	129			(9,113		)	(2,441		)	(18,549		)
		Interest and other income	—			57			29			106
		Interest expense	—			(3,720		)	(557		)	(7,472		)
		Depreciation and amortization	—			(7,293		)	—			(14,604		)
		Income before gain on property dispositions	101			6,590			1,764			13,281
		Gain on property dispositions	80			—			46,121			—
		Income from discontinued operations - Portfolio Sale	$	181		$	6,590		$	47,885		$	13,281
		Noncontrolling interest	(4		)	(195		)	(1,144		)	(396		)
		Income from discontinued operations available to common shareholders - Portfolio Sale	$	177		$	6,395		$	46,741		$	12,885
		Add back noncontrolling interest	4			$	195		$	1,144		$	396
		Income from discontinued operations - Portfolio Sale	$	181		$	6,590		$	47,885		$	13,281
		Income from discontinued operations - other properties	60			7,076			130			50,208
		Income from discontinued operations	$	241		$	13,666		$	48,015		$	63,489
	Net cash used in operating activities from the properties included in the Portfolio Sale for the three and six months ended June 30, 2014 was $97,000 and $2.8 million, respectively, compared to net cash provided by operating activities from such properties of $13.3 million and $28.0 million, respectively, for the three and six months ended June 30, 2013. Net cash provided by investing activities from the properties included in the Portfolio Sale for the three and six months ended June 30, 2014 was $50,000 and $313.2 million, respectively, compared to net cash used by investing activities from such properties of $4.0 million and $7.8 million, respectively, for the three and six months ended June 30, 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.
	During the three months ended June 30, 2014, the Company sold three operating properties in a segment grouped into the Company's "Other" category for aggregate proceeds of $32.2 million. During the six months ended June 30, 2014, the Company sold four operating properties in segments grouped into the Company's "Other" category for aggregate proceeds of $37.3 million Under ASU 2014-08, these sold properties have not been classified as discontinued operations.

Noncontrolling_Interests

Noncontrolling Interests	6 Months Ended
	Jun. 30, 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 June 30, 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 June 30, 2014 was $134.8 million.

Limited_Partners_Equity_of_the

Limited Partners' Equity of the Operating Partnership	6 Months Ended
	Jun. 30, 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 June 30, 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 June 30, 2014 was $134.8 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 June 30, 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. 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 June 30, 2014 based on the closing price of the common shares of the Trust at June 30, 2014 was $134.8 million.

Noncontrolling_Interest_Operat

Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units	6 Months Ended
	Jun. 30, 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 June 30, 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	6 Months Ended
	Jun. 30, 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 June 30, 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	6 Months Ended
	Jun. 30, 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 June 30, 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 June 30, 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 June 30, 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 June 30, 2014	$	537,338	$	561,388	$	2,708,668	$	2,850,123

Investment_in_Unconsolidated_J

Investment in Unconsolidated Joint Ventures	6 Months Ended
	Jun. 30, 2014
Equity Method Investments and Joint Ventures [Abstract]	'
Equity Method Investments and Joint Ventures Disclosure [Text Block]	'
	Investment in Unconsolidated Joint Ventures
	Comcast Innovation & Technology Center
	On June 30, 2014, the Company 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 as part of a trophy-class mixed-use development. The 59-story building will include 1.334 million square feet of rentable office space (the "Office") and a 222-room Four Seasons Hotel (the "Hotel").  The Project is expected to be completed during the first quarter of 2018.  Project costs for the development of the Project, exclusive of tenant-funded interior improvements, are anticipated to be approximately $933 million, of which $40 million represents public assistance in the form of grants from the Commonwealth of Pennsylvania and the City of Philadelphia for funding of infrastructure improvements and public spaces.  The Company's investment in the project is expected to be approximately $185 million with 20% ownership in both joint ventures. As of June 30, 2014, the Company's investment in these joint ventures was $14.2 million. This investment is reflected in investments in and advances to unconsolidated joint ventures in the Company's consolidated balance sheet.
	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.
	Comcast Corporation has signed a 20-year lease for 982,275 square feet, or approximately 74% of the office space in the Office.  The Company will manage and lease the Office and Four Seasons Hotels Limited will manage the Hotel.
	Liberty Venture I, LP
	During the three and six months ended June 30, 2014, Liberty Venture I, LP acquired three properties comprising 603,000 square feet from the Company for $32.2 million.

Business_Combination

Business Combination	6 Months Ended
	Jun. 30, 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	6 Months Ended
	Jun. 30, 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 $104.5 million and $105.2 million at June 30, 2014 and December 31, 2013, respectively, and expire at various dates between 2018 and 2020.
	For the three and six months ended June 30, 2014, the effective portion of the change in the fair value of the swaps was a decrease in the amount of $1.5 million and $2.4 million, respectively, 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 $366,000 and $726,000 for the three and six months ended June 30, 2014, respectively. The ineffective portion of the change in the fair value of the Swaps for the three and six months ended June 30, 2014 in the amounts of $37,000 and $55,000, respectively, were recorded as increases to interest expense in the accompanying consolidated statements of comprehensive income.
	The fair value of the Swaps in the amount of $9.1 million and $8.4 million as of June 30, 2014 and December 31, 2013, respectively, 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 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 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 $9.5 million.

