Liberty Property Trust (LPT) 10-Q 6 Nov 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document - shares	9 Months Ended
	Sep. 30, 2019	Nov. 04, 2019
Entity Information [Line Items]
Title of 12(g) Security	Common Shares of Beneficial Interest, $0.001 par value
Entity Registrant Name	LIBERTY PROPERTY TRUST
Entity Tax Identification Number	23-7768996
Entity Address, Address Line One	650 East Swedesford Road
Entity Address, City or Town	Wayne,
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19087
Trading Symbol	LPT
City Area Code	610
Local Phone Number	648-1700
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
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	Sep. 30, 2019
Entity File Number	1-13130
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Emerging Growth Company	false
Entity Small Business	false
Amendment Flag	false
Entity Common Stock, Shares Outstanding		157,771,589
Security Exchange Name	NYSE
Document Quarterly Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	MD
Liberty Property Limited Partnership
Entity Information [Line Items]
Entity Registrant Name	LIBERTY PROPERTY LIMITED PARTNERSHIP
Entity Tax Identification Number	23-2766549
Entity Central Index Key	0000921113
Entity File Number	1-13132
Entity Incorporation, State or Country Code	PA

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Real estate:
Land and land improvements	$ 1,393,474	$ 1,236,514
Building and improvements	4,785,171	4,397,049
Less accumulated depreciation	(1,040,249)	(941,299)
Operating real estate	5,138,396	4,692,264
Development in progress	323,790	462,572
Land held for development	303,440	296,244
Net real estate	5,765,626	5,451,080
Cash and cash equivalents	514,882	84,923
Restricted cash	14,006	10,899
Accounts receivable	16,975	14,109
Deferred rent receivable	124,509	111,372
Deferred financing and leasing costs, net of accumulated amortization (September 30, 2019, $192,325; December 31, 2018, $165,553)	162,235	157,823
Investments in and advances to unconsolidated joint ventures	347,880	350,981
Assets held for sale	226,504	502,207
Right of use asset	17,664	0
Prepaid expenses and other assets	148,451	251,000
Total assets	7,338,732	6,934,394
LIABILITIES
Mortgage loans, net	297,326	395,202
Unsecured notes, net	2,633,941	2,285,698
Credit facilities	100,000	411,846
Accounts payable	54,953	62,943
Accrued interest	36,530	22,309
Dividend and distributions payable	65,921	60,560
Lease liabilities	18,379	0
Other liabilities	204,963	270,396
Liabilities held for sale	15,939	21,131
Total liabilities	3,427,952	3,530,085
Noncontrolling interest - operating partnership - 213,483 and 301,483 preferred units outstanding as of September 30, 2019 and December 31, 2018, respectively	5,337	7,537
EQUITY
Common shares of beneficial interest, $.001 par value, 283,987,000 shares authorized; 157,755,598 and 147,899,354 shares issued and outstanding as of September 30, 2019 and December 31, 2018, respectively	158	148
Additional paid-in capital	4,145,822	3,691,778
Accumulated other comprehensive loss	(64,496)	(55,243)
Distributions in excess of net income	(238,629)	(306,822)
Total Liberty Property Trust shareholders’ equity	3,842,855	3,329,861
Noncontrolling interest - operating partnership
Noncontrolling interest – operating partnership - 3,494,049 and 3,520,205 common units outstanding as of September 30, 2019 and December 31, 2018, respectively	62,308	61,471
Noncontrolling interest – consolidated joint ventures	280	5,440
Total equity	3,905,443	3,396,772
Total liabilities, noncontrolling interest - operating partnership and equity	7,338,732	6,934,394
Liberty Property Limited Partnership
Real estate:
Land and land improvements	1,393,474	1,236,514
Building and improvements	4,785,171	4,397,049
Less accumulated depreciation	(1,040,249)	(941,299)
Operating real estate	5,138,396	4,692,264
Development in progress	323,790	462,572
Land held for development	303,440	296,244
Net real estate	5,765,626	5,451,080
Cash and cash equivalents	514,882	84,923
Restricted cash	14,006	10,899
Accounts receivable	16,975	14,109
Deferred rent receivable	124,509	111,372
Deferred financing and leasing costs, net of accumulated amortization (September 30, 2019, $192,325; December 31, 2018, $165,553)	162,235	157,823
Investments in and advances to unconsolidated joint ventures	347,880	350,981
Assets held for sale	226,504	502,207
Right of use asset	17,664	0
Prepaid expenses and other assets	148,451	251,000
Total assets	7,338,732	6,934,394
LIABILITIES
Mortgage loans, net	297,326	395,202
Unsecured notes, net	2,633,941	2,285,698
Credit facilities	100,000	411,846
Accounts payable	54,953	62,943
Accrued interest	36,530	22,309
Dividend and distributions payable	65,921	60,560
Lease liabilities	18,379	0
Other liabilities	204,963	270,396
Liabilities held for sale	15,939	21,131
Total liabilities	3,427,952	3,530,085
Noncontrolling interest - operating partnership - 213,483 and 301,483 preferred units outstanding as of September 30, 2019 and December 31, 2018, respectively	5,337	7,537
EQUITY
General partner’s equity - 157,755,598 and 147,899,354 common units outstanding as of September 30, 2019 and December 31, 2018, respectively	3,842,855	3,329,861
Limited partners’ equity – 3,494,049 and 3,520,205 common units outstanding as of September 30, 2019 and December 31, 2018, respectively	62,308	61,471
Noncontrolling interest - operating partnership
Noncontrolling interest – consolidated joint ventures	280	5,440
Total equity	3,905,443	3,396,772
Total liabilities, noncontrolling interest - operating partnership and equity	$ 7,338,732	$ 6,934,394

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Deferred financing and leasing costs, accumulated amortization	$ 192,325	$ 165,553
Limited Partners' common units outstanding	3,500,000	3,520,205
Common shares of beneficial interest, par value per share	$ 0.001	$ 0.001
Common shares of beneficial interest, shares authorized	283,987,000	283,987,000
Common shares of beneficial interest, shares issued	157,755,598	147,899,354
Common shares of beneficial interest, shares outstanding	157,755,598	147,899,354
Liberty Property Limited Partnership
Deferred financing and leasing costs, accumulated amortization	$ 192,325	$ 165,553
Limited Partners' common units outstanding	3,500,000	3,520,205
Common shares of beneficial interest, shares outstanding	157,755,598	147,899,354
Series I-2
Noncontrolling interest - operating partnership, preferred units outstanding	213,483	301,483
Series I-2 | Liberty Property Limited Partnership
Noncontrolling interest - operating partnership, preferred units outstanding	213,483	301,483

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
REVENUE
Rental revenue	$ 162,912	$ 148,330	$ 479,644	$ 439,812
Development service fee income	257	12,956	2,099	59,132
Total revenue	163,169	161,286	481,743	498,944
EXPENSES
Rental property	12,012	12,871	39,780	39,340
Real estate taxes	23,001	22,693	68,862	65,988
General and administrative	10,186	9,807	35,483	32,747
Leasing expense	3,082	2,610	9,608	8,189
Other Cost and Expense, Operating	3,166	3,169	8,690	7,467
Interest expense	25,791	23,133	76,644	66,189
Depreciation and amortization	43,972	41,004	130,402	120,586
Development service fee expense	168	12,924	1,848	120,799
Impairment charges - real estate assets			99	26,000
Total expenses	121,378	128,211	371,416	487,305
OTHER INCOME (EXPENSE)
Interest and other income	2,630	3,474	13,887	8,737
Gain on property dispositions	15,168	2,002	21,125	54,705
Equity in earnings of unconsolidated joint ventures	1,776	6,766	10,966	20,958
Income from continuing operations before income taxes	61,365	45,317	156,305	96,039
Income taxes	(878)	(444)	(1,449)	(1,884)
Income from continuing operations	60,487	44,873	154,856	94,155
Income from discontinued operations	42,189	109,198	105,905	224,531
Net income	102,676	154,071	260,761	318,686
Noncontrolling interest - operating partnership	(2,309)	(3,696)	(6,126)	(7,738)
Noncontrolling interest - consolidated joint ventures	(3)	(232)	(170)	(1,010)
Net income available to common shareholders	100,364	150,143	254,465	309,938
Comprehensive income attributable to common shareholders
Net income	102,676	154,071	260,761	318,686
Other comprehensive loss - foreign currency translation	(7,056)	(3,015)	(7,574)	(9,221)
Other comprehensive income (loss) - derivative instruments	83	6	(1,887)	493
Other comprehensive income	(6,973)	(3,009)	(9,461)	(8,728)
Total comprehensive income	95,703	151,062	251,300	309,958
Less: comprehensive income attributable to noncontrolling interest	(2,463)	(3,858)	(6,390)	(8,545)
Comprehensive income attributable to parent	$ 93,240	$ 147,204	$ 244,910	$ 301,413
Weighted average number of common shares or units outstanding
Basic (in shares)	150,140	147,324	148,532	147,241
Diluted (in shares)	150,979	148,271	149,383	148,160
Amounts attributable to common shareholders or unitholders
Income from continuing operations net of noncontrolling interest	$ 59,091	$ 43,713	$ 151,150	$ 91,051
Income from discontinued operations	41,273	106,430	103,315	218,887
Net income available to common shareholders	100,364	150,143	254,465	309,938
Liberty Property Limited Partnership
REVENUE
Rental revenue	162,912	148,330	479,644	439,812
Development service fee income	257	12,956	2,099	59,132
Total revenue	163,169	161,286	481,743	498,944
EXPENSES
Rental property	12,012	12,871	39,780	39,340
Real estate taxes	23,001	22,693	68,862	65,988
General and administrative	10,186	9,807	35,483	32,747
Leasing expense	3,082	2,610	9,608	8,189
Other Cost and Expense, Operating	3,166	3,169	8,690	7,467
Interest expense	25,791	23,133	76,644	66,189
Depreciation and amortization	43,972	41,004	130,402	120,586
Development service fee expense	168	12,924	1,848	120,799
Impairment charges - real estate assets			99	26,000
Total expenses	121,378	128,211	371,416	487,305
OTHER INCOME (EXPENSE)
Interest and other income	2,630	3,474	13,887	8,737
Gain on property dispositions	15,168	2,002	21,125	54,705
Equity in earnings of unconsolidated joint ventures	1,776	6,766	10,966	20,958
Income from continuing operations before income taxes	61,365	45,317	156,305	96,039
Income taxes	(878)	(444)	(1,449)	(1,884)
Income from continuing operations	60,487	44,873	154,856	94,155
Income from discontinued operations	42,189	109,198	105,905	224,531
Net income	102,676	154,071	260,761	318,686
Noncontrolling interest - consolidated joint ventures	(3)	(232)	(170)	(1,010)
Preferred unit distributions	(83)	(118)	(251)	(354)
Net income available to common shareholders	102,590	153,721	260,340	317,322
Comprehensive income attributable to common shareholders
Net income	102,676	154,071	260,761	318,686
Other comprehensive loss - foreign currency translation	(7,056)	(3,015)	(7,574)	(9,221)
Other comprehensive income (loss) - derivative instruments	83	6	(1,887)	493
Other comprehensive income	(6,973)	(3,009)	(9,461)	(8,728)
Total comprehensive income	$ 95,703	$ 151,062	$ 251,300	$ 309,958
Weighted average number of common shares or units outstanding
Basic (in shares)	153,646	150,844	152,045	150,761
Diluted (in shares)	154,485	151,791	152,896	151,680
Amounts attributable to common shareholders or unitholders
Income from continuing operations net of noncontrolling interest	$ 60,484	$ 44,865	$ 154,872	$ 93,557
Income from discontinued operations	42,189	108,974	105,719	224,119
Net income available to common shareholders	102,590	153,721	260,340	317,322
Net income allocated to general partners	100,364	150,143	254,465	309,938
Net income allocated to limited partners	$ 2,309	$ 3,696	$ 6,126	$ 7,738
Common Units | Liberty Property Limited Partnership
Basic:
Income from continuing operations (in usd per share)	$ 0.39	$ 0.30	$ 1.02	$ 0.62
Income from discontinued operations (in usd per share)	0.28	0.72	0.69	1.48
Earnings Per Share, Basic	0.67	1.02	1.71	2.10
Diluted:
Income from continuing operations (in usd per share)	0.39	0.29	1.01	0.61
Income from discontinued operations (in usd per share)	0.27	0.72	0.69	1.48
Earnings Per Share, Diluted	0.66	1.01	1.70	2.09
Common shares
Basic:
Income from continuing operations (in usd per share)	0.39	0.30	1.02	0.62
Income from discontinued operations (in usd per share)	0.28	0.72	0.69	1.48
Earnings Per Share, Basic	0.67	1.02	1.71	2.10
Diluted:
Income from continuing operations (in usd per share)	0.39	0.29	1.01	0.61
Income from discontinued operations (in usd per share)	0.27	0.72	0.69	1.48
Earnings Per Share, Diluted	$ 0.66	$ 1.01	$ 1.70	$ 2.09

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Gain (loss) on property dispositions in discontinued operations	$ 37.2	$ 94.9	$ 87.4	$ 184.7
Liberty Property Limited Partnership
Gain (loss) on property dispositions in discontinued operations	$ 37.2	$ 94.9	$ 87.4	$ 184.7