Commitments_and_Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 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 June 30, 2014, were as follows (in thousands):
	Year	Amount
	2014 (six months)	$	187
	2015	393
	2016	412
	2017	412
	2018	412
	2019 through 2034	5,627
	Total	$	7,443
	Operating ground lease expense for the three and six months ended June 30, 2014 were $91,000 and $175,000, respectively, as compared to $42,000 and $84,000, respectively, for the same periods 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 June 30, 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 June 30, 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 June 30, 2014, the Company had 17 buildings under development. These buildings are expected to contain, when completed, a total of 5.7 million square feet of leasable space and represent an anticipated aggregate investment of $467.3 million. At June 30, 2014, development in progress totaled $329.7 million. In addition, as of June 30, 2014, the Company had invested $10.8 million in deferred leasing costs related to these development buildings. See Note 12 for details of the Company's commitments related to the development of the Comcast Innovation and Technology Center.
	As of June 30, 2014, the Company was committed to $10.5 million in improvements on certain buildings and land parcels.
	As of June 30, 2014, the Company was committed to $82.8 million in future land purchases.
	As of June 30, 2014, the Company was obligated to pay for tenant improvements not yet completed for a maximum of $40.1 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	6 Months Ended
	Jun. 30, 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 six months ended June 30, 2014 and 2013 (amounts in thousands):
		2014			2013
	Write-off of fully depreciated property and deferred costs	$	20,672		$	17,784
	Write-off of depreciated property and deferred costs due to sale	$	132,707		$	49,618
	Unrealized losses on cash flow hedge	$	(1,656	)	$	—
	Write-off of origination costs relating to preferred unit redemptions	$	—		$	1,236
	Increase in investments in and advances to unconsolidated joint ventures due to disposition activity	$	(11,948	)	$	—
	Changes in accrued development capital expenditures	$	4,280		$	794
	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)	6 Months Ended
	Jun. 30, 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 97.7% of the common equity of the Operating Partnership at June 30, 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)	6 Months Ended
	Jun. 30, 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
		June 30, 2014					June 30, 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	$	29,014	147,012	$	0.2	$	26,848	120,081	$	0.22
	Dilutive shares for long-term compensation plans	—		762			—		830
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	29,014	147,774	$	0.2	$	26,848	120,911	$	0.22
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	235	147,012	$	—	$	13,261	120,081	$	0.11
	Dilutive shares for long-term compensation plans	—		762			—		830
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	235	147,774	$	—	$	13,261	120,911	$	0.11
	Basic income per common share
	Net income available to common shareholders	$	29,249	147,012	$	0.2	$	40,109	120,081	$	0.33
	Dilutive shares for long-term compensation plans	—		762			—		830
	Diluted income per common share
	Net income available to common shareholders	$	29,249	147,774	$	0.2	$	40,109	120,911	$	0.33
		For the Six Months Ended					For the Six Months Ended
		June 30, 2014					June 30, 2013
		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	$	54,262	146,749	$	0.37	$	49,751	119,416	$	0.42
	Dilutive shares for long-term compensation plans	—		695			—		813
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	54,262		147,444	$	0.37	49,751		120,229	$	0.42
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	46,887		146,749	$	0.32	61,597		119,416	$	0.51
	Dilutive shares for long-term compensation plans	—		695			—		813
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	46,887		147,444	$	0.32	61,597		120,229	$	0.51
	Basic income per common share
	Net income available to common shareholders	101,149		146,749	$	0.69	111,348		119,416	$	0.93
	Dilutive shares for long-term compensation plans	—		695			—		813
	Diluted income per common share
	Net income available to common shareholders	$	101,149	147,444	$	0.69	$	111,348	120,229	$	0.93

Income_per_Common_Unit_of_the_1

Income per Common Unit of the Operating Partnership (Tables)	6 Months Ended
	Jun. 30, 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
		June 30, 2014						June 30, 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	$	29,014		147,012	$	0.2	$	26,848		120,081	$	0.22
	Dilutive shares for long-term compensation plans	—			762			—			830
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	$	29,014		147,774	$	0.2	$	26,848		120,911	$	0.22
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	235		147,012	$	—	$	13,261		120,081	$	0.11
	Dilutive shares for long-term compensation plans	—			762			—			830
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	$	235		147,774	$	—	$	13,261		120,911	$	0.11
	Basic income per common share
	Net income available to common shareholders	$	29,249		147,012	$	0.2	$	40,109		120,081	$	0.33
	Dilutive shares for long-term compensation plans	—			762			—			830
	Diluted income per common share
	Net income available to common shareholders	$	29,249		147,774	$	0.2	$	40,109		120,911	$	0.33
		For the Six Months Ended						For the Six Months Ended
		June 30, 2014						June 30, 2013
		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	$	54,262		146,749	$	0.37	$	49,751		119,416	$	0.42
	Dilutive shares for long-term compensation plans	—			695			—			813
	Diluted income from continuing operations
	Income from continuing operations net of noncontrolling interest	54,262			147,444	$	0.37	49,751			120,229	$	0.42
	Basic income from discontinued operations
	Discontinued operations net of noncontrolling interest	46,887			146,749	$	0.32	61,597			119,416	$	0.51
	Dilutive shares for long-term compensation plans	—			695			—			813
	Diluted income from discontinued operations
	Discontinued operations net of noncontrolling interest	46,887			147,444	$	0.32	61,597			120,229	$	0.51
	Basic income per common share
	Net income available to common shareholders	101,149			146,749	$	0.69	111,348			119,416	$	0.93
	Dilutive shares for long-term compensation plans	—			695			—			813
	Diluted income per common share
	Net income available to common shareholders	$	101,149		147,444	$	0.69	$	111,348		120,229	$	0.93
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
		June 30, 2014						June 30, 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	$	29,829					$	29,577
	Less: Preferred unit distributions	(118		)				(672		)
	Excess of preferred unit redemption over carrying amount	—						(1,236		)
	Basic income from continuing operations
	Income from continuing operations available to common unitholders	$	29,711		150,563	$	0.2	$	27,669		123,795	$	0.22
	Dilutive units for long-term compensation plans	—			762			—			830
	Diluted income from continuing operations
	Income from continuing operations available to common unitholders	$	29,711		151,325	$	0.2	$	27,669		124,625	$	0.22
	Basic income from discontinued operations
	Discontinued operations	$	241		150,563	$	—	$	13,666		123,795	$	0.11
	Dilutive units for long-term compensation plans	—			762			—			830
	Diluted income from discontinued operations
	Discontinued operations	$	241		151,325	$	—	$	13,666		124,625	$	0.11
	Basic income per common unit
	Income available to common unitholders	$	29,952		150,563	$	0.2	$	41,335		123,795	$	0.33
	Dilutive units for long-term compensation plans	—			762			—			830
	Diluted income per common unit
	Income available to common unitholders	$	29,952		151,325	$	0.2	$	41,335		124,625	$	0.33
		For the Six Months Ended						For the Six Months Ended
		June 30, 2014						June 30, 2013
		Income			Weighted	Per Unit		Income			Weighted	Per Unit
		(Numerator)			Average Units			(Numerator)			Average Units
					(Denominator)						(Denominator)
	Income from continuing operations net of noncontrolling interest - consolidated joint ventures	$	55,808					$	54,410
	Less: Preferred unit distributions	(236		)				(1,883		)
	Excess of preferred unit redemption over carrying amount	—						(1,236		)
	Basic income from continuing operations
	Income from continuing operations available to common unitholders	55,572			150,304	$	0.37	51,291			123,130	$	0.42
	Dilutive units for long-term compensation plans	—			695			—			813
	Diluted income from continuing operations
	Income from continuing operations available to common unitholders	55,572			150,999	$	0.37	51,291			123,943	$	0.42
	Basic income from discontinued operations
	Discontinued operations	48,015			150,304	$	0.32	63,489			123,130	$	0.51
	Dilutive units for long-term compensation plans	—			695			—			813
	Diluted income from discontinued operations
	Discontinued operations	48,015			150,999	$	0.32	63,489			123,943	$	0.51
	Basic income per common unit
	Income available to common unitholders	103,587			150,304	$	0.69	114,780			123,130	$	0.93
	Dilutive units for long-term compensation plans	—			695			—			813
	Diluted income per common unit
	Income available to common unitholders	$	103,587		150,999	$	0.69	$	114,780		123,943	$	0.93

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Tables)	6 Months Ended
	Jun. 30, 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):
		Six Months Ended June 30,
		2014			2013
	Foreign Currency Translation:
	Beginning balance	$	8,592		$	3,195
	Translation adjustment	7,811			(4,812		)
	Ending balance	16,403			(1,617		)
	Net unrealized gain (loss) on derivative instruments:
	Beginning balance	1,584			—
	Unrealized losses	(1,656		)	—
	Ending balance	(72		)	—
	Total accumulated other comprehensive income (loss)	16,331			(1,617		)
	Less: portion included in noncontrolling interest – operating partnership	(579		)	(150		)
	Total accumulated other comprehensive income (loss) included in shareholders' equity	$	15,752		$	(1,767	)

Segment_Information_Tables

Segment Information (Tables)	6 Months Ended
	Jun. 30, 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							For the Six Months
				Ended June 30,							Ended June 30,
				2014				2013			2014			2013
	Operating revenue
		Carolinas		$	8,486			$	7,309		$	16,803		$	14,587
		Chicago/Milwaukee		8,152				3,470			16,723			6,163
		Houston		12,128				9,018			23,995			17,353
		Lehigh/Central PA		28,195				24,681			57,819			49,358
		Minnesota		13,541				15,345			27,292			30,728
		Orlando		8,061				7,876			16,056			15,573
		Philadelphia		8,691				7,061			18,099			15,394
		Richmond/Hampton Roads		10,115				9,794			20,184			19,940
		South Florida		11,707				8,676			24,016			17,234
		Southeastern PA		36,309				40,389			74,746			81,443
		Tampa		13,230				13,116			26,404			26,082
		United Kingdom		4,218				1,120			8,320			2,220
		Other		30,122				30,716			65,158			60,446
	Segment-level operating revenue			192,955				178,571			395,615			356,521
	Reconciliation to total operating revenues
		Discontinued operations		28				(27,516		)	(4,735		)	(58,597		)
		Other		(24		)		(31		)	(306		)	226
	Total operating revenue			$	192,959			$	151,024		$	390,574		$	298,150
	Net operating income
		Carolinas		$	5,693			$	4,939		$	11,435		$	9,853
		Chicago/Milwaukee		4,973				1,812			10,136			3,986
		Houston		7,232				5,058			14,284			10,309
		Lehigh/Central PA		19,773				16,550			39,013			33,218
		Minnesota		6,770				7,562			13,390			15,274
		Orlando		5,354				5,125			10,846			10,376
		Philadelphia		6,790				5,071			13,511			10,950
		Richmond/Hampton Roads		6,054				5,853			11,973			12,079
		South Florida		6,891				4,858			14,418			9,433
		Southeastern PA		20,060				22,255			39,660			44,868
		Tampa		8,488				8,353			16,929			16,607
		United Kingdom		2,722				(321		)	6,248			(455		)
		Other		19,167				15,665			40,898			32,792
	Segment-level net operating income			119,967				102,780			242,741			209,290
	Reconciliation to income from continuing operations
		Interest expense (1)		(38,470		)		(32,138		)	(78,234		)	(64,220		)
		Depreciation/amortization expense (2)		(44,561		)		(29,061		)	(89,098		)	(58,368		)
		Gain on property dispositions		1,896				—			1,896			—
		Equity in earnings of unconsolidated joint ventures		1,546				1,566			5,705			3,323
		General and administrative expense (2)		(8,232		)		(8,945		)	(20,633		)	(22,821		)
		Discontinued operations excluding gain on property dispositions		(101		)		(6,008		)	(1,759		)	(14,125		)
		Income taxes (2)		(663		)		(645		)	(1,146		)	(1,136		)
		Other		(1,516		)		2,028			(3,274		)	2,467
	Income from continuing operations			$	29,866			$	29,577		$	56,198		$	54,410
	-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 June 30, 2014 and December 31, 2013 is as follows (in thousands):
			June 30,				December 31,
			2014				2013
	Total assets
		Carolinas	$	303,215			$	257,230
		Chicago/Milwaukee	416,197				413,585
		Houston	401,045				380,248
		Lehigh/Central PA	972,962				938,824
		Minnesota	343,894				335,613
		Orlando	255,915				253,888
		Philadelphia	336,783				316,810
		Richmond/Hampton Roads	248,446				250,008
		South Florida	379,976				380,138
		Southeastern PA	699,676				695,966
		Tampa	336,012				337,300
		United Kingdom	265,018				247,537
		Other	1,504,110				1,735,393
	Segment-level total assets		6,463,249				6,542,540
		Corporate Other	268,490				233,020
	Total assets		$	6,731,739			$	6,775,560