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	COMMON SHARES OF BENEFICIAL INTEREST	ADDITIONAL PAID-IN CAPITAL	ACCUMULATED OTHER COMPREHENSIVE LOSS	DISTRIBUTIONS IN EXCESS OF NET INCOME	TOTAL LIBERTY PROPERTY TRUST SHAREHOLDERS’ EQUITY	NONCONTROLLING INTEREST - OPERATING PARTNERSHIP	NONCONTROLLING INTEREST - CONSOLIDATED JOINT VENTURES	Common shares	Liberty Property Limited Partnership	Liberty Property Limited PartnershipGENERAL PARTNER	Liberty Property Limited PartnershipLIMITED PARTNER	Liberty Property Limited PartnershipNONCONTROLLING INTEREST - CONSOLIDATED JOINT VENTURES	Liberty Property Limited PartnershipTOTAL OWNERS’ EQUITY	Liberty Property Limited PartnershipCommon UnitsGENERAL PARTNER	Liberty Property Limited PartnershipCommon UnitsLIMITED PARTNER	Liberty Property Limited Partnership, Preferred Activity
Common shares outstanding - Beginning Balance (shares) at Dec. 31, 2017									147,450,691
General Partner's units outstanding - Beginning Balance (units) at Dec. 31, 2017															147,450,691
Limited Partners' units outstanding - Beginning Balance (units) at Dec. 31, 2017																3,520,205
Beginning balance at Dec. 31, 2017	$ 3,148,366	$ 147	$ 3,674,978	$ (37,797)	$ (549,970)	$ 3,087,358	$ 56,159	$ 4,849			$ 3,087,358	$ 56,159	$ 4,849	$ 3,148,366
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net proceeds from the issuance of common shares	5,255	1	5,254			5,255
Net proceeds from issuance of common shares (shares)									361,630
Net income	318,332				309,938	309,938	7,384	1,010			309,938	7,384	1,010	318,332
Net income available to common shareholders	309,938									$ 317,322
Contributions from partners											13,654			13,654
Contributions from partners (units)															361,630
Distributions to partners											(177,325)	(4,283)	(432)	(182,040)
Distributions	(182,040)				(177,325)	(177,325)	(4,283)	(432)
Share-based compensation	8,399		8,399			8,399
Other comprehensive loss - foreign currency translation activity	(9,221)			(9,007)		(9,007)	(214)			(9,221)	(9,007)	(214)		(9,221)
Other comprehensive income (loss) - derivative instruments	493			482		482	11			493	482	11		493
Common shares outstanding - Ending Balance (shares) at Sep. 30, 2018									147,812,321
General Partner's units outstanding - Ending Balance (units) at Sep. 30, 2018															147,812,321
Limited Partners' units outstanding - Ending Balance (units) at Sep. 30, 2018																3,520,205
Ending balance at Sep. 30, 2018	3,289,584	148	3,688,631	(46,322)	(417,357)	3,225,100	59,057	5,427			3,225,100	59,057	5,427	3,289,584
Noncontrolling Interest - Operating Partnership (Mezzanine) - Beginning Balance at Dec. 31, 2017	7,537																$ 7,537
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (Mezzanine)	354																354
Distributions	(354)																(354)
Noncontrolling Interest - Operating Partnership (Mezzanine) - Ending Balance at Sep. 30, 2018	7,537																7,537
Common shares outstanding - Beginning Balance (shares) at Jun. 30, 2018									147,796,618
General Partner's units outstanding - Beginning Balance (units) at Jun. 30, 2018															147,796,618
Limited Partners' units outstanding - Beginning Balance (units) at Jun. 30, 2018																3,520,205
Beginning balance at Jun. 30, 2018	3,197,225	148	3,686,505	(43,383)	(508,386)	3,134,884	56,918	5,423			3,134,884	56,918	5,423	3,197,225
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net proceeds from the issuance of common shares	728	0	728			728
Net proceeds from issuance of common shares (shares)									15,703
Net income	153,953				150,143	150,143	3,578	232			150,143	3,578	232	153,953
Net income available to common shareholders	150,143									153,721
Contributions from partners											2,126			2,126
Contributions from partners (units)															15,703
Distributions to partners											(59,114)	(1,369)	(228)	(60,711)
Distributions	(60,711)				(59,114)	(59,114)	(1,369)	(228)
Share-based compensation	1,398		1,398			1,398
Other comprehensive loss - foreign currency translation activity	(3,015)			(2,945)		(2,945)	(70)			(3,015)	(2,945)	(70)		(3,015)
Other comprehensive income (loss) - derivative instruments	6			6		6				$ 6	6	0		6
Common shares outstanding - Ending Balance (shares) at Sep. 30, 2018									147,812,321
General Partner's units outstanding - Ending Balance (units) at Sep. 30, 2018															147,812,321
Limited Partners' units outstanding - Ending Balance (units) at Sep. 30, 2018																3,520,205
Ending balance at Sep. 30, 2018	3,289,584	148	3,688,631	(46,322)	(417,357)	3,225,100	59,057	5,427			3,225,100	59,057	5,427	3,289,584
Noncontrolling Interest - Operating Partnership (Mezzanine) - Beginning Balance at Jun. 30, 2018	7,537																7,537
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (Mezzanine)	118																118
Distributions	(118)																(118)
Noncontrolling Interest - Operating Partnership (Mezzanine) - Ending Balance at Sep. 30, 2018	$ 7,537																7,537
Common shares outstanding - Beginning Balance (shares) at Dec. 31, 2018	147,899,354								147,899,354	147,899,354
General Partner's units outstanding - Beginning Balance (units) at Dec. 31, 2018															147,899,354
Limited Partners' units outstanding - Beginning Balance (units) at Dec. 31, 2018	3,520,205									3,520,205						3,520,205
Beginning balance at Dec. 31, 2018	$ 3,396,772	148	3,691,778	(55,243)	(306,822)	3,329,861	61,471	5,440		$ 3,396,772	3,329,861	61,471	5,440	3,396,772
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net proceeds from the issuance of common shares	462,117	10	462,107	0	0	462,117	0	0
Net proceeds from issuance of common shares (shares)									9,830,088
Net income	260,510	0	0	0			5,875	170			254,464	5,875	170	260,509
Net income available to common shareholders	254,465					254,465				260,340
Contributions from partners											466,945	0	0	466,945
Contributions from partners (units)															9,830,088
Distributions to partners											(186,271)	(4,371)	(167)	(190,809)
Distributions	(190,810)	0	0	0	(186,272)	(186,272)	(4,371)	(167)
Share-based compensation	4,828	0	4,828	0	0	4,828	0	0
Other comprehensive loss - foreign currency translation activity	(7,574)	0	0	(7,410)	0	(7,410)	(164)	0		(7,574)	(7,410)	(164)	0	(7,574)
Other comprehensive income (loss) - derivative instruments	(1,887)	0	0	(1,843)	0	(1,843)	(44)	0		$ (1,887)	(1,843)	(44)	0	(1,887)
Acquisition of noncontrolling interest	$ (18,513)	0	(13,350)	0	0	(13,350)	0	(5,163)			(13,350)	0	(5,163)	(18,513)		$ 0
Redemption of noncontrolling interests - common units (shares)									26,156						26,156
Redemption of noncontrolling interest - common units		0	459	0	0	459	(459)	0
Redemption of limited partners common units for common shares											459	(459)
Redemption of limited partners common units for common shares (units)																(26,156)
Common shares outstanding - Ending Balance (shares) at Sep. 30, 2019	157,755,598								157,755,598	157,755,598
General Partner's units outstanding - Ending Balance (units) at Sep. 30, 2019															157,755,598
Limited Partners' units outstanding - Ending Balance (units) at Sep. 30, 2019	3,500,000									3,500,000						3,494,049
Ending balance at Sep. 30, 2019	$ 3,905,443	158	4,145,822	(64,496)	(238,629)	3,842,855	62,308	280		$ 3,905,443	3,842,855	62,308	280	3,905,443
Noncontrolling Interest - Operating Partnership (Mezzanine) - Beginning Balance at Dec. 31, 2018	7,537									7,537							7,537
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (Mezzanine)	251																251
Distributions	(251)																(251)
Temporary Equity Decrease from Redemption of Units	(2,200)																(2,200)
Noncontrolling Interest - Operating Partnership (Mezzanine) - Ending Balance at Sep. 30, 2019	5,337									5,337							5,337
Common shares outstanding - Beginning Balance (shares) at Jun. 30, 2019									148,258,042
General Partner's units outstanding - Beginning Balance (units) at Jun. 30, 2019															148,258,042
Limited Partners' units outstanding - Beginning Balance (units) at Jun. 30, 2019																3,513,049
Beginning balance at Jun. 30, 2019	3,417,364	148	3,687,085	(57,674)	(274,311)	3,355,248	61,839	277			3,355,248	61,839	277	3,417,364
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net proceeds from the issuance of common shares	457,118	10	457,108	0	0	457,118	0	0
Net proceeds from issuance of common shares (shares)									9,478,556
Net income	102,593	0	0	0	100,364	100,364	2,226	3			100,364	2,226	3	102,593
Net income available to common shareholders	100,364									102,590
Contributions from partners											458,413	0	0	458,413
Contributions from partners (units)															9,478,556
Distributions to partners											(64,682)	(1,272)	0	(65,954)
Distributions	(65,954)	0	0	0	(64,682)	(64,682)	(1,272)	0
Share-based compensation	1,295	0	1,295	0	0	1,295	0	0
Other comprehensive loss - foreign currency translation activity	(7,056)	0	0	(6,903)	0	(6,903)	(153)	0		(7,056)	(6,903)	(153)	0	(7,056)
Other comprehensive income (loss) - derivative instruments	83	0	0	81	0	81	2	0		$ 83	81	2	0	83
Redemption of noncontrolling interests - common units (shares)									19,000						19,000
Redemption of noncontrolling interest - common units	$ 0	0	334	0	0	334	(334)	0
Redemption of limited partners common units for common shares											334	(334)
Redemption of limited partners common units for common shares (units)																(19,000)
Common shares outstanding - Ending Balance (shares) at Sep. 30, 2019	157,755,598								157,755,598	157,755,598
General Partner's units outstanding - Ending Balance (units) at Sep. 30, 2019															157,755,598
Limited Partners' units outstanding - Ending Balance (units) at Sep. 30, 2019	3,500,000									3,500,000						3,494,049
Ending balance at Sep. 30, 2019	$ 3,905,443	$ 158	$ 4,145,822	$ (64,496)	$ (238,629)	$ 3,842,855	$ 62,308	$ 280		$ 3,905,443	$ 3,842,855	$ 62,308	$ 280	$ 3,905,443
Noncontrolling Interest - Operating Partnership (Mezzanine) - Beginning Balance at Jun. 30, 2019	5,337																5,337
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (Mezzanine)	83																83
Distributions	(83)																(83)
Noncontrolling Interest - Operating Partnership (Mezzanine) - Ending Balance at Sep. 30, 2019	$ 5,337									$ 5,337							$ 5,337

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Document Period End Date	Sep. 30, 2019
OPERATING ACTIVITIES
Net income	$ 260,761	$ 318,686
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	132,511	132,276
Amortization of deferred financing costs	3,498	2,876
Expensed pursuit costs	864	1,675
Impairment charges - real estate assets	21,581	26,000
Loss on debt extinguishment	7,618	0
Equity in earnings of unconsolidated joint ventures	(10,966)	(20,958)
Distributions from unconsolidated joint ventures	1,500	0
Gain on property dispositions	(137,577)	(239,394)
Share-based compensation	12,405	12,310
Development service fee accrual	0	61,705
Other	(8,875)	(3,612)
Changes in operating assets and liabilities:
Accounts receivable	(3,069)	(1,543)
Deferred rent receivable	(14,366)	(14,782)
Prepaid expenses and other assets	2,102	29,981
Accounts payable	(4,729)	(6,435)
Accrued interest	14,221	13,695
Other liabilities	(50,874)	(16,035)
Net cash provided by operating activities	226,605	296,445
INVESTING ACTIVITIES
Investment in properties – acquisitions	(208,786)	(293,049)
Investment in properties – other	(31,856)	(34,331)
Investments in and advances to unconsolidated joint ventures	(8,567)	(79,036)
Distributions from unconsolidated joint ventures	20,739	30,055
Net proceeds from disposition of properties/land	412,474	574,542
Investment in development in progress	(165,820)	(165,197)
Investment in land held for development	(60,573)	(171,221)
Payment of deferred leasing costs	(25,173)	(18,452)
Release (deposit) of escrows and other	90,660	(128,910)
Net cash provided by (used in) investing activities	23,098	(285,599)
FINANCING ACTIVITIES
Net proceeds from issuance of common shares	462,117	5,255
Share repurchases, including shares related to tax withholdings	(8,847)	(4,638)
Redemption of preferred units	(2,200)	0
Proceeds from unsecured notes	349,097	0
Repayments of mortgage loans including prepayment penalty	(98,467)	(31,954)
Proceeds from credit facility	250,130	1,187,357
Repayments on credit facility	(561,976)	(975,456)
Payment of deferred financing costs	(2,789)	(15)
Acquisition of noncontrolling interest	(18,513)	0
Distribution paid on common shares	(180,735)	(177,210)
Distributions to partners/noncontrolling interests	(4,960)	(5,130)
Net cash provided by (used in) financing activities	182,857	(1,791)
Net increase in cash, cash equivalents and restricted cash	432,560	9,055
Increase (decrease) in cash, cash equivalents and restricted cash related to foreign currency translation	506	(3,599)
Cash, cash equivalents and restricted cash at beginning of period	95,822	25,685
Cash, cash equivalents and restricted cash at end of period	528,888	31,141
Liberty Property Limited Partnership
OPERATING ACTIVITIES
Net income	260,761	318,686
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	132,511	132,276
Amortization of deferred financing costs	3,498	2,876
Expensed pursuit costs	864	1,675
Impairment charges - real estate assets	21,581	26,000
Loss on debt extinguishment	7,618	0
Equity in earnings of unconsolidated joint ventures	(10,966)	(20,958)
Distributions from unconsolidated joint ventures	1,500	0
Gain on property dispositions	(137,577)	(239,394)
Share-based compensation	12,405	12,310
Development service fee accrual	0	61,705
Other	(8,875)	(3,612)
Changes in operating assets and liabilities:
Accounts receivable	(3,069)	(1,543)
Deferred rent receivable	(14,366)	(14,782)
Prepaid expenses and other assets	2,102	29,981
Accounts payable	(4,729)	(6,435)
Accrued interest	14,221	13,695
Other liabilities	(50,874)	(16,035)
Net cash provided by operating activities	226,605	296,445
INVESTING ACTIVITIES
Investment in properties – acquisitions	(208,786)	(293,049)
Investment in properties – other	(31,856)	(34,331)
Investments in and advances to unconsolidated joint ventures	(8,567)	(79,036)
Distributions from unconsolidated joint ventures	20,739	30,055
Net proceeds from disposition of properties/land	412,474	574,542
Investment in development in progress	(165,820)	(165,197)
Investment in land held for development	(60,573)	(171,221)
Payment of deferred leasing costs	(25,173)	(18,452)
Release (deposit) of escrows and other	90,660	(128,910)
Net cash provided by (used in) investing activities	23,098	(285,599)
FINANCING ACTIVITIES
Redemption of preferred units	(2,200)	0
Proceeds from unsecured notes	349,097	0
Repayments of mortgage loans including prepayment penalty	(98,467)	(31,954)
Proceeds from credit facility	250,130	1,187,357
Repayments on credit facility	(561,976)	(975,456)
Payment of deferred financing costs	(2,789)	(15)
Acquisition of noncontrolling interest	(18,513)	0
Capital contributions	462,117	5,255
Distributions to partners/noncontrolling interests	(194,542)	(186,978)
Net cash provided by (used in) financing activities	182,857	(1,791)
Net increase in cash, cash equivalents and restricted cash	432,560	9,055
Increase (decrease) in cash, cash equivalents and restricted cash related to foreign currency translation	506	(3,599)
Cash, cash equivalents and restricted cash at beginning of period	95,822	25,685
Cash, cash equivalents and restricted cash at end of period	$ 528,888	$ 31,141