Accounting_for_the_Impairment_1

Accounting for the Impairment or Disposal of Long-Lived Assets (Tables)	6 Months Ended
	Jun. 30, 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						For the Six Months Ended
			June 30, 2014			June 30, 2013			June 30, 2014			June 30, 2013
	Portfolio Sale
		Revenues	$	(28	)	$	26,659		$	4,733		$	53,800
		Operating expenses	129			(9,113		)	(2,441		)	(18,549		)
		Interest and other income	—			57			29			106
		Interest expense	—			(3,720		)	(557		)	(7,472		)
		Depreciation and amortization	—			(7,293		)	—			(14,604		)
		Income before gain on property dispositions	101			6,590			1,764			13,281
		Gain on property dispositions	80			—			46,121			—
		Income from discontinued operations - Portfolio Sale	$	181		$	6,590		$	47,885		$	13,281
		Noncontrolling interest	(4		)	(195		)	(1,144		)	(396		)
		Income from discontinued operations available to common shareholders - Portfolio Sale	$	177		$	6,395		$	46,741		$	12,885
		Add back noncontrolling interest	4			$	195		$	1,144		$	396
		Income from discontinued operations - Portfolio Sale	$	181		$	6,590		$	47,885		$	13,281
		Income from discontinued operations - other properties	60			7,076			130			50,208
		Income from discontinued operations	$	241		$	13,666		$	48,015		$	63,489

Noncontrolling_Interest_Operat1

Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units (Tables)	6 Months Ended
	Jun. 30, 2014
Limited Partners' Capital Account - Preferred Units [Line Items]	'
Schedule of Preferred Units [Table Text Block]	'
	As of June 30, 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	%

Disclosure_of_Fair_Value_of_Fi1

Disclosure of Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 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 June 30, 2014	$	537,338	$	561,388	$	2,708,668	$	2,850,123

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2014
Commitments and Contingencies [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 June 30, 2014, were as follows (in thousands):
	Year	Amount
	2014 (six months)	$	187
	2015	393
	2016	412
	2017	412
	2018	412
	2019 through 2034	5,627
	Total	$	7,443

Supplemental_Disclosure_to_Sta1

Supplemental Disclosure to Statements of Cash Flows (Tables)	6 Months Ended
	Jun. 30, 2014
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 six months ended June 30, 2014 and 2013 (amounts in thousands):
		2014			2013
	Write-off of fully depreciated property and deferred costs	$	20,672		$	17,784
	Write-off of depreciated property and deferred costs due to sale	$	132,707		$	49,618
	Unrealized losses on cash flow hedge	$	(1,656	)	$	—
	Write-off of origination costs relating to preferred unit redemptions	$	—		$	1,236
	Increase in investments in and advances to unconsolidated joint ventures due to disposition activity	$	(11,948	)	$	—
	Changes in accrued development capital expenditures	$	4,280		$	794

Organization_and_Basis_of_Pres2

Organization and Basis of Presentation (Narrative) (Details)	Jun. 30, 2014
Organization and Basis of Presentation [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		6 Months Ended		12 Months Ended
In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Income per Common Share of the Trust [Abstract]	'	'	'	'	'
Income from continuing operations net of noncontrolling interest	$29,014	$26,848	$54,262	$49,751	'
Weighted Average Number of Shares Outstanding, Basic	147,012,000	120,081,000	146,749,000	119,416,000	'
Income from Continuing Operations, Per Basic Share	$0.20	$0.22	$0.37	$0.42	'
Dilutive shares for long-term compensation plans	762,000	830,000	695,000	813,000	'
Weighted Average Number of Shares Outstanding, Diluted	147,774,000	120,911,000	147,444,000	120,229,000	'
Income from Continuing Operations, Per Diluted Share	$0.20	$0.22	$0.37	$0.42	'
Income from Discontinued Operations, Net of Tax, Attributable to Parent	235	13,261	46,887	61,597	'
Income from Discontinued Operations, Net of Tax, Per Basic Share	$0	$0.11	$0.32	$0.51	'
Income from discontinued operations	$0	$0.11	$0.32	$0.51	'
Net income available to common shareholders	$29,249	$40,109	$101,149	$111,348	'
Earnings Per Share, Basic	$0.20	$0.33	$0.69	$0.93	'
Earnings Per Share, Diluted	$0.20	$0.33	$0.69	$0.93	'
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]	'	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	750,000	625,000	750,000	773,000	'
Stock Issued During Period, Shares, Stock Options Exercised	42,000	'	43,000	'	504,000