Organization and Basis of Prese

Organization and Basis of Presentation	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	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 97.8% of the common equity of the Operating Partnership at September 30, 2019 . The Company owns and operates industrial properties in the United States nationally, as well as in the United Kingdom. Prior to the Company's proposed merger with Prologis, Inc. described in Note 17, the Company had intended to divest its remaining office properties (other than its headquarters) over the next few years and focus its efforts and capital solely on its industrial platform. 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. The Operating Partnership is a variable interest entity (“VIE”) of the Trust as the limited partners do not have substantive kick-out or participating rights. The Trust is the primary beneficiary of the Operating Partnership as it has the power to direct the activities of the Operating Partnership and the rights to absorb 97.8% of the net income of the Operating Partnership. The Trust has no significant assets or liabilities other than its investment in the Operating Partnership. As the Operating Partnership is already consolidated in the balance sheets of the Trust, the identification of this entity as a VIE has no impact on the consolidated financial statements of the Trust. In addition, the Company holds a 20% interest in Liberty/Comcast 1701 JFK Boulevard, LP which was determined to be a VIE. The Company determined that it is not the primary beneficiary as the Company and its third party partner share control of the joint venture. The Company's maximum exposure to loss is equal to its equity investment in the joint venture which was $73.9 million and $75.1 million as of September 30, 2019 and December 31, 2018, respectively. Basis of Presentation The accompanying unaudited consolidated financial statements of the Company have been prepared in accordance with United States generally accepted accounting principles (“U.S. 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 U.S. 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, 2018 . 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. Revenue Recognition In May 2014, the Financial Accounting Standards Board (“FASB”) issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which supersedes nearly all existing revenue recognition guidance (except revenue in the scope of other accounting standards, including standards related to leasing). Subsequently, the FASB issued supplementary standards providing additional guidance and targeted improvements to ASU 2014-09 (collectively, the “Revenue Standards”). The Revenue Standards provide a unified model to determine how revenue is recognized. In accordance with the Revenue Standards, the Company performs the following steps: (i) identify the contract with the customer, (ii) identify the performance obligations within the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations and (v) recognize revenue when (or as) a performance obligation is satisfied. Upon adoption of the Revenue Standards, the Company evaluated each of its revenue streams: lease agreement revenue, development service fee revenue, deferred land sale revenue and gain or loss on sale of nonfinancial assets. The Company concluded that there are no revenue streams from its lease agreements that are covered by the Revenue Standards with the possible exception of non-lease components as further discussed below. The Revenue Standards did not have an impact on the amount and timing of recognizing the Company's development service fee income. The Company recognizes development service fee income on a variable basis as a percentage of costs incurred on third party development contracts. Property development services, which are a single performance obligation, continue to be satisfied and recognized over time. The Company measures its progress toward completing the performance obligations under each arrangement. The measurement of the transfer of value to the customer for these services utilizes the input method (actual costs incurred against anticipated project costs) since this method best depicts the actual transfer of value promised to the customer. Estimated expected losses on such contracts are accrued in the period in which they are determinable. The total amount of consideration to be received from these projects is assessed on a quarterly basis. Based on existing contracts, substantial completion is anticipated during 2020. The Company recognizes revenues from improving land sites and selling the underlying land on behalf of its development partner to home builders in the United Kingdom. These agreements typically contain a pre-emption clause and a seller's call option. The Company recognizes revenue as the pre-emption period or seller's call option lapses utilizing the output method. There was $4.5 million and $10.4 million in revenue recognized for such contracts during the three and nine months ended September 30, 2019, respectively. The Revenue Standards did not have an impact on the gain or loss on sale of nonfinancial assets. The Revenue Standards require the Company to derecognize nonfinancial assets once it transfers control of a distinct nonfinancial asset or distinct in-substance nonfinancial asset. Additionally, when the Company transfers its controlling interest in a nonfinancial asset, but retains a noncontrolling ownership interest, the Company is required to measure any noncontrolling interest it receives or retains at fair value. The guidance requires companies to recognize a full gain or loss on the transaction. See Notes 5 and 7 for further discussion of sales of nonfinancial assets during the nine months ended September 30, 2019. Estimated gross revenue related to the remaining performance obligations under existing contracts (before allocation of related costs and expenses) as of September 30, 2019 that will be recognized as revenue in future periods was approximately $28.1 million , which is expected to be recognized in 2019 through 2022. Recently Issued Accounting Standards Leases In February 2016, the FASB issued Accounting Standard Update 2016-02, Leases (“ASU 2016-02”). Additional guidance and targeted improvements to ASU 2016-02 were made through the issuances of supplementary ASUs in July 2018, December 2018 and March 2019 (collectively, the "New Lease Standard"). The New Lease Standard sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). It requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase of the leased asset by the lessee. This classification will determine whether the lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. The New Lease Standard requires lessors to account for leases using an approach that is substantially equivalent to prior guidance for sales type leases, direct financing leases and operating leases. The New Lease Standards limit capitalization of certain initial direct costs which were capitalizable under previous lease standards. Such costs, which were expensed during the three and nine months ended September 30, 2019, were $0.1 million and $0.7 million , respectively. The Company adopted the New Lease Standard on January 1, 2019 and applied it using a modified retrospective approach whereby the cumulative effect of the adoption was recognized on the adoption date and prior periods were not restated. There was no net cumulative effect adjustment to retained earnings as of January 1, 2019 as a result of this adoption. The following practical expedients available for implementation were elected: a. whether an expired or existing contract meets the definition of a lease b. the lease classification at the adoption date for existing or expired leases c. whether costs previously capitalized as initial direct costs would continue to be amortized Additionally, the Company has elected the practical expedient not to recognize right of use assets and lease liabilities with a term of one year or less. The Company's leases met the criteria in the New Lease Standard to not separate non-lease components from the related lease component; therefore, the accounting for these leases remained largely unchanged from the previous standard. The Company has elected to exclude sales and other similar taxes from the measurement of lease revenue and expense and the Company has excluded those costs paid directly by lessees to third parties. Lessee Disclosure As of September 30, 2019, the Company had a total of five properties subject to operating ground leases in Florida, New Jersey, Kentucky and the United Kingdom with a weighted average remaining term of 47 years. These leases have remaining terms of 11 to 110 years, expiration dates of June 2030 to June 2129, and renewal options of 25 to 48 years. The Company has included in the lease terms renewal options up to the useful life of the asset constructed on the land. Payments for certain properties are subject to increases at five year intervals based upon the agreed or appraised fair market value of the leased premises on the adjustment date or the Consumer Price Index percentage increase since the base rent date. These future changes in payments are considered variable payments and do not impact the assessment of the asset or liability unless there is a significant event that triggers reassessment, such as an amendment with a change in the terms of the lease. The Company used discount rates in a range of 4.1% to 5.0% for a weighted average discount rate of 4.6% , which was derived from the Company's assessment of credit quality of the Company adjusted to reflect secured borrowing, estimated yield curves and long-term spread adjustments over appropriate tenures. The Company also leases office space from unrelated third-parties. The Company recognized lease expense of $0.5 million and $1.5 million during the three and nine months ended September 30, 2019, respectively, of which $0.5 million and $1.4 million , respectively, was paid in cash. The following schedule indicates the approximate future minimum lease payments for the ground and office leases as of September 30, 2019: Year Amount (in thousands) 2019 (remainder of year) $ 373 2020 1,370 2021 1,234 2022 1,136 2023 1,035 Thereafter 40,684 Total minimum payments $ 45,832 Imputed interest (26,941 ) Amortization (512 ) Lease liabilities $ 18,379 Deferred rent (715 ) Right of use asset $ 17,664 As noted above, the Company adopted the New Lease Standard effective January 1, 2019. Since the Company has applied the provisions on a modified retrospective basis, the following represents approximate future minimum lease payments by year as of December 31, 2018, as applicable under ASC 840, Leases, prior to the adoption of the New Lease Standard. Year Amount (in thousands) 2019 $ 1,512 2020 1,356 2021 1,205 2022 1,082 2023 981 Thereafter 40,799 $ 46,935 The Company recorded ground lease expense of $1.5 million for the year ended December 31, 2018. Lessor Disclosures The Company leases its operating properties to customers under agreements that are classified as operating leases. It manages residual risk through investing in properties that it believes will appreciate in value over time. Substantially all of the Company's operating leases contain provisions for specified annual increases over the rents of the prior year. Rental income from operating leases is generally recognized on a straight-line basis over the lease term when the Company has determined that the collectibility of substantially all the lease payments is probable. If the Company determines that it is not probable that substantially all of the lease payments will be collected, the Company accounts for the revenue under the lease on a cash basis. Changes in the assessment of probability are accounted for on a cumulative basis as if the lease had always been accounted for based on the current determination of the likelihood of collection potentially resulting in increased volatility of rental revenue. Some of the Company's leases have options to extend, terminate or purchase the facilities, which are considered when determining the lease term. Tenant rights to purchase an underlying asset are typically at prevailing market rates at the time of purchase. The Company does not include in the measurement of lease receivables certain variable payments, including changes in an index, until the specific events that trigger the variable payments have occurred. Generally operating leases require the tenants to reimburse the Company for property tax and other expenditures that are not considered components of the lease and therefore no consideration is allocated to them as they do not result in the transfer of a good or service to the tenants. The Company has determined that all of its leases qualify for the practical expedient to not separate the lease and non-lease components because (i) the lease components are operating leases and (ii) the timing and pattern of recognition of the non-lease components are the same as the lease components. The Company applies the New Lease Standard to the combined component. Income derived from the Company's leases is recorded in rental revenue in the Company's consolidated statements of comprehensive income. Certain tenants are obligated to pay directly their obligations under their leases for real estate taxes, insurance and certain other expenses. These obligations, which have been assumed by the tenants under the terms of their respective leases, are not reflected in the Company's consolidated financial statements. To the extent any tenant responsible for these obligations under the respective lease defaults on its lease or if it is deemed probable that the tenant will fail to pay for such costs, the Company would record a liability for such obligation. The following details the rental income and variable lease income for the three and nine months ended September 30, 2019 (in thousands): Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Rental income - operating leases - continuing operations $ 127,125 $ 371,744 Rental income - operating leases - discontinued operations 6,233 25,481 Variable lease income - operating leases - continuing operations 35,787 107,900 Variable lease income - operating leases - discontinued operations 2,265 8,112 The following amounts reflect the estimated contractual rents due to the Company for the remainder of terms of the Company's operating leases as of September 30, 2019: (in thousands) Remainder of 2019 $ 220,242 2020 500,908 2021 452,679 2022 382,294 2023 314,211 2024 259,139 Thereafter 977,267 Total $ 3,106,740 Other In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities ("ASU 2017-12"). ASU 2017-12 is designed to better align a company’s financial reporting for hedging activities with the economic objectives of those activities. The Company adopted ASU 2017-12 on January 1, 2019 and it did not have a material impact on the Company's consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software: Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract ("ASU 2018-15"). ASU 2018-15 amends the definition of a hosting arrangement and requires a customer in a hosting arrangement that is a service contract to capitalize certain implementation costs as if the arrangement was an internal-use software project. ASU 2018-15 is effective for the Company beginning January 1, 2020. The Company does not anticipate the impact of ASU 2018-15 will have a material impact on the consolidated financial statements.

Income per Common Share of the

Income per Common Share of the Trust	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Income per Common Share of the Trust	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): Three Months Ended Three Months Ended September 30, 2019 September 30, 2018 Income (Numerator) Weighted Average Shares (Denominator) Per Share Income (Numerator) Weighted Average Shares (Denominator) Per Share Income from continuing operations net of noncontrolling interest - basic $ 59,091 150,140 $ 0.39 $ 43,713 147,324 $ 0.30 Dilutive shares for long-term compensation plans — 839 — 947 Income from continuing operations net of noncontrolling interest - diluted $ 59,091 150,979 $ 0.39 $ 43,713 148,271 $ 0.29 Discontinued operations net of noncontrolling interests - basic $ 41,273 150,140 $ 0.28 $ 106,430 147,324 $ 0.72 Dilutive shares for long-term compensation plans — 839 — 947 Discontinued operations net of noncontrolling interests - diluted $ 41,273 150,979 $ 0.27 $ 106,430 148,271 $ 0.72 Net income available to common shareholders - basic $ 100,364 150,140 $ 0.67 $ 150,143 147,324 $ 1.02 Dilutive shares for long-term compensation plans — 839 — 947 Net income available to common shareholders - diluted $ 100,364 150,979 $ 0.66 $ 150,143 148,271 $ 1.01 Nine Months Ended Nine Months Ended September 30, 2019 September 30, 2018 Income Weighted Per Share Income Weighted Per Share Income from continuing operations net of noncontrolling interest - basic $ 151,150 148,532 $ 1.02 $ 91,051 147,241 $ 0.62 Dilutive shares for long-term compensation plans — 851 — 919 Income from continuing operations net of noncontrolling interest - diluted $ 151,150 149,383 $ 1.01 $ 91,051 148,160 $ 0.61 Discontinued operations net of noncontrolling interests - basic $ 103,315 148,532 $ 0.69 $ 218,887 147,241 $ 1.48 Dilutive shares for long-term compensation plans — 851 — 919 Discontinued operations net of noncontrolling interests - diluted $ 103,315 149,383 $ 0.69 $ 218,887 148,160 $ 1.48 Net income available to common shareholders - basic $ 254,465 148,532 $ 1.71 $ 309,938 147,241 $ 2.10 Dilutive shares for long-term compensation plans — 851 — 919 Net income available to common shareholders - diluted $ 254,465 149,383 $ 1.70 $ 309,938 148,160 $ 2.09 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. There were no anti-dilutive options excluded from the computation of diluted income per common share for the three and nine months ended September 30, 2019 or 2018 . During the three and nine months ended September 30, 2019 , 251,000 and 374,000 common shares, respectively, were issued upon the exercise of options. During the year ended December 31, 2018 , 151,000 common shares were issued upon the exercise of options. Equity Offering In September 2019, the Company completed the sale of 9.2 million common shares, at a price of $50.50 per share, for net proceeds of $447.9 million . The net proceeds from this issuance were used to fund the early redemption on October 12, 2019 of the Operating Partnership's $350 million 4.75% senior notes due October 2020, repay outstanding balances on the Company's revolving credit facilities and for general corporate purposes. In conjunction with such early redemption, the Company incurred charges of approximately $9.0 million . Share Repurchase The Company’s Board of Trustees had authorized a share repurchase plan under which the Company may purchase up to $250 million of the Company’s outstanding common shares through September 28, 2019. Purchases made pursuant to the program may be made in either the open market or in privately negotiated transactions from time to time as permitted by securities laws and other legal requirements. There were no purchases under the plan during the three and nine months ended September 30, 2019 or for the year ended December 31, 2018.

Income per Common Unit of the O

Income per Common Unit of the Operating Partnership	9 Months Ended
	Sep. 30, 2019
Earnings Per Unit, Basic and Diluted [Line Items]
Income per Common Share of the Trust	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): Three Months Ended Three Months Ended September 30, 2019 September 30, 2018 Income (Numerator) Weighted Average Shares (Denominator) Per Share Income (Numerator) Weighted Average Shares (Denominator) Per Share Income from continuing operations net of noncontrolling interest - basic $ 59,091 150,140 $ 0.39 $ 43,713 147,324 $ 0.30 Dilutive shares for long-term compensation plans — 839 — 947 Income from continuing operations net of noncontrolling interest - diluted $ 59,091 150,979 $ 0.39 $ 43,713 148,271 $ 0.29 Discontinued operations net of noncontrolling interests - basic $ 41,273 150,140 $ 0.28 $ 106,430 147,324 $ 0.72 Dilutive shares for long-term compensation plans — 839 — 947 Discontinued operations net of noncontrolling interests - diluted $ 41,273 150,979 $ 0.27 $ 106,430 148,271 $ 0.72 Net income available to common shareholders - basic $ 100,364 150,140 $ 0.67 $ 150,143 147,324 $ 1.02 Dilutive shares for long-term compensation plans — 839 — 947 Net income available to common shareholders - diluted $ 100,364 150,979 $ 0.66 $ 150,143 148,271 $ 1.01 Nine Months Ended Nine Months Ended September 30, 2019 September 30, 2018 Income Weighted Per Share Income Weighted Per Share Income from continuing operations net of noncontrolling interest - basic $ 151,150 148,532 $ 1.02 $ 91,051 147,241 $ 0.62 Dilutive shares for long-term compensation plans — 851 — 919 Income from continuing operations net of noncontrolling interest - diluted $ 151,150 149,383 $ 1.01 $ 91,051 148,160 $ 0.61 Discontinued operations net of noncontrolling interests - basic $ 103,315 148,532 $ 0.69 $ 218,887 147,241 $ 1.48 Dilutive shares for long-term compensation plans — 851 — 919 Discontinued operations net of noncontrolling interests - diluted $ 103,315 149,383 $ 0.69 $ 218,887 148,160 $ 1.48 Net income available to common shareholders - basic $ 254,465 148,532 $ 1.71 $ 309,938 147,241 $ 2.10 Dilutive shares for long-term compensation plans — 851 — 919 Net income available to common shareholders - diluted $ 254,465 149,383 $ 1.70 $ 309,938 148,160 $ 2.09 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. There were no anti-dilutive options excluded from the computation of diluted income per common share for the three and nine months ended September 30, 2019 or 2018 . During the three and nine months ended September 30, 2019 , 251,000 and 374,000 common shares, respectively, were issued upon the exercise of options. During the year ended December 31, 2018 , 151,000 common shares were issued upon the exercise of options. Equity Offering In September 2019, the Company completed the sale of 9.2 million common shares, at a price of $50.50 per share, for net proceeds of $447.9 million . The net proceeds from this issuance were used to fund the early redemption on October 12, 2019 of the Operating Partnership's $350 million 4.75% senior notes due October 2020, repay outstanding balances on the Company's revolving credit facilities and for general corporate purposes. In conjunction with such early redemption, the Company incurred charges of approximately $9.0 million . Share Repurchase The Company’s Board of Trustees had authorized a share repurchase plan under which the Company may purchase up to $250 million of the Company’s outstanding common shares through September 28, 2019. Purchases made pursuant to the program may be made in either the open market or in privately negotiated transactions from time to time as permitted by securities laws and other legal requirements. There were no purchases under the plan during the three and nine months ended September 30, 2019 or for the year ended December 31, 2018.
Liberty Property Limited Partnership
Earnings Per Unit, Basic and Diluted [Line Items]
Income per Common Share of the Trust	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): Three Months Ended Three Months Ended September 30, 2019 September 30, 2018 Income (Numerator) Weighted Average Units (Denominator) Per Unit Income (Numerator) Weighted Average Units (Denominator) Per Unit Income from continuing operations - net of noncontrolling interest - consolidated joint ventures $ 60,484 $ 44,865 Less: Preferred unit distributions (83 ) (118 ) Income from continuing operations available to common unitholders - basic $ 60,401 153,646 $ 0.39 $ 44,747 150,844 $ 0.30 Dilutive units for long-term compensation plans — 839 — 947 Income from continuing operations available to common unitholders - diluted $ 60,401 154,485 $ 0.39 $ 44,747 151,791 $ 0.29 Income from discontinued operations net of noncontrolling interest consolidated joint venture - basic $ 42,189 153,646 $ 0.28 $ 108,974 150,844 $ 0.72 Dilutive units for long-term compensation plans — 839 — 947 Income from discontinued operations net of noncontrolling interest consolidated joint venture - basic $ 42,189 154,485 $ 0.27 $ 108,974 151,791 $ 0.72 Income available to common unitholders - basic $ 102,590 153,646 $ 0.67 $ 153,721 150,844 $ 1.02 Dilutive units for long-term compensation plans — 839 — 947 Income available to common unitholders - diluted $ 102,590 154,485 $ 0.66 $ 153,721 151,791 $ 1.01 Nine Months Ended Nine Months Ended September 30, 2019 September 30, 2018 Income (Numerator) Weighted Average Units (Denominator) Per Unit Income (Numerator) Weighted Average Units (Denominator) Per Unit Net income - net of noncontrolling interest - consolidated joint ventures $ 154,872 $ 93,557 Less: Preferred unit distributions (251 ) (354 ) Income from continuing operations available to common unitholders - basic 154,621 152,045 $ 1.02 93,203 150,761 $ 0.62 Dilutive units for long-term compensation plans — 851 — 919 Income from continuing operations available to common unitholders - diluted $ 154,621 152,896 $ 1.01 $ 93,203 151,680 $ 0.61 Income from discontinued operations net of noncontrolling interest consolidated joint venture - basic $ 105,719 152,045 $ 0.69 $ 224,119 150,761 $ 1.48 Dilutive units for long-term compensation plans — 851 — 919 Income from discontinued operations net of noncontrolling interest consolidated joint venture - basic $ 105,719 152,896 $ 0.69 $ 224,119 151,680 $ 1.48 Net income available to common unitholders - basic $ 260,340 152,045 $ 1.71 $ 317,322 150,761 $ 2.10 Dilutive units for long-term compensation plans — 851 — 919 Net income available to common unitholders - diluted $ 260,340 152,896 $ 1.70 $ 317,322 151,680 $ 2.09 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. There were no anti-dilutive options excluded from the computation of diluted income per common unit for the three and nine months ended September 30, 2019 or 2018 . During the three and nine months ended September 30, 2019 , 251,000 and 374,000 common units, respectively, were issued upon exercise of options. During the year ended December 31, 2018 , 151,000 common units were issued upon the exercise of options. Equity Offering In September 2019, the Company completed the sale of 9.2 million common units, at a price of $50.50 per share, for net proceeds of $447.9 million . The net proceeds from this issuance were used to fund the early redemption on October 12, 2019 of the Operating Partnership's $350 million 4.75% senior notes due October 2020, repay outstanding balances on the Company's revolving credit facilities and for general corporate purposes. In conjunction with such early redemption, the Company incurred charges of approximately $9.0 million . Unit Repurchase The Company’s Board of Trustees had authorized a share repurchase plan under which the Company may purchase up to $250 million of the Company’s outstanding common units through September 28, 2019. Purchases made pursuant to the program may be made in either the open market or in privately negotiated transactions from time to time as permitted by securities laws and other legal requirements. There were no purchases under the plan during the three and nine months ended September 30, 2019 or for the year ended December 31, 2018.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	9 Months Ended
	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income	Accumulated Other Comprehensive Loss The following table sets forth the components of Accumulated Other Comprehensive Loss (in thousands): As of and for the nine months ended September 30, 2019 2018 Foreign Currency Translation: Beginning balance $ (52,862 ) $ (38,701 ) Translation adjustment (7,574 ) (9,221 ) Ending balance (60,436 ) (47,922 ) Derivative Instruments: Beginning balance (3,550 ) 150 Unrealized gain (1,820 ) 620 Reclassification adjustment (1) (67 ) (127 ) Ending balance (5,437 ) 643 Total accumulated other comprehensive loss (65,873 ) (47,279 ) Less: portion included in noncontrolling interest – operating partnership 1,377 957 Total accumulated other comprehensive loss included in shareholders' equity/owners' equity $ (64,496 ) $ (46,322 ) (1) Amounts reclassified out of Accumulated Other Comprehensive Loss/General & Limited Partner's Equity into contractual interest expense.

Real Estate

Real Estate	9 Months Ended
	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Real Estate	Real Estate Information on the Operating Properties and land parcels the Company acquired during the three months and nine months ended September 30, 2019 is as follows: Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 Number of Buildings Acres of Developable Land Leaseable Square Feet Purchase Price (in thousands) Number of Buildings Acres of Developable Land Leaseable Square Feet Purchase Price (in thousands) Chicago/Minneapolis — 23.5 — $ 13,200 — 23.5 — $ 13,200 Dallas — — — — 2 — 509,733 44,400 Southern California 1 — 203,280 55,500 2 — 492,963 86,785 United Kingdom — — — — — 25.0 — 2,658 Other: Atlanta — — — — — 154.7 — 5,000 New Jersey — — — — 3 — 488,254 78,275 1 23.5 203,280 $ 68,700 7 203.2 1,490,950 $ 230,318 In the nine months ended September 30, 2019, the Company purchased the noncontrolling interest of three consolidated joint ventures in the following reportable segments: four buildings in Philadelphia, one building in New Jersey, one building in Dallas and one building in Southern California as well as 21.7 acres of land in Arizona, for $18.5 million . Information on the Operating Properties and land parcels the Company sold during the three and nine months ended September 30, 2019 is as follows: Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 Number of Buildings Acres of Developable Land Leaseable Square Feet Gross Proceeds (in thousands) Number of Buildings Acres of Developable Land Leaseable Square Feet Gross Proceeds (in thousands) Carolinas/Richmond 1 — 136,000 $ 14,100 1 — 136,000 $ 14,100 Chicago/Minneapolis — — — — — 11.3 — 2,865 Florida — — — — 3 — 150,751 23,400 Houston — 7.6 — 1,700 — 11.6 — 3,205 Philadelphia 2 — 156,411 60,650 3 — 309,653 159,900 Other: Arizona — — — — — 8.8 — 11,500 New Jersey (1) — 67.6 — 4,070 — 68.4 — 8,070 DC Metro 1 — 290,762 92,500 2 — 437,234 154,250 Southeastern PA 2 — 180,151 30,000 5 18.0 254,331 40,200 6 75.2 763,324 $ 203,020 14 118.1 1,287,969 $ 417,490 (1) Includes land that the Company sold for $4.1 million to an unconsolidated joint venture in which the Company holds a 25% interest. In connection with the sale of a building in the Philadelphia reportable segment in June 2019 the Company repaid a $35.9 million 4.84% mortgage loan due 2033 encumbering the property and, consequently, recognized a loss of $7.6 million on early extinguishment of debt, which is reported in discontinued operations. In addition to the sale of land parcels described above, the Company also received gross proceeds of $5.5 million from the sale of non-depreciable assets in Tempe, Arizona included in Company’s Other reportable segment in the third quarter of 2019, as well as $4.0 million from the sale of non-depreciable assets in Camden, New Jersey included in the Company’s Philadelphia reportable segment during the nine months ended September 30, 2019. Including the above-described sales of land and other non-depreciable assets, the Company recognized gains on sales of non-depreciable assets of $7.0 million and $12.9 million during the three and nine months ended September 30, 2019, respectively. In addition to the transactions described above, during the three and nine months ended September 30, 2019, a subsidiary of the Company entered into an agreement with an entity affiliated with an employee of the Company, pursuant to which the Company waived its rights to purchase and develop a particular land parcel in Company’s Philadelphia reportable segment in consideration for reimbursement of a portion of the infrastructure costs totaling $3.2 million

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Segment Information	Segment Information The Company owns and operates industrial properties nationally and owns and operates certain non-core office properties in a focused group of office markets. Additionally, the Company owns certain assets in the United Kingdom. At September 30, 2019, the Company's reportable segments were based on the Company's method of internal reporting and were as follows: • Carolinas/Richmond; • Chicago/Minneapolis; • Cincinnati/Columbus/Indianapolis; • Dallas • Florida; • Houston; • Lehigh/Central PA; • Philadelphia; • Southern California; and • United Kingdom. Certain other segments are aggregated into an "Other" category which includes the reportable segments: Arizona; Atlanta; DC Metro; New Jersey; and Southeastern Pennsylvania. Comparative prior periods have been restated to reflect current segment disclosures. 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): Three Months Ended Nine Months Ended September 30, 2019 September 30, 2018 September 30, 2019 September 30, 2018 Revenue Carolinas/Richmond $ 20,377 $ 19,417 $ 61,129 $ 58,723 Chicago/Minneapolis 17,479 17,274 52,299 50,414 Cincinnati/Columbus/Indianapolis 4,792 4,245 13,822 13,613 Dallas 5,953 5,537 17,252 14,300 Florida 15,871 15,847 48,218 47,117 Houston 19,103 16,561 51,831 48,514 Lehigh/Central PA 38,878 39,188 118,588 115,799 Philadelphia 9,779 10,598 32,043 33,659 Southern California 10,510 7,914 30,660 22,226 United Kingdom 5,900 3,523 17,857 11,579 Other 22,768 32,119 69,717 97,853 Segment-level revenue 171,410 172,223 513,416 513,797 Reconciliation to total revenue Development service fee income 257 12,956 2,099 59,132 Discontinued operations (8,498 ) (23,911 ) (33,593 ) (73,613 ) Other — 18 (179 ) (372 ) Total revenue $ 163,169 $ 161,286 $ 481,743 $ 498,944 Net operating income Carolinas/Richmond $ 15,638 $ 14,620 $ 47,020 $ 43,795 Chicago/Minneapolis 10,902 10,564 33,294 31,271 Cincinnati/Columbus/Indianapolis 3,262 2,749 9,186 9,099 Dallas 4,035 3,666 11,848 9,274 Florida 11,628 11,461 35,097 33,717 Houston 12,377 9,676 32,159 28,714 Lehigh/Central PA 29,902 29,406 89,639 86,085 Philadelphia 7,876 7,947 25,583 28,211 Southern California 8,200 6,496 23,524 17,675 United Kingdom 5,421 3,234 16,131 10,662 Other 15,507 23,213 47,727 69,620 Net operating income 124,748 123,032 371,208 368,123 Reconciliation to income from continuing operations Interest expense (1) (26,220 ) (24,670 ) (78,297 ) (71,331 ) Development service fee income 257 12,956 2,099 59,132 Development service fee expense (168 ) (12,924 ) (1,848 ) (120,799 ) Depreciation/amortization expense (1) (2) (32,279 ) (32,243 ) (97,642 ) (97,576 ) Impairment charges - real estate assets — — (99 ) (26,000 ) Gain on property dispositions 15,168 2,002 21,125 54,705 Equity in earnings of unconsolidated joint ventures 1,776 6,766 10,966 20,958 General and administrative expense (1) (10,193 ) (9,814 ) (35,559 ) (32,758 ) Leasing cost (3,082 ) (2,610 ) (9,608 ) (8,189 ) Other operating expenses (3,166 ) (3,169 ) (8,690 ) (7,467 ) Discontinued operations excluding losses on impairment and debt extinguishment and gain on property dispositions (4,951 ) (14,320 ) (18,553 ) (39,842 ) Income taxes (1) (2) (811 ) (329 ) (1,635 ) (1,539 ) Other (592 ) 196 1,389 (3,262 ) Income from continuing operations $ 60,487 $ 44,873 $ 154,856 $ 94,155 (1) Includes activity in discontinued operations. (2) Excludes costs that are included in determining net operating income. The Company's total assets by reportable segment as of September 30, 2019 and December 31, 2018 is as follows (in thousands): September 30, 2019 December 31, 2018 Carolinas/Richmond $ 516,811 $ 525,041 Chicago/Minnesota 597,557 591,792 Cincinnati/Columbus/Indianapolis 134,111 131,400 Dallas 306,463 261,538 Florida 550,623 547,232 Houston 608,761 568,756 Lehigh/Central PA 1,225,016 1,210,220 Philadelphia 540,972 624,373 Southern California 766,578 660,688 United Kingdom 392,091 463,162 Other 1,062,447 1,153,518 Segment-level total assets 6,701,430 6,737,720 Corporate Other 637,302 196,674 Total assets $ 7,338,732 $ 6,934,394

Impairment and Disposal of Long

Impairment and Disposal of Long-Lived Assets	9 Months Ended
	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Impairment and Disposal of Long-Lived Assets	7 : Impairment or Disposal of Long-Lived Assets In 2017, the Company initiated a strategic shift whereby it adopted a plan to divest of its remaining suburban office properties. In the third quarter of 2018, the Company updated its strategy whereby it adopted a plan to divest of all of its remaining office properties. The Company determined that the strategic shift would have a major effect on its operations and financial results. As such, properties sold or those that meet the criteria to be classified as held for sale within the corporate strategy were classified within discontinued operations. Consistent with the held for sale criteria these properties are expected to be sold within one year . As a result of the classification within discontinued operations, the in-service assets and liabilities of this portfolio are required to be presented as held for sale for all prior periods presented in our Consolidated Balance Sheets. Operating results pertaining to these properties were reclassified to discontinued operations for all prior periods presented in our Consolidated Statements of Comprehensive Income. The following table illustrates the number of sold or held for sale properties included in, or excluded from, discontinued operations: Held for sale as of September 30, 2019 Sold during the nine months ended September 30, 2019 Sold during the year ended December 31, 2018 Total Properties included in discontinued operations 9 13 37 59 Properties included in continuing operations 1 1 2 4 Properties sold or classified as held for sale 10 14 39 63 In addition, there were three land parcels comprising 74.4 acres included as held for sale as of September 30, 2019. The properties held for sale with operating results in discontinued operations as of September 30, 2019 were located in the following reportable segments: one property in Chicago/Minneapolis, six properties in Philadelphia and two properties in the United Kingdom. A summary of the results of operations for the properties classified as discontinued operations is as follows (in thousands): Three Months Ended Nine Months Ended September 30, 2019 September 30, 2018 September 30, 2019 September 30, 2018 Revenues $ 8,498 $ 23,911 $ 33,593 $ 73,613 Operating expenses (3,117 ) (5,329 ) (10,903 ) (17,276 ) Depreciation and amortization — (2,666 ) (2,129 ) (11,138 ) Impairment charges - real estate assets (7,190 ) — (21,482 ) — Interest and other income (expense) 4 (31 ) (57 ) (132 ) Income taxes (5 ) (28 ) (298 ) (83 ) Loss on debt extinguishment — — (7,618 ) — Interest expense (429 ) (1,537 ) (1,653 ) (5,142 ) Gain on property dispositions 44,428 94,878 116,452 184,689 Income from discontinued operations 42,189 109,198 105,905 224,531 Noncontrolling interest - operating partnership (916 ) (2,544 ) (2,404 ) (5,232 ) Noncontrolling interest - consolidated joint venture — (224 ) (186 ) (412 ) Income from discontinued operations available to common shareholders $ 41,273 $ 106,430 $ 103,315 $ 218,887 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 included in discontinued operations to the sum of total net assets plus consolidated debt. Capital expenditures on a cash basis related to properties within discontinued operations were $0.1 million and $3.6 million , respectively, for the three and nine months ended September 30, 2019, and $10.8 million and $38.3 million , respectively, for the three and nine months ended September 30, 2018. Assets Held for Sale As of September 30, 2019 , 10 properties were classified as held for sale, of which nine properties met the criteria to be classified within discontinued operations and one property was classified within continuing operations. In addition, there were three land parcels comprising 74.4 acres included as held for sale as of September 30, 2019. The following table illustrates aggregate balance sheet information for all held for sale properties (in thousands): September 30, 2019 December 31, 2018 Included in Continuing Operations Included in Discontinued Operations Total Included in Continuing Operations Included in Discontinued Operations Total Land and land improvements $ 613 $ 19,210 $ 19,823 $ 1,301 $ 113,080 $ 114,381 Buildings and improvements 8,541 174,595 183,136 5,638 384,737 390,375 Development in progress — 10,108 10,108 — 9,597 9,597 Land held for development 19,420 — 19,420 26,253 — 26,253 Accumulated depreciation (3,745 ) (21,592 ) (25,337 ) (1,546 ) (70,242 ) (71,788 ) Deferred financing and leasing costs, net 717 7,910 8,627 58 13,697 13,755 Other assets 756 9,971 10,727 164 19,470 19,634 Total assets held for sale $ 26,302 $ 200,202 $ 226,504 $ 31,868 $ 470,339 $ 502,207 Total liabilities held for sale $ 419 $ 15,520 $ 15,939 $ 141 $ 20,990 $ 21,131 Impairment Charges - Real Estate Assets The Company recorded $7.2 million and $21.6 million of impairment charges during the three and nine months ended September 30, 2019 , respectively. These impairment charges were primarily related to an office building in the Company's DC Metro segment that was sold in the three months ended September 30, 2019 and is primarily included in discontinued operations in the Company's Consolidated Statements of Comprehensive Income. The Company determined these impairments based on third party offer prices which are Level 2 according to the fair value hierarchy established in ASC 820. The Company recorded a $26.0 million impairment charge during the nine months ended September 30, 2018. This charge related to the Camden Waterfront project located in Camden, New Jersey and reported in the Company's Philadelphia reportable segment. The Company determined this impairment based on quoted offer prices on comparable properties, which is a Level 3 fair value calculation. The Company has applied reasonable estimates and judgments in evaluating each of its properties and land held for development and has determined that there are no additional valuation adjustments necessary at September 30, 2019 . Should external or internal circumstances change requiring the need to shorten the holding periods or adjust the estimated future cash flows of the Company’s assets, the Company could be required to record additional impairment charges in the future.

Noncontrolling Interests of the

Noncontrolling Interests of the Trust	9 Months Ended
	Sep. 30, 2019
Stockholders' Equity Attributable to Noncontrolling Interest [Abstract]
Noncontrolling Interests of the Trust	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 of the Operating Partnership not held by the Trust outstanding as of September 30, 2019 have the same economic characteristics as common shares of the Trust. The 3.5 million outstanding common units of the Operating Partnership 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 3.5 million outstanding common units based on the closing price of the common shares of the Trust at September 30, 2019 was $ 179.3 million .

Limited Partners' Equity and No

Limited Partners' Equity and Noncontrolling Interest of the Operating Partnership	9 Months Ended
	Sep. 30, 2019
Preferred Units [Line Items]
Limited Partners' Equity and Noncontrolling Interest of the Operating Partnership	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 of the Operating Partnership not held by the Trust outstanding as of September 30, 2019 have the same economic characteristics as common shares of the Trust. The 3.5 million outstanding common units of the Operating Partnership 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 3.5 million outstanding common units based on the closing price of the common shares of the Trust at September 30, 2019 was $ 179.3 million .
Liberty Property Limited Partnership
Preferred Units [Line Items]
Limited Partners' Equity and Noncontrolling Interest of the Operating Partnership	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 have the same economic characteristics as common shares of the Trust. The 3.5 million outstanding common units as of September 30, 2019 not held by the Trust are the limited partners' equity - common units held by persons and entities other than the Trust. 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 3.5 million outstanding common units based on the closing price of the common shares of the Trust at September 30, 2019 was $ 179.3 million .

Noncontrolling Interest - Opera

Noncontrolling Interest - Operating Partnership/Limited Partnership/Limited Partners' Equity - Preferred Units	9 Months Ended
	Sep. 30, 2019
Temporary Equity [Line Items]
Noncontrolling Interest - Operating Partnership/Limited Partnership/Limited Partners' Equity - Preferred Units	Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units As of September 30, 2019 , the Company had outstanding the following cumulative preferred units of the Operating Partnership: ISSUE AMOUNT UNITS LIQUIDATION PREFERENCE DIVIDEND RATE (in 000’s) Series I-2 $ 5,337 213 $ 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. During the nine months ended September 30, 2019, 88,000 preferred units were redeemed for $2.2 million

Indebtedness

Indebtedness	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Indebtedness	Indebtedness In January 2019, the Company issued $350 million of 4.375% senior unsecured notes due 2029. The net proceeds from this issuance were used to repay borrowings under the Company's unsecured credit facilities and for general corporate purposes.