Income_per_Common_Unit_of_the_2

Income per Common Unit of the Operating Partnership (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Income Per Common Unit [Line Items]	'	'	'	'	'
Income from continuing operations	$29,014	$26,848	$54,262	$49,751	'
Weighted Average Number of Shares Outstanding, Basic	147,012,000	120,081,000	146,749,000	119,416,000	'
Income from Continuing Operations, Per Basic Share	$0.20	$0.22	$0.37	$0.42	'
Dilutive units for long-term compensation plans	762,000	830,000	695,000	813,000	'
Weighted Average Number of Shares Outstanding, Diluted	147,774,000	120,911,000	147,444,000	120,229,000	'
Income from Continuing Operations, Per Diluted Share	$0.20	$0.22	$0.37	$0.42	'
Income from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	241	13,666	48,015	63,489	'
Income from Discontinued Operations, Net of Tax, Per Basic Share	$0	$0.11	$0.32	$0.51	'
Income from discontinued operations	$0	$0.11	$0.32	$0.51	'
Income available to common unitholders	29,249	40,109	101,149	111,348	'
Earnings Per Share, Basic	$0.20	$0.33	$0.69	$0.93	'
Earnings Per Share, Diluted	$0.20	$0.33	$0.69	$0.93	'
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]	'	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	750,000	625,000	750,000	773,000	'
Stock Issued During Period, Shares, Stock Options Exercised	42,000	'	43,000	'	504,000
Liberty Property Limited Partnership [Member]	'	'	'	'	'
Income Per Common Unit [Line Items]	'	'	'	'	'
Income from continuing operations	29,829	29,577	55,808	54,410	'
Less: Preferred unit distributions	-118	-672	-236	-1,883	'
Excess of preferred unit redemption over carrying amount	0	-1,236	0	-1,236	'
Income from Continuing Operations available to Common Unitholders	29,711	27,669	55,572	51,291	'
Weighted Average Number of Shares Outstanding, Basic	150,563,000	123,795,000	150,304,000	123,130,000	'
Income from Continuing Operations, Per Basic Share	$0.20	$0.22	$0.37	$0.42	'
Dilutive units for long-term compensation plans	762,000	830,000	695,000	813,000	'
Weighted Average Number of Shares Outstanding, Diluted	151,325,000	124,625,000	150,999,000	123,943,000	'
Income from Continuing Operations, Per Diluted Share	$0.20	$0.22	$0.37	$0.42	'
Income from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	241	13,666	48,015	63,489	'
Income from Discontinued Operations, Net of Tax, Per Basic Share	$0	$0.11	$0.32	$0.51	'
Income from discontinued operations	$0	$0.11	$0.32	$0.51	'
Income available to common unitholders	$29,952	$41,335	$103,587	$114,780	'
Earnings Per Share, Basic	$0.20	$0.33	$0.69	$0.93	'
Earnings Per Share, Diluted	$0.20	$0.33	$0.69	$0.93	'
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]	'	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	750,000	625,000	750,000	773,000	'
Stock Issued During Period, Shares, Stock Options Exercised	42,000	'	43,000	'	504,000

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Cumulative Translation Adjustment Summary [Roll Forward]	'	'	'	'	'
Beginning balance	'	'	$8,592	$3,195	'
Translation adjustment	'	'	7,811	-4,812	'
Ending balance	16,403	-1,617	16,403	-1,617	'
Cumulative Cash Flow Hedge Adjustment Summary [Roll Forward]	'	'	'	'	'
Beginning balance	'	'	1,584	0	'
Unrealized losses	-1,145	0	-1,656	0	'
Ending balance	-72	0	-72	0	'
Total accumulated other comprehensive income	16,331	-1,617	16,331	-1,617	'
Less: portion included in noncontrolling interest - operating partnership	-579	-150	-579	-150	'
Total accumulated other comprehensive income included in shareholders' equity	$15,752	($1,767)	$15,752	($1,767)	$9,742