Disclosure of Fair Value of Fin

Disclosure of Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2019
Debt Instrument, Fair Value Disclosure [Abstract]
Disclosure of Fair Value of Financial Instruments	Fair Value of Financial Instruments ASC 820, Fair Value Measurements and Disclosures , provides guidance on the fair value measurement of a financial asset or liability. Inputs used to develop fair value are classified in one of three categories: Level 1 inputs (quoted prices (unadjusted) in active markets for identical assets or liabilities), Level 2 inputs (inputs other than quoted prices that are observable for the asset or liability, either directly or indirectly) and Level 3 inputs (unobservable inputs for the asset or liability). 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 December 31, 2018 and September 30, 2019 . The use of different market assumptions and/or estimation methodologies may have a material effect on the estimated fair value amounts. The carrying value of cash and cash equivalents, restricted cash, accounts receivable, accounts payable, accrued interest, dividend and distributions payable and other liabilities are reasonable estimates of fair value because of the short-term nature of these instruments. The carrying value of the outstanding amounts under the Company's credit facilities is a reasonable estimate of fair value because interest rates float at a rate based on LIBOR. The Company determines the fair value of its interest rate swaps by using the standard methodology of netting discounted future fixed cash payments with the discounted expected variable cash receipts. These variable cash receipts of interest rate swaps are based on expectations of future LIBOR interest rates (forward curves) estimated by observing market LIBOR interest rate curves. This is a Level 2 fair value calculation. Also, credit valuation adjustments are factored into the fair value calculations to account for potential nonperformance risk. These credit valuation adjustments were concluded to not be significant inputs for the fair value calculations for the periods presented. See Note 14 - Derivative Instruments. The Company used a discounted cash flow model to determine the estimated fair value of its debt as of December 31, 2018 and September 30, 2019 . 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, 2018 and September 30, 2019 (in thousands): Mortgage Loans Unsecured Notes Carrying Value Fair Value Carrying Value Fair Value As of December 31, 2018 $ 395,202 $ 397,167 $ 2,285,698 $ 2,295,699 As of September 30, 2019 $ 297,326 $ 304,689 $ 2,633,941 $ 2,821,931

Unconsolidated Joint Ventures

Unconsolidated Joint Ventures	9 Months Ended
	Sep. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Unconsolidated Joint Ventures	Unconsolidated Joint Ventures Liberty Property 18th & Arch LP and Liberty Property 18th & Arch Hotel, LP On June 30, 2014, the Company entered into two joint ventures for the purpose of developing and owning the Comcast Technology Center (the “Project”) located in Philadelphia, Pennsylvania as part of a mixed-use development. The 60 -story building includes 1.3 million square feet of leasable office space (the “Office”), which is substantially complete and fully occupied by Comcast Corporation, and a 219 -room Four Seasons Hotel (the “Hotel”), which is substantially complete and opened to the public in August 2019. Costs for the development of the Project, exclusive of tenant-funded interior improvements, are anticipated to be approximately $968 million . As of September 30, 2019, the Company's investment in the project was $193.7 million and is reflected in investments in and advances to unconsolidated joint ventures in the Company's consolidated balance sheet. These joint ventures are part of the Company's Philadelphia reportable segment. The two joint ventures engaged the Company as the developer of the Project pursuant to a Development Agreement by which the Company agreed, 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 as well as the payment, subject to certain exceptions, of any cost overruns incurred in the development of the Project. To mitigate its risk, the Company entered into guaranteed maximum price contracts (the "GMP Contracts") with a third party contractor (the "General Contractor") to construct the Project. The Company has been notified by the General Contractor that the General Contractor has incurred cost overruns comprised of amounts owed to third-party subcontractors and internal general condition costs of the General Contractor in connection with completing the Project in excess of the guaranteed maximum price payable to the General Contractor under the GMP Contracts, which guaranteed maximum price has been previously adjusted pursuant to accepted change orders. Notwithstanding the GMP Contracts, the General Contractor has generally refused to fund the cost overruns owed to third-party subcontractors, and the Company has funded, and may continue to fund, subcontractor cost overruns in compliance with its obligations under its development cost guarantee to the joint ventures. Accordingly, in periods prior to 2019, the Company accrued $69.3 million relating primarily to cost overruns that it estimated were probable of being funded to third-party subcontractors under its development cost guarantees to the joint ventures. As of September 30, 2019 and December 31, 2018, the Company's remaining accrual was $29.6 million and $67.3 million , respectively (including, in each case, estimated retainage of approximately $24 million payable to subcontractors), which accruals are included in other liabilities in the accompanying consolidated balance sheets and are reflective of amounts cumulatively funded by the Company as of those dates. The Company is accounting for the development of the Project on a variable basis as a percentage of costs incurred under the development contract. The Company recognized a loss of $61.8 million for the nine months ended September 30, 2018 in development service fee income, net of development service fee expense and other related expenses. There was no loss or gain recognized related to the Project during the three months ended September 30, 2018 or the three and nine months ended September 30, 2019. The Company intends to pursue all remedies to recover from the General Contractor any amounts expended by the Company or the joint ventures in excess of their contractual obligations. In addition to the costs to comply with the Company's obligations under its development cost guarantee, other claims related to the development of the Project have been asserted by the General Contractor and certain subcontractors. Should disputes with respect to these asserted claims proceed, the Company expects that it would assert claims against the General Contractor, both with respect to the claims as to which the above-described accrual has been made, as well as with respect to the additional claims described in this paragraph. There can be no assurances that amounts incurred, including as a result of such claims, will not exceed the above estimates. The Company is not able to reasonably estimate the amount of additional costs, if any, that it may incur as a result of such claims, and accordingly any potential exposure of the Company for such claims is not included within the accrual described above. Similarly, the Company is not able to reasonably estimate the amount, if any, that the Company may recover with respect to any claims it may assert against the General Contractor. If the Company were to incur additional expenses in connection with its development cost guarantee or in connection with such claims, such amounts would be accrued when they are determined to be probable of being incurred and are reasonably estimable, and could be material to the Company's results of operations in future periods. If the Company were to subsequently recover any of the cost overruns initially funded by the Company, whether pursuant to any such claims asserted by the Company or otherwise, such recoveries would be recorded when and if realized in future periods. Liberty Washington, LP During the three months ended September 30, 2019, the Company concluded that a property owned by this joint venture and held for sale had an indicator of impairment resulting from a decline in the Washington, DC market fundamentals. The joint venture recognized impairment charges of $10.3 million and $26.7 million for the three and nine months ended September 30, 2019, respectively. The Company's share of these impairment charges were $2.6 million and $6.7 million , respectively, for the same periods. The impairment charges are related to the Company's DC Metro reportable segment and the Company's share is included in equity in earnings of unconsolidated joint ventures in the accompanying consolidated statements of comprehensive income. The Company determined these impairments based on estimated future discounted cash flows. This is a Level 3 fair value calculation. Cambridge Medipark Ltd During the three and nine months ended September 30, 2019 , Cambridge Medipark, Ltd (a joint venture in which the Company holds a 50% interest) recognized gains on the sale of land leasehold interests. The Company's share of these gains was $112,000 and $1.1 million for the three and nine months ended September 30, 2019, respectively, compared to $1.2 million and $5.0 million

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments The Company borrows funds at a combination of fixed and variable rates. Borrowings under the Company's revolving credit facility and certain bank mortgage loans bear interest at variable rates. Other long-term debt typically bears interest at fixed rates. The Company's interest rate risk management objectives are to limit generally the impact of interest rate changes on earnings and cash flows and to lower the Company's overall borrowing costs. To achieve these objectives, from time to time, the Company enters 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. The Company generally does not hold or issue these derivative contracts for trading or speculative purposes. 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 changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive loss and noncontrolling interest (for the Trust) and general partner's equity and limited partners ’ equity - common units (for the Operating Partnership) and is subsequently reclassified into interest expense in the period that the hedged forecasted transaction affects earnings. The Company determines the fair value of its interest rate swaps by netting discounted future fixed cash payments with the discounted expected variable cash receipts. These variable cash receipts of interest rate swaps are based on expectations of future LIBOR interest rates (forward curves) estimated by observing market LIBOR interest rate curves. This is a Level 2 fair value calculation. Also, credit valuation adjustments are factored into the fair value calculations to account for potential nonperformance risk. These credit valuation adjustments were concluded to be not significant inputs for the fair value calculations for the periods presented. The Company holds an interest in two interest rate swap contracts (“Swaps”) that eliminate the impact of changes in interest rates on the payments required under variable rate mortgages. The Swaps had aggregate notional amounts of $65.1 million and $66.8 million at September 30, 2019 and December 31, 2018 , respectively, and expire in 2020 . In addition, in late 2018, in anticipation of conducting the offering of senior notes described in Note 11, the Operating Partnership entered into two interest rate lock agreements tied to the U.S. treasury rate for an aggregate notional amount of $200 million . An interest rate lock is a tool used to manage interest-rate risk by effectively securing interest rates on federal government securities as of the agreement date. One agreement had a notional amount of $100 million and was settled in 2018 for $2.4 million . The second agreement had a notional amount of $100 million and was settled in 2019 for $3.3 million . The interest rate lock agreements qualified as cash flow hedges with respect to the senior notes offering and, as such, the settlements of $5.7 million are being amortized into interest expense over the respective term of the notes. The Company accounts for the changes in the fair value of a derivative in accumulated other comprehensive loss and subsequently reclassifies amounts to earnings over the term that the hedged transaction affects earnings. The following table presents the location in the financial statements of the gains or losses recognized related to the Company’s cash flow hedges for the three and nine months ended September 30, 2019 and 2018 (in thousands): Three Months Ended Nine Months Ended September 30, 2019 September 30, 2018 September 30, 2019 September 30, 2018 Amount of gain related to the effective portion recognized in other comprehensive (loss) income $ 13 $ 69 $ 424 $ 619 Total Amount of Interest Expense Presented in the Consolidated Statements of Comprehensive Income 25,791 23,133 76,644 66,189 The following table presents the fair value of the Company’s derivative financial instruments as well as their classification on the accompanying consolidated balance sheets as of September 30, 2019 and December 31, 2018 (amounts in thousands): Derivatives Fair Value at: Balance Sheet Location September 30, 2019 December 31, 2018 Derivatives designated as hedging instruments: Interest Rate Swaps Other Liabilities $ 345 $ 677 Interest Rate Treasury Locks Other Liabilities — 3,972 Total $ 345 $ 4,649 Amounts reported in accumulated other comprehensive income related to derivatives will be reclassified to interest expense as interest payments are made on the Company’s debt. The Company estimates that $0.5 million will be reclassified from accumulated other comprehensive loss as an increase to interest expense over the next 12 months. The Company has agreements with its derivative counterparties that contain a provision whereby if the Company defaults on any of its indebtedness, including defaults where repayment of the indebtedness has not been accelerated by the lender, then the Company could also be declared in default on its derivative obligations. If the Company were to breach any of the contractual provisions of the derivative contracts, it would be required to settle its obligations under the agreements at their termination value including accrued interest, which totaled approximately $0.3 million as of September 30, 2019 .

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Environmental Matters Substantially all of the Company's properties and land were subject to Phase I Environmental Assessments and when appropriate Phase II Environmental Assessments (collectively, the “Environmental Assessments”) obtained in contemplation of their acquisition by the Company or obtained by predecessor owners prior to the sale of the property or land to the Company. The Environmental Assessments did not reveal, nor is the Company aware of, any non-compliance with environmental laws, environmental liability or other environmental claim that the Company believes would likely have a material adverse effect on the Company. 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 September 30, 2019 there were no legal proceedings, claims or assessments that the Company expects to have a material adverse effect on the Company. However, see Note 13 for discussion of Comcast Technology Center. Other As of September 30, 2019 , the Company had letter of credit obligations of $8.9 million . As of September 30, 2019 , the Company had 22 buildings under development. These buildings are expected to contain, when completed, a total of 4.7 million square feet of leasable space and represent an anticipated aggregate investment of $463.9 million . At September 30, 2019 , development in progress totaled $323.8 million . In addition, as of September 30, 2019 , the Company had invested $3.2 million in deferred leasing costs related to these development buildings. The Company is also currently developing three properties for its unconsolidated joint ventures which represent an anticipated aggregate investment by the joint ventures of $ 35.6 million . As of September 30, 2019, the Company was committed to the following: • $20.3 million in improvements on certain buildings and land parcels; • $53.1 million in future land acquisitions which it expects to complete during the year ending December 31, 2019; • up to $19.5 million of tenant improvements not yet completed; and • infrastructure improvements of approximately $1.0 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. Two unconsolidated joint ventures in which the Company holds an interest have engaged the Company as the developer of the Comcast Technology Center (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 as well as the payment, subject to certain exceptions, of any cost overruns incurred in the development of the Project. See Note 13 for details on the commitments and contingencies associated with the Project.

Supplemental Disclosure to Stat

Supplemental Disclosure to Statements of Cash Flows	9 Months Ended
	Sep. 30, 2019
Supplemental Cash Flow Information [Abstract]
Supplemental Disclosure to Statements of Cash Flows	Supplemental Disclosure to Consolidated Statements of Cash Flows The following are supplemental disclosures to the consolidated statements of cash flows for the nine months ended September 30, 2019 and 2018 (amounts in thousands): 2019 2018 Write-off of fully depreciated/amortized property and deferred costs - properties included in continuing operations $ 2,218 $ 7,197 Write-off of fully depreciated/amortized property and deferred costs - properties included in discontinued operations $ — $ 11,789 Write-off of depreciated property and deferred costs due to sale/demolition - properties included in continuing operations $ 1,642 $ 20,273 Write-off of depreciated property and deferred costs due to sale and related debt repayment - properties included in discontinued operations $ 51,455 $ 99,072 Changes in accrued development capital expenditures - properties included in continuing operations $ (4,436 ) $ 12,361 Changes in accrued development capital expenditures - properties included in discontinued operations $ — $ (4,628 ) Unrealized (loss) gain on cash flow hedge $ (1,887 ) $ 493 Capitalized equity-based compensation $ 915 $ 727 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. The following is a reconciliation of the Company's cash and cash equivalents and restricted cash at the beginning and end of the nine months ended September 30, 2019 and 2018 (amounts in thousands): 2019 2018 Cash and cash equivalents at beginning of period $ 84,923 $ 11,882 Restricted cash at beginning of period 10,899 13,803 Cash and cash equivalents and restricted cash at beginning of period $ 95,822 $ 25,685 Cash and cash equivalents at end of period $ 514,882 $ 17,770 Restricted cash at end of period 14,006 13,371 Cash and cash equivalents and restricted cash at end of period $ 528,888 $ 31,141 Restricted cash includes tenant security deposits and escrow funds that the Company maintains pursuant to certain mortgage loans. Restricted cash also includes the undistributed proceeds from the sale of land in Kent County, United Kingdom.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2019
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent Events Prepayment of Senior Notes On October 12, 2019, the Company prepaid the Operating Partnership's $350 million 4.75% unsecured notes due in October 2020. The Company incurred a loss on early extinguishment of debt of approximately $9.0 million . Proposed Merger with Prologis, Inc. On October 27, 2019, the Trust, Leaf Holdco Company Trust, a Maryland real estate investment trust and wholly owned subsidiary of the Trust (“New Liberty Holdco”), and the Operating Partnership (collectively with the Trust and New Liberty Holdco, the “Company Parties”), entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Prologis, Inc., a Maryland corporation (“Prologis”), Lambda REIT Acquisition LLC, a Maryland limited liability company and wholly owned subsidiary of Prologis (“Prologis Merger Sub”), Prologis, L.P., a Delaware limited partnership (“Prologis OP”), and Lambda OP Acquisition LLC, a Delaware limited liability company and wholly owned subsidiary of Prologis OP (“Prologis OP Merger Sub” and, together with Prologis, Prologis Merger Sub and Prologis OP, the “Prologis Parties”). The Merger Agreement provides that upon the terms and subject to the conditions set forth in the Merger Agreement, (i) a newly created indirect wholly owned subsidiary of New Liberty Holdco will merge with and into the Trust (the “Company Merger”) with the Trust continuing as the surviving entity and as an indirect wholly owned subsidiary of New Liberty Holdco; (ii) thereafter, New Liberty Holdco will merge with and into Prologis Merger Sub (the “Topco Merger” and together with the Company Merger, the “Company Mergers”), with Prologis Merger Sub continuing as the surviving corporation and a wholly owned subsidiary of Prologis; (iii) immediately after the Topco Merger, Prologis will cause all of the outstanding equity interests in the Prologis Merger Sub to be contributed to Prologis OP in exchange for the issuance by Prologis OP of partnership interests in Prologis OP to other subsidiaries of Prologis; and (iv) thereafter, Prologis OP Merger Sub will merge with and into the Operating Partnership, with the Operating Partnership continuing as the surviving entity and a wholly owned subsidiary of Prologis OP (the “Partnership Merger” and together with the Company Merger and the Topco Merger, the “Mergers”). Under the terms of the Merger Agreement, shareholders of the Trust and holders of common units in the Operating Partnership will receive 0.675 shares of Prologis common stock and limited partnership interests in Prologis OP, respectively, for each common share of the Trust or common unit in the Operating Partnership that they own. The board of trustees of the Trust and the board of directors of Prologis have both unanimously approved the Merger Agreement, the Mergers and the other transactions contemplated by the Merger Agreement. The transaction, which is currently expected to close in the first quarter of 2020, is subject to the approval of the Trust’s shareholders and other customary closing conditions.