Segment_Information_Performanc

Segment Information - Performance of the Reportable Segments Based on Property Level Operating Income (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	$192,959,000		$151,024,000		$390,574,000		$298,150,000
Net operating income	62,470,000		51,452,000		121,928,000		98,378,000
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'		'		'		'
Interest expense	-38,470,000		-28,133,000		-77,677,000		-55,872,000
Depreciation and amortization expense	'		'		-116,547,000		-90,956,000
Gain on property dispositions	1,896,000		0		1,896,000		0
Equity in earnings of unconsolidated joint ventures	1,546,000		1,566,000		5,705,000		3,323,000
General and administrative expense	-14,973,000		-16,455,000		-33,334,000		-36,248,000
Income taxes	-693,000		-660,000		-1,224,000		-1,151,000
Income from continuing operations	29,866,000		29,577,000		56,198,000		54,410,000
Intersegment Eliminations [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	0		0		0		0
Operating Segments [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	192,955,000		178,571,000		395,615,000		356,521,000
Net operating income	119,967,000		102,780,000		242,741,000		209,290,000
Operating Segments [Member] | Carolinas [Member] | North America [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	8,486,000		7,309,000		16,803,000		14,587,000
Net operating income	5,693,000		4,939,000		11,435,000		9,853,000
Operating Segments [Member] | Chicago Milwaukee [Member] | North America [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	8,152,000		3,470,000		16,723,000		6,163,000
Net operating income	4,973,000		1,812,000		10,136,000		3,986,000
Operating Segments [Member] | Houston [Member] | North America [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	12,128,000		9,018,000		23,995,000		17,353,000
Net operating income	7,232,000		5,058,000		14,284,000		10,309,000
Operating Segments [Member] | Lehigh Central PA [Member] | North America [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	28,195,000		24,681,000		57,819,000		49,358,000
Net operating income	19,773,000		16,550,000		39,013,000		33,218,000
Operating Segments [Member] | Minnesota [Member] | North America [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	13,541,000		15,345,000		27,292,000		30,728,000
Net operating income	6,770,000		7,562,000		13,390,000		15,274,000
Operating Segments [Member] | Orlando [Member] | North America [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	8,061,000		7,876,000		16,056,000		15,573,000
Net operating income	5,354,000		5,125,000		10,846,000		10,376,000
Operating Segments [Member] | Philadelphia [Member] | North America [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	8,691,000		7,061,000		18,099,000		15,394,000
Net operating income	6,790,000		5,071,000		13,511,000		10,950,000
Operating Segments [Member] | Richmond Hampton Roads [Member] | North America [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	10,115,000		9,794,000		20,184,000		19,940,000
Net operating income	6,054,000		5,853,000		11,973,000		12,079,000
Operating Segments [Member] | South Florida [Member] | North America [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	11,707,000		8,676,000		24,016,000		17,234,000
Net operating income	6,891,000		4,858,000		14,418,000		9,433,000
Operating Segments [Member] | Southeastern PA [Member] | North America [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	36,309,000		40,389,000		74,746,000		81,443,000
Net operating income	20,060,000		22,255,000		39,660,000		44,868,000
Operating Segments [Member] | Tampa [Member] | North America [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	13,230,000		13,116,000		26,404,000		26,082,000
Net operating income	8,488,000		8,353,000		16,929,000		16,607,000
Operating Segments [Member] | United Kingdom [Member] | European Union [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	4,218,000		1,120,000		8,320,000		2,220,000
Net operating income	2,722,000		-321,000		6,248,000		-455,000
Operating Segments [Member] | Other Segments [Member] | North America [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	30,122,000		30,716,000		65,158,000		60,446,000
Net operating income	19,167,000		15,665,000		40,898,000		32,792,000
Discontinued Operations [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	28,000		-27,516,000		-4,735,000		-58,597,000
Corporate, Non-Segment [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating revenue	-24,000		-31,000		-306,000		226,000
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'		'		'		'
Interest expense	-38,470,000	[1]	-32,138,000	[1]	-78,234,000	[1]	-64,220,000	[1]
Depreciation and amortization expense	-44,561,000	[2]	-29,061,000	[2]	-89,098,000	[2]	-58,368,000	[2]
Gain on property dispositions	1,896,000		0		1,896,000		0
Equity in earnings of unconsolidated joint ventures	1,546,000		1,566,000		5,705,000		3,323,000
General and administrative expense	-8,232,000	[2]	-8,945,000	[2]	-20,633,000	[2]	-22,821,000	[2]
Discontinued operations excluding gain on property dispositions	-101,000		-6,008,000		-1,759,000		-14,125,000
Income taxes	-663,000	[2]	-645,000	[2]	-1,146,000	[2]	-1,136,000	[2]
Other	($1,516,000)		$2,028,000		($3,274,000)		$2,467,000
[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 $)	Jun. 30, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]	'	'
Assets	$6,731,739,000	$6,775,560,000
Operating Segments [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	6,463,249,000	6,542,540,000
Corporate, Non-Segment [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	268,490,000	233,020,000
North America [Member] | Operating Segments [Member] | Carolinas [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	303,215,000	257,230,000
North America [Member] | Operating Segments [Member] | Chicago Milwaukee [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	416,197,000	413,585,000
North America [Member] | Operating Segments [Member] | Houston [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	401,045,000	380,248,000
North America [Member] | Operating Segments [Member] | Lehigh Central PA [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	972,962,000	938,824,000
North America [Member] | Operating Segments [Member] | Minnesota [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	343,894,000	335,613,000
North America [Member] | Operating Segments [Member] | Orlando [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	255,915,000	253,888,000
North America [Member] | Operating Segments [Member] | Philadelphia [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	336,783,000	316,810,000
North America [Member] | Operating Segments [Member] | Richmond Hampton Roads [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	248,446,000	250,008,000
North America [Member] | Operating Segments [Member] | South Florida [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	379,976,000	380,138,000
North America [Member] | Operating Segments [Member] | Southeastern PA [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	699,676,000	695,966,000
North America [Member] | Operating Segments [Member] | Tampa [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	336,012,000	337,300,000
North America [Member] | Operating Segments [Member] | Other Segments [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	1,504,110,000	1,735,393,000
European Union [Member] | Operating Segments [Member] | United Kingdom [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	$265,018,000	$247,537,000