Organization and Basis of Pre_2

Organization and Basis of Presentation (Policy)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Recently Issued Accounting Standards	Revenue Recognition In May 2014, the Financial Accounting Standards Board (“FASB”) issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which supersedes nearly all existing revenue recognition guidance (except revenue in the scope of other accounting standards, including standards related to leasing). Subsequently, the FASB issued supplementary standards providing additional guidance and targeted improvements to ASU 2014-09 (collectively, the “Revenue Standards”). The Revenue Standards provide a unified model to determine how revenue is recognized. In accordance with the Revenue Standards, the Company performs the following steps: (i) identify the contract with the customer, (ii) identify the performance obligations within the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations and (v) recognize revenue when (or as) a performance obligation is satisfied. Upon adoption of the Revenue Standards, the Company evaluated each of its revenue streams: lease agreement revenue, development service fee revenue, deferred land sale revenue and gain or loss on sale of nonfinancial assets. The Company concluded that there are no revenue streams from its lease agreements that are covered by the Revenue Standards with the possible exception of non-lease components as further discussed below. The Revenue Standards did not have an impact on the amount and timing of recognizing the Company's development service fee income. The Company recognizes development service fee income on a variable basis as a percentage of costs incurred on third party development contracts. Property development services, which are a single performance obligation, continue to be satisfied and recognized over time. The Company measures its progress toward completing the performance obligations under each arrangement. The measurement of the transfer of value to the customer for these services utilizes the input method (actual costs incurred against anticipated project costs) since this method best depicts the actual transfer of value promised to the customer. Estimated expected losses on such contracts are accrued in the period in which they are determinable. The total amount of consideration to be received from these projects is assessed on a quarterly basis. Based on existing contracts, substantial completion is anticipated during 2020. The Company recognizes revenues from improving land sites and selling the underlying land on behalf of its development partner to home builders in the United Kingdom. These agreements typically contain a pre-emption clause and a seller's call option. The Company recognizes revenue as the pre-emption period or seller's call option lapses utilizing the output method. There was $4.5 million and $10.4 million in revenue recognized for such contracts during the three and nine months ended September 30, 2019, respectively. The Revenue Standards did not have an impact on the gain or loss on sale of nonfinancial assets. The Revenue Standards require the Company to derecognize nonfinancial assets once it transfers control of a distinct nonfinancial asset or distinct in-substance nonfinancial asset. Additionally, when the Company transfers its controlling interest in a nonfinancial asset, but retains a noncontrolling ownership interest, the Company is required to measure any noncontrolling interest it receives or retains at fair value. The guidance requires companies to recognize a full gain or loss on the transaction. See Notes 5 and 7 for further discussion of sales of nonfinancial assets during the nine months ended September 30, 2019. Estimated gross revenue related to the remaining performance obligations under existing contracts (before allocation of related costs and expenses) as of September 30, 2019 that will be recognized as revenue in future periods was approximately $28.1 million , which is expected to be recognized in 2019 through 2022. Recently Issued Accounting Standards Leases In February 2016, the FASB issued Accounting Standard Update 2016-02, Leases (“ASU 2016-02”). Additional guidance and targeted improvements to ASU 2016-02 were made through the issuances of supplementary ASUs in July 2018, December 2018 and March 2019 (collectively, the "New Lease Standard"). The New Lease Standard sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). It requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase of the leased asset by the lessee. This classification will determine whether the lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. The New Lease Standard requires lessors to account for leases using an approach that is substantially equivalent to prior guidance for sales type leases, direct financing leases and operating leases. The New Lease Standards limit capitalization of certain initial direct costs which were capitalizable under previous lease standards. Such costs, which were expensed during the three and nine months ended September 30, 2019, were $0.1 million and $0.7 million , respectively. The Company adopted the New Lease Standard on January 1, 2019 and applied it using a modified retrospective approach whereby the cumulative effect of the adoption was recognized on the adoption date and prior periods were not restated. There was no net cumulative effect adjustment to retained earnings as of January 1, 2019 as a result of this adoption. The following practical expedients available for implementation were elected: a. whether an expired or existing contract meets the definition of a lease b. the lease classification at the adoption date for existing or expired leases c. whether costs previously capitalized as initial direct costs would continue to be amortized Additionally, the Company has elected the practical expedient not to recognize right of use assets and lease liabilities with a term of one year or less. The Company's leases met the criteria in the New Lease Standard to not separate non-lease components from the related lease component; therefore, the accounting for these leases remained largely unchanged from the previous standard. The Company has elected to exclude sales and other similar taxes from the measurement of lease revenue and expense and the Company has excluded those costs paid directly by lessees to third parties. Lessee Disclosure As of September 30, 2019, the Company had a total of five properties subject to operating ground leases in Florida, New Jersey, Kentucky and the United Kingdom with a weighted average remaining term of 47 years. These leases have remaining terms of 11 to 110 years, expiration dates of June 2030 to June 2129, and renewal options of 25 to 48 years. The Company has included in the lease terms renewal options up to the useful life of the asset constructed on the land. Payments for certain properties are subject to increases at five year intervals based upon the agreed or appraised fair market value of the leased premises on the adjustment date or the Consumer Price Index percentage increase since the base rent date. These future changes in payments are considered variable payments and do not impact the assessment of the asset or liability unless there is a significant event that triggers reassessment, such as an amendment with a change in the terms of the lease. The Company used discount rates in a range of 4.1% to 5.0% for a weighted average discount rate of 4.6% , which was derived from the Company's assessment of credit quality of the Company adjusted to reflect secured borrowing, estimated yield curves and long-term spread adjustments over appropriate tenures. The Company also leases office space from unrelated third-parties. The Company recognized lease expense of $0.5 million and $1.5 million during the three and nine months ended September 30, 2019, respectively, of which $0.5 million and $1.4 million , respectively, was paid in cash. The following schedule indicates the approximate future minimum lease payments for the ground and office leases as of September 30, 2019: Year Amount (in thousands) 2019 (remainder of year) $ 373 2020 1,370 2021 1,234 2022 1,136 2023 1,035 Thereafter 40,684 Total minimum payments $ 45,832 Imputed interest (26,941 ) Amortization (512 ) Lease liabilities $ 18,379 Deferred rent (715 ) Right of use asset $ 17,664 As noted above, the Company adopted the New Lease Standard effective January 1, 2019. Since the Company has applied the provisions on a modified retrospective basis, the following represents approximate future minimum lease payments by year as of December 31, 2018, as applicable under ASC 840, Leases, prior to the adoption of the New Lease Standard. Year Amount (in thousands) 2019 $ 1,512 2020 1,356 2021 1,205 2022 1,082 2023 981 Thereafter 40,799 $ 46,935 The Company recorded ground lease expense of $1.5 million for the year ended December 31, 2018. Lessor Disclosures The Company leases its operating properties to customers under agreements that are classified as operating leases. It manages residual risk through investing in properties that it believes will appreciate in value over time. Substantially all of the Company's operating leases contain provisions for specified annual increases over the rents of the prior year. Rental income from operating leases is generally recognized on a straight-line basis over the lease term when the Company has determined that the collectibility of substantially all the lease payments is probable. If the Company determines that it is not probable that substantially all of the lease payments will be collected, the Company accounts for the revenue under the lease on a cash basis. Changes in the assessment of probability are accounted for on a cumulative basis as if the lease had always been accounted for based on the current determination of the likelihood of collection potentially resulting in increased volatility of rental revenue. Some of the Company's leases have options to extend, terminate or purchase the facilities, which are considered when determining the lease term. Tenant rights to purchase an underlying asset are typically at prevailing market rates at the time of purchase. The Company does not include in the measurement of lease receivables certain variable payments, including changes in an index, until the specific events that trigger the variable payments have occurred. Generally operating leases require the tenants to reimburse the Company for property tax and other expenditures that are not considered components of the lease and therefore no consideration is allocated to them as they do not result in the transfer of a good or service to the tenants. The Company has determined that all of its leases qualify for the practical expedient to not separate the lease and non-lease components because (i) the lease components are operating leases and (ii) the timing and pattern of recognition of the non-lease components are the same as the lease components. The Company applies the New Lease Standard to the combined component. Income derived from the Company's leases is recorded in rental revenue in the Company's consolidated statements of comprehensive income. Certain tenants are obligated to pay directly their obligations under their leases for real estate taxes, insurance and certain other expenses. These obligations, which have been assumed by the tenants under the terms of their respective leases, are not reflected in the Company's consolidated financial statements. To the extent any tenant responsible for these obligations under the respective lease defaults on its lease or if it is deemed probable that the tenant will fail to pay for such costs, the Company would record a liability for such obligation. The following details the rental income and variable lease income for the three and nine months ended September 30, 2019 (in thousands): Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Rental income - operating leases - continuing operations $ 127,125 $ 371,744 Rental income - operating leases - discontinued operations 6,233 25,481 Variable lease income - operating leases - continuing operations 35,787 107,900 Variable lease income - operating leases - discontinued operations 2,265 8,112 The following amounts reflect the estimated contractual rents due to the Company for the remainder of terms of the Company's operating leases as of September 30, 2019: (in thousands) Remainder of 2019 $ 220,242 2020 500,908 2021 452,679 2022 382,294 2023 314,211 2024 259,139 Thereafter 977,267 Total $ 3,106,740 Other In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities ("ASU 2017-12"). ASU 2017-12 is designed to better align a company’s financial reporting for hedging activities with the economic objectives of those activities. The Company adopted ASU 2017-12 on January 1, 2019 and it did not have a material impact on the Company's consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software: Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract ("ASU 2018-15"). ASU 2018-15 amends the definition of a hosting arrangement and requires a customer in a hosting arrangement that is a service contract to capitalize certain implementation costs as if the arrangement was an internal-use software project. ASU 2018-15 is effective for the Company beginning January 1, 2020. The Company does not anticipate the impact of ASU 2018-15 will have a material impact on the consolidated financial statements.
Segment Reporting	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.
Discontinued Operations	The Company determined that the strategic shift would have a major effect on its operations and financial results. As such, properties sold or those that meet the criteria to be classified as held for sale within the corporate strategy were classified within discontinued operations. Consistent with the held for sale criteria these properties are expected to be sold within one year . As a result of the classification within discontinued operations, the in-service assets and liabilities of this portfolio are required to be presented as held for sale for all prior periods presented in our Consolidated Balance Sheets. Operating results pertaining to these properties were reclassified to discontinued operations for all prior periods presented in our Consolidated Statements of Comprehensive Income.
Fair Value of Financial Instruments	ASC 820, Fair Value Measurements and Disclosures , provides guidance on the fair value measurement of a financial asset or liability. Inputs used to develop fair value are classified in one of three categories: Level 1 inputs (quoted prices (unadjusted) in active markets for identical assets or liabilities), Level 2 inputs (inputs other than quoted prices that are observable for the asset or liability, either directly or indirectly) and Level 3 inputs (unobservable inputs for the asset or liability). 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 December 31, 2018 and September 30, 2019 . The use of different market assumptions and/or estimation methodologies may have a material effect on the estimated fair value amounts. The carrying value of cash and cash equivalents, restricted cash, accounts receivable, accounts payable, accrued interest, dividend and distributions payable and other liabilities are reasonable estimates of fair value because of the short-term nature of these instruments. The carrying value of the outstanding amounts under the Company's credit facilities is a reasonable estimate of fair value because interest rates float at a rate based on LIBOR. The Company determines the fair value of its interest rate swaps by using the standard methodology of netting discounted future fixed cash payments with the discounted expected variable cash receipts. These variable cash receipts of interest rate swaps are based on expectations of future LIBOR interest rates (forward curves) estimated by observing market LIBOR interest rate curves. This is a Level 2 fair value calculation. Also, credit valuation adjustments are factored into the fair value calculations to account for potential nonperformance risk. These credit valuation adjustments were concluded to not be significant inputs for the fair value calculations for the periods presented. See Note 14 - Derivative Instruments. The Company used a discounted cash flow model to determine the estimated fair value of its debt as of December 31, 2018 and September 30, 2019 . 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.

Segment Information Segment Inf

Segment Information Segment Information (Policies)	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Segment Reporting	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.

Impairment and Disposal of Lo_2

Impairment and Disposal of Long-Lived Assets Discontinued Operations (Policies)	9 Months Ended
	Sep. 30, 2019
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	The Company determined that the strategic shift would have a major effect on its operations and financial results. As such, properties sold or those that meet the criteria to be classified as held for sale within the corporate strategy were classified within discontinued operations. Consistent with the held for sale criteria these properties are expected to be sold within one year . As a result of the classification within discontinued operations, the in-service assets and liabilities of this portfolio are required to be presented as held for sale for all prior periods presented in our Consolidated Balance Sheets. Operating results pertaining to these properties were reclassified to discontinued operations for all prior periods presented in our Consolidated Statements of Comprehensive Income.

Disclosure of Fair Value of F_2

Disclosure of Fair Value of Financial Instruments Fair Value of Financial Instruments (Policies)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	ASC 820, Fair Value Measurements and Disclosures , provides guidance on the fair value measurement of a financial asset or liability. Inputs used to develop fair value are classified in one of three categories: Level 1 inputs (quoted prices (unadjusted) in active markets for identical assets or liabilities), Level 2 inputs (inputs other than quoted prices that are observable for the asset or liability, either directly or indirectly) and Level 3 inputs (unobservable inputs for the asset or liability). 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 December 31, 2018 and September 30, 2019 . The use of different market assumptions and/or estimation methodologies may have a material effect on the estimated fair value amounts. The carrying value of cash and cash equivalents, restricted cash, accounts receivable, accounts payable, accrued interest, dividend and distributions payable and other liabilities are reasonable estimates of fair value because of the short-term nature of these instruments. The carrying value of the outstanding amounts under the Company's credit facilities is a reasonable estimate of fair value because interest rates float at a rate based on LIBOR. The Company determines the fair value of its interest rate swaps by using the standard methodology of netting discounted future fixed cash payments with the discounted expected variable cash receipts. These variable cash receipts of interest rate swaps are based on expectations of future LIBOR interest rates (forward curves) estimated by observing market LIBOR interest rate curves. This is a Level 2 fair value calculation. Also, credit valuation adjustments are factored into the fair value calculations to account for potential nonperformance risk. These credit valuation adjustments were concluded to not be significant inputs for the fair value calculations for the periods presented. See Note 14 - Derivative Instruments. The Company used a discounted cash flow model to determine the estimated fair value of its debt as of December 31, 2018 and September 30, 2019 . 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.

Derivative Instruments Derivati

Derivative Instruments Derivative Instruments (Policies)	9 Months Ended
	Sep. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives, Policy [Policy Text Block]	The Company borrows funds at a combination of fixed and variable rates. Borrowings under the Company's revolving credit facility and certain bank mortgage loans bear interest at variable rates. Other long-term debt typically bears interest at fixed rates. The Company's interest rate risk management objectives are to limit generally the impact of interest rate changes on earnings and cash flows and to lower the Company's overall borrowing costs. To achieve these objectives, from time to time, the Company enters 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. The Company generally does not hold or issue these derivative contracts for trading or speculative purposes. 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 changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive loss and noncontrolling interest (for the Trust) and general partner's equity and limited partners ’ equity - common units (for the Operating Partnership) and is subsequently reclassified into interest expense in the period that the hedged forecasted transaction affects earnings. The Company determines the fair value of its interest rate swaps by netting discounted future fixed cash payments with the discounted expected variable cash receipts. These variable cash receipts of interest rate swaps are based on expectations of future LIBOR interest rates (forward curves) estimated by observing market LIBOR interest rate curves. This is a Level 2 fair value calculation. Also, credit valuation adjustments are factored into the fair value calculations to account for potential nonperformance risk. These credit valuation adjustments were concluded to be not significant inputs for the fair value calculations for the periods presented.

Organization and Basis of Pre_3

Organization and Basis of Presentation (Tables)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of future minimum rent payments	. The following schedule indicates the approximate future minimum lease payments for the ground and office leases as of September 30, 2019: Year Amount (in thousands) 2019 (remainder of year) $ 373 2020 1,370 2021 1,234 2022 1,136 2023 1,035 Thereafter 40,684 Total minimum payments $ 45,832 Imputed interest (26,941 ) Amortization (512 ) Lease liabilities $ 18,379 Deferred rent (715 ) Right of use asset $ 17,664
Future minimum rental payments	Since the Company has applied the provisions on a modified retrospective basis, the following represents approximate future minimum lease payments by year as of December 31, 2018, as applicable under ASC 840, Leases, prior to the adoption of the New Lease Standard. Year Amount (in thousands) 2019 $ 1,512 2020 1,356 2021 1,205 2022 1,082 2023 981 Thereafter 40,799 $ 46,935
Schedule of lease income	The following details the rental income and variable lease income for the three and nine months ended September 30, 2019 (in thousands): Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Rental income - operating leases - continuing operations $ 127,125 $ 371,744 Rental income - operating leases - discontinued operations 6,233 25,481 Variable lease income - operating leases - continuing operations 35,787 107,900 Variable lease income - operating leases - discontinued operations 2,265 8,112
Schedule of lease payments receivable	The following amounts reflect the estimated contractual rents due to the Company for the remainder of terms of the Company's operating leases as of September 30, 2019: (in thousands) Remainder of 2019 $ 220,242 2020 500,908 2021 452,679 2022 382,294 2023 314,211 2024 259,139 Thereafter 977,267 Total $ 3,106,740