Segment_Information_Building_A

Segment Information Building Acquisitions and Dispositions (Details) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014
	bldg	bldg
Land, Buildings and Improvements [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Number of real estate properties acquired	6	8
Total purchase price	$53,200,000	$90,900,000
Number of Real Estate Properties Sold	'	52
Proceeds from Sale of Property	'	366,900,000
Land [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Number of Real Estate Properties Sold	'	19
Equity Method Investee [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Equity Method Investment, Ownership Percentage	25.00%	25.00%
Not Discontinued Operations [Member] | Other Segments [Member] | Land, Buildings and Improvements [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Number of Real Estate Properties Sold	'	4
Proceeds from Sale of Property	'	37,300,000
Not Discontinued Operations [Member] | Other Segments [Member] | Equity Method Investee [Member] | Land, Buildings and Improvements [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Number of Real Estate Properties Sold	3	'
Proceeds from Sale of Property	$32,200,000	'

Accounting_for_the_Impairment_2

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

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

6 Months Ended

3 Months Ended

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Dec. 31, 2013

Nov. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Dec. 31, 2013

Jan. 31, 2014

Jan. 31, 2014

Jan. 31, 2014

Jan. 31, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Discontinued Operations [Member]

Discontinued Operations [Member]

Discontinued Operations [Member]

Discontinued Operations [Member]

Portfolio Sale, Total [Member]

Portfolio Sale, Total [Member]

Portfolio Sale, Total [Member]

Portfolio Sale, Total [Member]

Portfolio Sale, Total [Member]

Portfolio Sale, Total [Member]

Other Properties [Member]

Other Properties [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]

Land, Buildings and Improvements [Member]

Land, Buildings and Improvements [Member]

Equity Method Investee [Member]

properties

Discontinued Operations [Member]

Discontinued Operations [Member]

Discontinued Operations [Member]

Discontinued Operations [Member]

Discontinued Operations [Member]

Discontinued Operations [Member]

Discontinued Operations [Member]

Discontinued Operations [Member]

properties

Other Segments [Member]

Other Segments [Member]

Southeastern PA [Member]

bldg

Other Segments [Member]

Land, Buildings and Improvements [Member]

sqft

acre

Maryland [Member]

New Jersey [Member]

properties

Not Discontinued Operations [Member]

Other Segments [Member]

sqft

properties

properties

sqft

bldg

Not Discontinued Operations [Member]

acre

sqft

bldg

sqft

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

'

'

'

'

'

Number of Real Estate Properties Sold

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

52

4

3

Proceeds from Sale of Property

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0

51,400,000

0

126,000,000

'

'

'

'

'

366,900,000

37,300,000

32,200,000

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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revenues

'

'

'

'

'

'

'

'

'

'

-28,000

26,659,000

4,733,000

53,800,000

'

'

'

'

'

'

'

'

'

'

'

'

Operating expenses

'

'

'

'

'

'

'

'

'

'

129,000

-9,113,000

-2,441,000

-18,549,000

'

'

'

'

'

'

'

'

'

'

'

'

Interest and other income

'

'

'

'

'

'

'

'

'

'

0

57,000

29,000

106,000

'

'

'

'

'

'

'

'

'

'

'

'

Interest expense

'

'

'

'

'

'

'

'

'

'

0

-3,720,000

-557,000

-7,472,000

'

'

'

'

'

'

'

'

'

'

'

'

Depreciation and Amortization

'

'

'

'

'

'

'

'

'

'

0

-7,293,000

0

-14,604,000

'

'

'

'

'

'

'

'

'

'

'

'

Income before gain on property dispositions

'

'

'

'

'

'

'

'

'

'

101,000

6,590,000

1,764,000

13,281,000

'

'

'

'

'

'

'

'

'

'

'

'

Gain on property dispositions

140,000

7,658,000

46,256,000

49,364,000

'

'

'

'

'

'

80,000

0

46,121,000

0

'

'

'

'

'

'

'

'

'

'

'

'

Income from discontinued operations

241,000

13,666,000

48,015,000

63,489,000

241,000

13,666,000

48,015,000

63,489,000

'

'

181,000

6,590,000

47,885,000

13,281,000

60,000

7,076,000

130,000

50,208,000

'

'

'

'

'

'

'

'

Noncontrolling Interest

'

'

'

'

'

'

'

'

'

'

-4,000

-195,000

-1,144,000

-396,000

'

'

'

'

'

'

'

'

'

'

'

'

Income from discontinued operations available to common shareholders

'

'

'

'

'

'

'

'

'

'

177,000

6,395,000

46,741,000

12,885,000

'

'

'

'

'

'

'

'

'

'

'

'

Discontinued Operation, Additional Disclosures [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Disposal Group, Including Discontinued Operation, Operating Cash Flows

'

'

'

'

'

'

'

'

'

'

-97,000

13,300,000

-2,800,000

28,000,000

'

'

'

'

'

'

'

'

'

'

'

'

Disposal Group, Including Discontinued Operations, Investing Cash Flows

'

'

'

'

'

'

'

'

'

'

$50,000

($4,000,000)

$313,200,000

($7,800,000)

'

'

'

'

'

'

'

'

'

'

'

'

Noncontrolling_Interests_Narra

Noncontrolling Interests - Narrative (Details) (USD $)	Jun. 30, 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	$134.80	'

Limited_Partners_Equity_of_the1

Limited Partners' Equity of the Operating Partnership - Narrative (Details) (USD $)	Jun. 30, 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	$134.80	'
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	$134.80	'

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	Jun. 30, 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 $)	6 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended		6 Months Ended		6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014
	Y		Line of Credit [Member]	Line of Credit [Member]	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]	Old Credit Facility [Member]	New 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	'	'	'	'
Length of Maturity Extension	1	'	'	'	'	'	'	'	'	'
Line of Credit Facility, Competitive Bid Option, Percentage	'	'	'	'	'	50.00%	'	'	'	'
Line of Credit Facility, Maximum Borrowing Capacity	'	'	'	$500,000,000	$800,000,000	$800,000,000	'	'	'	'
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	'	'	'	'	0.20%	'	'	'	'	'
Borrowed Funds	'	'	'	'	'	'	0.6	'	'	'
Assets	6,731,739,000	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 $)	Jun. 30, 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	$2,708,668	$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	537,338	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	2,850,123	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	$561,388	$573,944

Investment_in_Unconsolidated_J1

Investment in Unconsolidated Joint Ventures (Details) (USD $)	3 Months Ended	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2014
	bldg	bldg
Comcast Innovation and Technology Center [Member]	'	'
Schedule of Equity Method Investments [Line Items]	'	'
Number of equity method investments	2	2
Number of stories in a high-rise building	59	59
development total cost	$933	$933
Public Grant award	40	40
Anticipated investment in joint ventures	185	185
Equity Method Investment, Ownership Percentage	20.00%	20.00%
Real Estate Investments, Joint Ventures	14.2	14.2
Net Rentable Area	1,334,000	1,334,000
Number of hotel rooms	222	222
Land, Buildings and Improvements [Member]	'	'
Schedule of Equity Method Investments [Line Items]	'	'
Number of real estate properties acquired	6	8
Total purchase price	53.2	90.9
Land, Buildings and Improvements [Member] | Liberty Venture I, LP [Member]	'	'
Schedule of Equity Method Investments [Line Items]	'	'
Number of real estate properties acquired	3	3
Net rentable area acquired	603,000	603,000
Total purchase price	$32.20	$32.20
Comcast corporation lease [Member] | Lease Agreements [Member] | Comcast Innovation and Technology Center [Member]	'	'
Schedule of Equity Method Investments [Line Items]	'	'
Length of Lease	'20 years	'
Net Rentable Area	982,275	982,275
Percent of net rentable area	74.00%	74.00%

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	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
Interest Rate Derivatives [Abstract]	'	'	'
Number of interest rate swap contracts	3	3	'
aggregate notional amount	$104,500,000	$104,500,000	$105,200,000
Termination value of interest rate swap, including accrued interest	9,500,000	9,500,000	'
Interest Rate Cash Flow Hedges [Abstract]	'	'	'
Change in fair value of swaps as a decrease to other comprehensive income	1,500,000	2,400,000	'
Amount of loss reclassified into interest expense from AOCI	366,000	726,000	'
Ineffective portion of the change in the fair value of swaps as an adjustment to interest expense	37,000	55,000	'
Fair value of interest rate swaps	9,100,000	9,100,000	8,400,000
Amount estimated to be reclassified from accumulated other comprehensive income as an adjustment to interest expense	$1,400,000	$1,400,000	'

Commitments_and_Contingencies_1

Commitments and Contingencies - Narrative (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Commitments And Contingencies [Line Items]	'	'	'	'	'
Operating ground lease expense	$91,000	$42,000	$175,000	$84,000	'
Loss Contingency, Pending Claims, Number	0	'	0	'	'
Letter of credit obligations	8,100,000	'	8,100,000	'	'
Development in Process	329,685,000	'	329,685,000	'	209,187,000
Construction in Progress [Member]	'	'	'	'	'
Commitments And Contingencies [Line Items]	'	'	'	'	'
Number of Real Estate Properties	17	'	17	'	'
Leasable space of buildings	5,700,000	'	5,700,000	'	'
Anticipated aggregate investment	467,300,000	'	467,300,000	'	'
Deferred Costs, Leasing, Gross	10,800,000	'	10,800,000	'	'
Development Not Yet Commenced [Member]	'	'	'	'	'
Commitments And Contingencies [Line Items]	'	'	'	'	'
Land and building improvements	10,500,000	'	10,500,000	'	'
Land Held for Development [Member]	'	'	'	'	'
Commitments And Contingencies [Line Items]	'	'	'	'	'
Purchase Commitment, Remaining Minimum Amount Committed	82,800,000	'	82,800,000	'	'
Maximum [Member]	'	'	'	'	'
Commitments And Contingencies [Line Items]	'	'	'	'	'
Potential payments for tenant allowances	$40,100,000	'	$40,100,000	'	'

Commitments_and_Contingencies_2

Commitments and Contingencies - Future Minimum Rental Payments (Details) (USD $)	Jun. 30, 2014
In Thousands, unless otherwise specified
Commitments and Contingencies [Abstract]	'
2014 (six months)	$187
2015	393
2016	412
2017	412
2018	412
2019 through 2034	5,627
Total	$7,443

Supplemental_Disclosure_to_Sta2

Supplemental Disclosure to Statements of Cash Flows (Details) (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Supplemental Cash Flow Information [Abstract]	'	'
Write off of fully depreciated property and deferred costs	$20,672	$17,784
Write off of depreciated property and deferred costs due to sale	132,707	49,618
Unrealized losses on cash flow hedge, non cash transaction	-1,656	0
Write-off of preferred units costs due to redemption	0	1,236
Increase in investments in and advances to unconsolidated joint ventures due to disposition activity	-11,948	0
Changes in accrued development capital expenditures	$4,280	$794