Income per Common Share of th_2

Income per Common Share of the Trust (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Schedule of earnings per share	The following table sets forth the computation of basic and diluted income per common share of the Trust (in thousands except per share amounts): Three Months Ended Three Months Ended September 30, 2019 September 30, 2018 Income (Numerator) Weighted Average Shares (Denominator) Per Share Income (Numerator) Weighted Average Shares (Denominator) Per Share Income from continuing operations net of noncontrolling interest - basic $ 59,091 150,140 $ 0.39 $ 43,713 147,324 $ 0.30 Dilutive shares for long-term compensation plans — 839 — 947 Income from continuing operations net of noncontrolling interest - diluted $ 59,091 150,979 $ 0.39 $ 43,713 148,271 $ 0.29 Discontinued operations net of noncontrolling interests - basic $ 41,273 150,140 $ 0.28 $ 106,430 147,324 $ 0.72 Dilutive shares for long-term compensation plans — 839 — 947 Discontinued operations net of noncontrolling interests - diluted $ 41,273 150,979 $ 0.27 $ 106,430 148,271 $ 0.72 Net income available to common shareholders - basic $ 100,364 150,140 $ 0.67 $ 150,143 147,324 $ 1.02 Dilutive shares for long-term compensation plans — 839 — 947 Net income available to common shareholders - diluted $ 100,364 150,979 $ 0.66 $ 150,143 148,271 $ 1.01 Nine Months Ended Nine Months Ended September 30, 2019 September 30, 2018 Income Weighted Per Share Income Weighted Per Share Income from continuing operations net of noncontrolling interest - basic $ 151,150 148,532 $ 1.02 $ 91,051 147,241 $ 0.62 Dilutive shares for long-term compensation plans — 851 — 919 Income from continuing operations net of noncontrolling interest - diluted $ 151,150 149,383 $ 1.01 $ 91,051 148,160 $ 0.61 Discontinued operations net of noncontrolling interests - basic $ 103,315 148,532 $ 0.69 $ 218,887 147,241 $ 1.48 Dilutive shares for long-term compensation plans — 851 — 919 Discontinued operations net of noncontrolling interests - diluted $ 103,315 149,383 $ 0.69 $ 218,887 148,160 $ 1.48 Net income available to common shareholders - basic $ 254,465 148,532 $ 1.71 $ 309,938 147,241 $ 2.10 Dilutive shares for long-term compensation plans — 851 — 919 Net income available to common shareholders - diluted $ 254,465 149,383 $ 1.70 $ 309,938 148,160 $ 2.09

Income per Common Unit of the_2

Income per Common Unit of the Operating Partnership (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Unit, Basic and Diluted [Line Items]
Schedule of earnings per share	The following table sets forth the computation of basic and diluted income per common share of the Trust (in thousands except per share amounts): Three Months Ended Three Months Ended September 30, 2019 September 30, 2018 Income (Numerator) Weighted Average Shares (Denominator) Per Share Income (Numerator) Weighted Average Shares (Denominator) Per Share Income from continuing operations net of noncontrolling interest - basic $ 59,091 150,140 $ 0.39 $ 43,713 147,324 $ 0.30 Dilutive shares for long-term compensation plans — 839 — 947 Income from continuing operations net of noncontrolling interest - diluted $ 59,091 150,979 $ 0.39 $ 43,713 148,271 $ 0.29 Discontinued operations net of noncontrolling interests - basic $ 41,273 150,140 $ 0.28 $ 106,430 147,324 $ 0.72 Dilutive shares for long-term compensation plans — 839 — 947 Discontinued operations net of noncontrolling interests - diluted $ 41,273 150,979 $ 0.27 $ 106,430 148,271 $ 0.72 Net income available to common shareholders - basic $ 100,364 150,140 $ 0.67 $ 150,143 147,324 $ 1.02 Dilutive shares for long-term compensation plans — 839 — 947 Net income available to common shareholders - diluted $ 100,364 150,979 $ 0.66 $ 150,143 148,271 $ 1.01 Nine Months Ended Nine Months Ended September 30, 2019 September 30, 2018 Income Weighted Per Share Income Weighted Per Share Income from continuing operations net of noncontrolling interest - basic $ 151,150 148,532 $ 1.02 $ 91,051 147,241 $ 0.62 Dilutive shares for long-term compensation plans — 851 — 919 Income from continuing operations net of noncontrolling interest - diluted $ 151,150 149,383 $ 1.01 $ 91,051 148,160 $ 0.61 Discontinued operations net of noncontrolling interests - basic $ 103,315 148,532 $ 0.69 $ 218,887 147,241 $ 1.48 Dilutive shares for long-term compensation plans — 851 — 919 Discontinued operations net of noncontrolling interests - diluted $ 103,315 149,383 $ 0.69 $ 218,887 148,160 $ 1.48 Net income available to common shareholders - basic $ 254,465 148,532 $ 1.71 $ 309,938 147,241 $ 2.10 Dilutive shares for long-term compensation plans — 851 — 919 Net income available to common shareholders - diluted $ 254,465 149,383 $ 1.70 $ 309,938 148,160 $ 2.09
Liberty Property Limited Partnership
Earnings Per Unit, Basic and Diluted [Line Items]
Schedule of earnings per share	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): Three Months Ended Three Months Ended September 30, 2019 September 30, 2018 Income (Numerator) Weighted Average Units (Denominator) Per Unit Income (Numerator) Weighted Average Units (Denominator) Per Unit Income from continuing operations - net of noncontrolling interest - consolidated joint ventures $ 60,484 $ 44,865 Less: Preferred unit distributions (83 ) (118 ) Income from continuing operations available to common unitholders - basic $ 60,401 153,646 $ 0.39 $ 44,747 150,844 $ 0.30 Dilutive units for long-term compensation plans — 839 — 947 Income from continuing operations available to common unitholders - diluted $ 60,401 154,485 $ 0.39 $ 44,747 151,791 $ 0.29 Income from discontinued operations net of noncontrolling interest consolidated joint venture - basic $ 42,189 153,646 $ 0.28 $ 108,974 150,844 $ 0.72 Dilutive units for long-term compensation plans — 839 — 947 Income from discontinued operations net of noncontrolling interest consolidated joint venture - basic $ 42,189 154,485 $ 0.27 $ 108,974 151,791 $ 0.72 Income available to common unitholders - basic $ 102,590 153,646 $ 0.67 $ 153,721 150,844 $ 1.02 Dilutive units for long-term compensation plans — 839 — 947 Income available to common unitholders - diluted $ 102,590 154,485 $ 0.66 $ 153,721 151,791 $ 1.01 Nine Months Ended Nine Months Ended September 30, 2019 September 30, 2018 Income (Numerator) Weighted Average Units (Denominator) Per Unit Income (Numerator) Weighted Average Units (Denominator) Per Unit Net income - net of noncontrolling interest - consolidated joint ventures $ 154,872 $ 93,557 Less: Preferred unit distributions (251 ) (354 ) Income from continuing operations available to common unitholders - basic 154,621 152,045 $ 1.02 93,203 150,761 $ 0.62 Dilutive units for long-term compensation plans — 851 — 919 Income from continuing operations available to common unitholders - diluted $ 154,621 152,896 $ 1.01 $ 93,203 151,680 $ 0.61 Income from discontinued operations net of noncontrolling interest consolidated joint venture - basic $ 105,719 152,045 $ 0.69 $ 224,119 150,761 $ 1.48 Dilutive units for long-term compensation plans — 851 — 919 Income from discontinued operations net of noncontrolling interest consolidated joint venture - basic $ 105,719 152,896 $ 0.69 $ 224,119 151,680 $ 1.48 Net income available to common unitholders - basic $ 260,340 152,045 $ 1.71 $ 317,322 150,761 $ 2.10 Dilutive units for long-term compensation plans — 851 — 919 Net income available to common unitholders - diluted $ 260,340 152,896 $ 1.70 $ 317,322 151,680 $ 2.09

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of accumulated other comprehensive income	The following table sets forth the components of Accumulated Other Comprehensive Loss (in thousands): As of and for the nine months ended September 30, 2019 2018 Foreign Currency Translation: Beginning balance $ (52,862 ) $ (38,701 ) Translation adjustment (7,574 ) (9,221 ) Ending balance (60,436 ) (47,922 ) Derivative Instruments: Beginning balance (3,550 ) 150 Unrealized gain (1,820 ) 620 Reclassification adjustment (1) (67 ) (127 ) Ending balance (5,437 ) 643 Total accumulated other comprehensive loss (65,873 ) (47,279 ) Less: portion included in noncontrolling interest – operating partnership 1,377 957 Total accumulated other comprehensive loss included in shareholders' equity/owners' equity $ (64,496 ) $ (46,322 ) (1) Amounts reclassified out of Accumulated Other Comprehensive Loss/General & Limited Partner's Equity into contractual interest expense.

Real Estate (Tables)

Real Estate (Tables)	9 Months Ended
	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Schedule of operating properties and land parcels	Information on the Operating Properties and land parcels the Company acquired during the three months and nine months ended September 30, 2019 is as follows: Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 Number of Buildings Acres of Developable Land Leaseable Square Feet Purchase Price (in thousands) Number of Buildings Acres of Developable Land Leaseable Square Feet Purchase Price (in thousands) Chicago/Minneapolis — 23.5 — $ 13,200 — 23.5 — $ 13,200 Dallas — — — — 2 — 509,733 44,400 Southern California 1 — 203,280 55,500 2 — 492,963 86,785 United Kingdom — — — — — 25.0 — 2,658 Other: Atlanta — — — — — 154.7 — 5,000 New Jersey — — — — 3 — 488,254 78,275 1 23.5 203,280 $ 68,700 7 203.2 1,490,950 $ 230,318 In the nine months ended September 30, 2019, the Company purchased the noncontrolling interest of three consolidated joint ventures in the following reportable segments: four buildings in Philadelphia, one building in New Jersey, one building in Dallas and one building in Southern California as well as 21.7 acres of land in Arizona, for $18.5 million . Information on the Operating Properties and land parcels the Company sold during the three and nine months ended September 30, 2019 is as follows: Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 Number of Buildings Acres of Developable Land Leaseable Square Feet Gross Proceeds (in thousands) Number of Buildings Acres of Developable Land Leaseable Square Feet Gross Proceeds (in thousands) Carolinas/Richmond 1 — 136,000 $ 14,100 1 — 136,000 $ 14,100 Chicago/Minneapolis — — — — — 11.3 — 2,865 Florida — — — — 3 — 150,751 23,400 Houston — 7.6 — 1,700 — 11.6 — 3,205 Philadelphia 2 — 156,411 60,650 3 — 309,653 159,900 Other: Arizona — — — — — 8.8 — 11,500 New Jersey (1) — 67.6 — 4,070 — 68.4 — 8,070 DC Metro 1 — 290,762 92,500 2 — 437,234 154,250 Southeastern PA 2 — 180,151 30,000 5 18.0 254,331 40,200 6 75.2 763,324 $ 203,020 14 118.1 1,287,969 $ 417,490 (1) Includes land that the Company sold for $4.1 million to an unconsolidated joint venture in which the Company holds a 25% interest. In connection with the sale of a building in the Philadelphia reportable segment in June 2019 the Company repaid a $35.9 million 4.84% mortgage loan due 2033 encumbering the property and, consequently, recognized a loss of $7.6 million on early extinguishment of debt, which is reported in discontinued operations. In addition to the sale of land parcels described above, the Company also received gross proceeds of $5.5 million from the sale of non-depreciable assets in Tempe, Arizona included in Company’s Other reportable segment in the third quarter of 2019, as well as $4.0 million from the sale of non-depreciable assets in Camden, New Jersey included in the Company’s Philadelphia reportable segment during the nine months ended September 30, 2019. Including the above-described sales of land and other non-depreciable assets, the Company recognized gains on sales of non-depreciable assets of $7.0 million and $12.9 million during the three and nine months ended September 30, 2019, respectively. In addition to the transactions described above, during the three and nine months ended September 30, 2019, a subsidiary of the Company entered into an agreement with an entity affiliated with an employee of the Company, pursuant to which the Company waived its rights to purchase and develop a particular land parcel in Company’s Philadelphia reportable segment in consideration for reimbursement of a portion of the infrastructure costs totaling $3.2 million

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Schedule of operating information by reportable segment	The operating information by reportable segment is as follows (in thousands): Three Months Ended Nine Months Ended September 30, 2019 September 30, 2018 September 30, 2019 September 30, 2018 Revenue Carolinas/Richmond $ 20,377 $ 19,417 $ 61,129 $ 58,723 Chicago/Minneapolis 17,479 17,274 52,299 50,414 Cincinnati/Columbus/Indianapolis 4,792 4,245 13,822 13,613 Dallas 5,953 5,537 17,252 14,300 Florida 15,871 15,847 48,218 47,117 Houston 19,103 16,561 51,831 48,514 Lehigh/Central PA 38,878 39,188 118,588 115,799 Philadelphia 9,779 10,598 32,043 33,659 Southern California 10,510 7,914 30,660 22,226 United Kingdom 5,900 3,523 17,857 11,579 Other 22,768 32,119 69,717 97,853 Segment-level revenue 171,410 172,223 513,416 513,797 Reconciliation to total revenue Development service fee income 257 12,956 2,099 59,132 Discontinued operations (8,498 ) (23,911 ) (33,593 ) (73,613 ) Other — 18 (179 ) (372 ) Total revenue $ 163,169 $ 161,286 $ 481,743 $ 498,944 Net operating income Carolinas/Richmond $ 15,638 $ 14,620 $ 47,020 $ 43,795 Chicago/Minneapolis 10,902 10,564 33,294 31,271 Cincinnati/Columbus/Indianapolis 3,262 2,749 9,186 9,099 Dallas 4,035 3,666 11,848 9,274 Florida 11,628 11,461 35,097 33,717 Houston 12,377 9,676 32,159 28,714 Lehigh/Central PA 29,902 29,406 89,639 86,085 Philadelphia 7,876 7,947 25,583 28,211 Southern California 8,200 6,496 23,524 17,675 United Kingdom 5,421 3,234 16,131 10,662 Other 15,507 23,213 47,727 69,620 Net operating income 124,748 123,032 371,208 368,123 Reconciliation to income from continuing operations Interest expense (1) (26,220 ) (24,670 ) (78,297 ) (71,331 ) Development service fee income 257 12,956 2,099 59,132 Development service fee expense (168 ) (12,924 ) (1,848 ) (120,799 ) Depreciation/amortization expense (1) (2) (32,279 ) (32,243 ) (97,642 ) (97,576 ) Impairment charges - real estate assets — — (99 ) (26,000 ) Gain on property dispositions 15,168 2,002 21,125 54,705 Equity in earnings of unconsolidated joint ventures 1,776 6,766 10,966 20,958 General and administrative expense (1) (10,193 ) (9,814 ) (35,559 ) (32,758 ) Leasing cost (3,082 ) (2,610 ) (9,608 ) (8,189 ) Other operating expenses (3,166 ) (3,169 ) (8,690 ) (7,467 ) Discontinued operations excluding losses on impairment and debt extinguishment and gain on property dispositions (4,951 ) (14,320 ) (18,553 ) (39,842 ) Income taxes (1) (2) (811 ) (329 ) (1,635 ) (1,539 ) Other (592 ) 196 1,389 (3,262 ) Income from continuing operations $ 60,487 $ 44,873 $ 154,856 $ 94,155 (1) Includes activity in discontinued operations. (2) Excludes costs that are included in determining net operating income.
Schedule of total assets by reportable segments	The Company's total assets by reportable segment as of September 30, 2019 and December 31, 2018 is as follows (in thousands): September 30, 2019 December 31, 2018 Carolinas/Richmond $ 516,811 $ 525,041 Chicago/Minnesota 597,557 591,792 Cincinnati/Columbus/Indianapolis 134,111 131,400 Dallas 306,463 261,538 Florida 550,623 547,232 Houston 608,761 568,756 Lehigh/Central PA 1,225,016 1,210,220 Philadelphia 540,972 624,373 Southern California 766,578 660,688 United Kingdom 392,091 463,162 Other 1,062,447 1,153,518 Segment-level total assets 6,701,430 6,737,720 Corporate Other 637,302 196,674 Total assets $ 7,338,732 $ 6,934,394

Impairment and Disposal of Lo_3

Impairment and Disposal of Long-Lived Assets Impairment and Disposal of Long-Lived Assets (Tables)	9 Months Ended
	Sep. 30, 2019
Discontinued Operations and Disposal Groups [Abstract]
Schedule of disposal groups	The following table illustrates aggregate balance sheet information for all held for sale properties (in thousands): September 30, 2019 December 31, 2018 Included in Continuing Operations Included in Discontinued Operations Total Included in Continuing Operations Included in Discontinued Operations Total Land and land improvements $ 613 $ 19,210 $ 19,823 $ 1,301 $ 113,080 $ 114,381 Buildings and improvements 8,541 174,595 183,136 5,638 384,737 390,375 Development in progress — 10,108 10,108 — 9,597 9,597 Land held for development 19,420 — 19,420 26,253 — 26,253 Accumulated depreciation (3,745 ) (21,592 ) (25,337 ) (1,546 ) (70,242 ) (71,788 ) Deferred financing and leasing costs, net 717 7,910 8,627 58 13,697 13,755 Other assets 756 9,971 10,727 164 19,470 19,634 Total assets held for sale $ 26,302 $ 200,202 $ 226,504 $ 31,868 $ 470,339 $ 502,207 Total liabilities held for sale $ 419 $ 15,520 $ 15,939 $ 141 $ 20,990 $ 21,131 A summary of the results of operations for the properties classified as discontinued operations is as follows (in thousands): Three Months Ended Nine Months Ended September 30, 2019 September 30, 2018 September 30, 2019 September 30, 2018 Revenues $ 8,498 $ 23,911 $ 33,593 $ 73,613 Operating expenses (3,117 ) (5,329 ) (10,903 ) (17,276 ) Depreciation and amortization — (2,666 ) (2,129 ) (11,138 ) Impairment charges - real estate assets (7,190 ) — (21,482 ) — Interest and other income (expense) 4 (31 ) (57 ) (132 ) Income taxes (5 ) (28 ) (298 ) (83 ) Loss on debt extinguishment — — (7,618 ) — Interest expense (429 ) (1,537 ) (1,653 ) (5,142 ) Gain on property dispositions 44,428 94,878 116,452 184,689 Income from discontinued operations 42,189 109,198 105,905 224,531 Noncontrolling interest - operating partnership (916 ) (2,544 ) (2,404 ) (5,232 ) Noncontrolling interest - consolidated joint venture — (224 ) (186 ) (412 ) Income from discontinued operations available to common shareholders $ 41,273 $ 106,430 $ 103,315 $ 218,887 The following table illustrates the number of sold or held for sale properties included in, or excluded from, discontinued operations: Held for sale as of September 30, 2019 Sold during the nine months ended September 30, 2019 Sold during the year ended December 31, 2018 Total Properties included in discontinued operations 9 13 37 59 Properties included in continuing operations 1 1 2 4 Properties sold or classified as held for sale 10 14 39 63

Noncontrolling Interest - Ope_2

Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units (Tables)	9 Months Ended
	Sep. 30, 2019
Temporary Equity [Line Items]
Schedule of preferred units	As of September 30, 2019 , the Company had outstanding the following cumulative preferred units of the Operating Partnership: ISSUE AMOUNT UNITS LIQUIDATION PREFERENCE DIVIDEND RATE (in 000’s) Series I-2 $ 5,337 213 $ 25 6.25 %

Disclosure of Fair Value of F_3

Disclosure of Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2019
Debt Instrument, Fair Value Disclosure [Abstract]
Schedule of fair value	The following summarizes the fair value of the Company's mortgage loans and unsecured notes as of December 31, 2018 and September 30, 2019 (in thousands): Mortgage Loans Unsecured Notes Carrying Value Fair Value Carrying Value Fair Value As of December 31, 2018 $ 395,202 $ 397,167 $ 2,285,698 $ 2,295,699 As of September 30, 2019 $ 297,326 $ 304,689 $ 2,633,941 $ 2,821,931

Derivative Instruments (Tables)

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of gains or losses recognized related to derivatives	The following table presents the location in the financial statements of the gains or losses recognized related to the Company’s cash flow hedges for the three and nine months ended September 30, 2019 and 2018 (in thousands): Three Months Ended Nine Months Ended September 30, 2019 September 30, 2018 September 30, 2019 September 30, 2018 Amount of gain related to the effective portion recognized in other comprehensive (loss) income $ 13 $ 69 $ 424 $ 619 Total Amount of Interest Expense Presented in the Consolidated Statements of Comprehensive Income 25,791 23,133 76,644 66,189
Schedule of derivative instruments, classification on the accompanying balance sheets	The following table presents the fair value of the Company’s derivative financial instruments as well as their classification on the accompanying consolidated balance sheets as of September 30, 2019 and December 31, 2018 (amounts in thousands): Derivatives Fair Value at: Balance Sheet Location September 30, 2019 December 31, 2018 Derivatives designated as hedging instruments: Interest Rate Swaps Other Liabilities $ 345 $ 677 Interest Rate Treasury Locks Other Liabilities — 3,972 Total $ 345 $ 4,649

Supplemental Disclosure to St_2

Supplemental Disclosure to Statements of Cash Flows (Tables)	9 Months Ended
	Sep. 30, 2019
Supplemental Cash Flow Information [Abstract]
Schedule of supplemental disclosure to statement of cash flows	The following is a reconciliation of the Company's cash and cash equivalents and restricted cash at the beginning and end of the nine months ended September 30, 2019 and 2018 (amounts in thousands): 2019 2018 Cash and cash equivalents at beginning of period $ 84,923 $ 11,882 Restricted cash at beginning of period 10,899 13,803 Cash and cash equivalents and restricted cash at beginning of period $ 95,822 $ 25,685 Cash and cash equivalents at end of period $ 514,882 $ 17,770 Restricted cash at end of period 14,006 13,371 Cash and cash equivalents and restricted cash at end of period $ 528,888 $ 31,141 The following are supplemental disclosures to the consolidated statements of cash flows for the nine months ended September 30, 2019 and 2018 (amounts in thousands): 2019 2018 Write-off of fully depreciated/amortized property and deferred costs - properties included in continuing operations $ 2,218 $ 7,197 Write-off of fully depreciated/amortized property and deferred costs - properties included in discontinued operations $ — $ 11,789 Write-off of depreciated property and deferred costs due to sale/demolition - properties included in continuing operations $ 1,642 $ 20,273 Write-off of depreciated property and deferred costs due to sale and related debt repayment - properties included in discontinued operations $ 51,455 $ 99,072 Changes in accrued development capital expenditures - properties included in continuing operations $ (4,436 ) $ 12,361 Changes in accrued development capital expenditures - properties included in discontinued operations $ — $ (4,628 ) Unrealized (loss) gain on cash flow hedge $ (1,887 ) $ 493 Capitalized equity-based compensation $ 915 $ 727

Organization and Basis of Pre_4

Organization and Basis of Presentation - Organization (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Ownership interest in operating partnership - Limited Partnership	97.80%
Liberty Comcast 1701 JFK Boulevard, LP
Variable Interest Entity [Line Items]
Ownership percentage of equity method investment	20.00%
Liberty Comcast 1701 JFK Boulevard, LP | Variable Interest Entity, Not Primary Beneficiary | Other Investments
Variable Interest Entity [Line Items]
Equity investment in joint venture	$ 73.9	$ 75.1

Organization and Basis of Pre_5

Organization and Basis of Presentation - Basis of Presentation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from contracts	$ 257	$ 12,956	$ 2,099	$ 59,132
Revenue from remaining performance obligation	28,100		28,100
United Kingdom
Disaggregation of Revenue [Line Items]
Revenue from contracts	$ 4,500		$ 10,400

Organization and Basis of Pre_6

Organization and Basis of Presentation - Ground Leases (Details) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2019USD ($)properties	Sep. 30, 2019USD ($)properties	Dec. 31, 2018USD ($)
Lessee, Lease, Description [Line Items]
Number of properties subject to ground lease (in properties) | properties	5	5
Weighted average remaining lease term	47 years	47 years
Term of contract	11 years	11 years
Useful life increase interval		5 years
Weighted average discount rate	4.60%	4.60%
Operating Lease, Expense	$ 0.5	$ 1.5
Leasing expense			$ 1.5
Cash portion of lease expense	$ 0.5	$ 1.4
Minimum
Lessee, Lease, Description [Line Items]
Renewal term	25 years	25 years
Weighted average discount rate	4.10%	4.10%
Maximum
Lessee, Lease, Description [Line Items]
Term of contract	110 years	110 years
Renewal term	48 years	48 years
Weighted average discount rate	5.00%	5.00%
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Leasing expense	$ 0.1	$ 0.7

Organization and Basis of Pre_7

Organization and Basis of Presentation - Future Minimum Lease Payments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2019
Ground Leases Disclosures [Abstract]
2019 (remainder of year)		$ 373
2020		1,370
2021		1,234
2022		1,136
2023		1,035
Thereafter		40,684
Total minimum payments		45,832
Imputed interest		(26,941)
Amortization		(512)
Lease liabilities	$ 0	18,379
Deferred rent		(715)
Right of use asset	0	17,664
Leases, Operating [Abstract]
2019	1,512
2020	1,356
2021	1,205
2022	1,082
2023	981
Thereafter	40,799
Future minimum payments due	46,935
Leasing expense	$ 1,500
Operating Leases Receivable
Remainder of 2019		220,242
2020		500,908
2021		452,679
2022		382,294
2023		314,211
2024		259,139
Thereafter		977,267
Total		$ 3,106,740

Organization and Basis of Pre_8

Organization and Basis of Presentation Rental Income Lessor (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Continuing Operations
Lessor, Lease, Description [Line Items]
Rental income - operating leases	$ 127,125	$ 371,744
Variable lease income - operating leases	35,787	107,900
Discontinued operations
Lessor, Lease, Description [Line Items]
Rental income - operating leases	6,233	25,481
Variable lease income - operating leases	$ 2,265	$ 8,112

Income per Common Share of th_3

Income per Common Share of the Trust (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share, Basic and Diluted [Line Items]
Document Period End Date			Sep. 30, 2019
Income (Numerator) [Abstract]
Income from continuing operations net of noncontrolling interest	$ 59,091	$ 43,713	$ 151,150	$ 91,051
Income from discontinued operations net of noncontrolling interest	41,273	106,430	103,315	218,887
Net income available to common shareholders	$ 100,364	$ 150,143	$ 254,465	$ 309,938
Weighted Average Shares (Denominator) [Abstract]
Income from continuing operations net of noncontrolling interest - basic, weighted average shares (in shares)	150,140	147,324	148,532	147,241
Dilutive shares for long-term compensation plans, weighted average shares (in shares)	839	947	851	919
Income from continuing operations net of noncontrolling interest - diluted, weighted average shares (in shares)	150,979	148,271	149,383	148,160
Common shares
Earnings Per Share, Basic [Abstract]
Income from continuing operations (in usd per share)	$ 0.39	$ 0.30	$ 1.02	$ 0.62
Income from discontinued operations (in usd per share)	0.28	0.72	0.69	1.48
Income per common share or unit - basic (in usd per share)	0.67	1.02	1.71	2.10
Earnings Per Share, Diluted [Abstract]
Income from continuing operations (in usd per share)	0.39	0.29	1.01	0.61
Income from discontinued operations (in usd per share)	0.27	0.72	0.69	1.48
Income per common share or unit - diluted (in usd per share)	$ 0.66	$ 1.01	$ 1.70	$ 2.09

Income per Common Share of th_4

Income per Common Share of the Trust Income per Common Share of the Trust - Anti-dilutive Options (Details) - shares	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Stock Option
Antidilutive Options Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive options excluded from computation of earnings per share	0	0	0	0
Common shares | 2017 Share Repurchase Program
Antidilutive Options Excluded from Computation of Earnings Per Share [Line Items]
Stock repurchased in period (in shares)	0		0		0

Income per Common Share of th_5

Income per Common Share of the Trust - Options Exercised (Details) - shares	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Stock Option | Common shares
Stock Option Exercises [Line Items]
Amount of options exercised in period	251,000	374,000	151,000

Income per Common Share of th_6

Income per Common Share of the Trust - Share Repurchase (Details) - 2017 Share Repurchase Program - Common shares - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Equity, Class of Treasury Stock [Line Items]
Share repurchase program, authorized amount	$ 250	$ 250
Stock repurchased in period (in shares)	0	0	0

Income per Common Share of th_7

Income per Common Share of the Trust Equity Offering (Details) - Common shares $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended
	Sep. 30, 2019USD ($)$ / sharesshares
Class of Shares [Line Items]
Shares, Issued | shares	9.2
Shares Issued, Price Per Share | $ / shares	$ 50.50
Proceeds from Issuance of Shares | $	$ 447.9

Income per Common Share of th_8

Income per Common Share of the Trust Subsequent Event (Details) - USD ($) $ in Thousands	Oct. 12, 2019	Sep. 30, 2019	Sep. 30, 2018
Subsequent Event [Line Items]
Loss on debt extinguishment		$ (7,618)	$ 0
Subsequent Event [Member]
Subsequent Event [Line Items]
Loss on debt extinguishment	$ (9,000)
Unsecured Notes | Subsequent Event [Member]
Subsequent Event [Line Items]
Repayments of unsecured notes	$ 350,000
Interest Rate	4.75%

Income per Common Unit of the_3

Income per Common Unit of the Operating Partnership - Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income (Numerator) [Abstract]
Income from continuing operations net of noncontrolling interest	$ 59,091	$ 43,713	$ 151,150	$ 91,051
Income from discontinued operations	41,273	106,430	103,315	218,887
Net income available to common shareholders	$ 100,364	$ 150,143	$ 254,465	$ 309,938
Weighted Average Units (Denominator) [Abstract]
Income from continuing operations net of noncontrolling interest - basic, weighted average shares (in shares)	150,140	147,324	148,532	147,241
Dilutive units for long-term compensation plans	839	947	851	919
Income from continuing operations net of noncontrolling interest - diluted, weighted average shares (in shares)	150,979	148,271	149,383	148,160
Liberty Property Limited Partnership
Income (Numerator) [Abstract]
Income from continuing operations net of noncontrolling interest	$ 60,484	$ 44,865	$ 154,872	$ 93,557
Preferred unit distributions	(83)	(118)	(251)	(354)
Income from continuing operations available to common unitholders	60,401	44,747	154,621	93,203
Income from discontinued operations	42,189	108,974	105,719	224,119
Net income available to common shareholders	$ 102,590	$ 153,721	$ 260,340	$ 317,322
Weighted Average Units (Denominator) [Abstract]
Income from continuing operations net of noncontrolling interest - basic, weighted average shares (in shares)	153,646	150,844	152,045	150,761
Dilutive units for long-term compensation plans	839	947	851	919
Income from continuing operations net of noncontrolling interest - diluted, weighted average shares (in shares)	154,485	151,791	152,896	151,680
Liberty Property Limited Partnership | Common Units
Earnings Per Unit, Basic [Abstract]
Income from continuing operations (in usd per share)	$ 0.39	$ 0.30	$ 1.02	$ 0.62
Income from discontinued operations (in usd per share)	0.28	0.72	0.69	1.48
Income per common share or unit - basic (in usd per share)	0.67	1.02	1.71	2.10
Earnings Per Unit, Diluted [Abstract]
Income from continuing operations (in usd per share)	0.39	0.29	1.01	0.61
Income from discontinued operations (in usd per share)	0.27	0.72	0.69	1.48
Income per common share or unit - diluted (in usd per share)	$ 0.66	$ 1.01	$ 1.70	$ 2.09

Income per Common Unit of the_4

Income per Common Unit of the Operating Partnership - Anti-dilutive Options (Details) - shares	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Stock Option
Antidilutive Options Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive options excluded from computation of earnings per share	0	0	0	0
Liberty Property Limited Partnership | Stock Option
Antidilutive Options Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive options excluded from computation of earnings per share	0	0	0	0
Common Units | 2017 Share Repurchase Program | Liberty Property Limited Partnership
Antidilutive Options Excluded from Computation of Earnings Per Share [Line Items]
Stock repurchased in period (in shares)	0		0		0

Income per Common Unit of the_5

Income per Common Unit of the Operations Partnership - Options Exercised (Details) - shares	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Liberty Property Limited Partnership | Stock Option | Common Units
Stock Option Exercises [Line Items]
Amount of options exercised in period	251,000	374,000	151,000

Income per Common Unit of the_6

Income per Common Unit of the Operating Partnership Unit Repurchase (Details) - Liberty Property Limited Partnership - 2017 Share Repurchase Program - Common Units - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Equity, Class of Treasury Stock [Line Items]
Share repurchase program, authorized amount	$ 250	$ 250
Stock repurchased in period (in shares)	0	0	0

Income per Common Unit of the_7

Income per Common Unit of the Operating Partnership Equity Offering (Details) - Liberty Property Limited Partnership - Common Units $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended
	Sep. 30, 2019USD ($)$ / sharesshares
Class of Shares [Line Items]
Units, Issued | shares	9.2
Units Issued, Price Per Unit | $ / shares	$ 50.50
Proceeds from Issuance of Units | $	$ 447.9

Income per Common Unit of the_8

Income per Common Unit of the Operating Partnership Subsequent Event (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	Oct. 12, 2019	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018
Subsequent Event [Line Items]
Loss on debt extinguishment			$ (7,618)	$ 0
Subsequent Event [Member]
Subsequent Event [Line Items]
Loss on debt extinguishment	$ (9,000)
Unsecured Notes | Subsequent Event [Member]
Subsequent Event [Line Items]
Repayments of unsecured notes	$ 350,000
Interest Rate	4.75%
Liberty Property Limited Partnership
Subsequent Event [Line Items]
Loss on debt extinguishment			$ (7,618)	$ 0
Liberty Property Limited Partnership | Subsequent Event [Member]
Subsequent Event [Line Items]
Loss on debt extinguishment	$ (9,000)
Liberty Property Limited Partnership | Unsecured Notes | Subsequent Event [Member]
Subsequent Event [Line Items]
Repayments of unsecured notes	$ 350,000
Interest Rate	4.75%
Common Units | Liberty Property Limited Partnership
Subsequent Event [Line Items]
Shares, Issued		9.2	9.2
Shares Issued, Price Per Share		$ 50.50	$ 50.50
Proceeds from Issuance of Units		$ 447,900

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 3,396,772	$ 3,148,366
Ending balance	3,905,443	3,289,584
Total accumulated other comprehensive loss	3,905,443	3,148,366	$ 3,905,443	$ 3,417,364	$ 3,396,772	$ 3,289,584	$ 3,197,225
Total accumulated other comprehensive loss included in shareholders' equity/owners' equity			3,842,855		3,329,861
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(52,862)	(38,701)
Unrealized income (loss)	(7,574)	(9,221)
Ending balance	(60,436)	(47,922)
Total accumulated other comprehensive loss	(52,862)	(38,701)	(60,436)		(52,862)	(47,922)
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(3,550)	150
Unrealized income (loss)	(1,820)	620
Reclassification adjustment	(67)	(127)
Ending balance	(5,437)	643
Total accumulated other comprehensive loss	(3,550)	150	(5,437)		(3,550)	643
AOCI Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending balance	(65,873)	(47,279)
Total accumulated other comprehensive loss	(65,873)	(47,279)	(65,873)			(47,279)
AOCI Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending balance	1,377	957
Total accumulated other comprehensive loss	1,377	957	1,377			957
AOCI Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(55,243)	(37,797)
Ending balance	(64,496)	(46,322)
Total accumulated other comprehensive loss	$ (64,496)	$ (46,322)	(64,496)	$ (57,674)	$ (55,243)	(46,322)	$ (43,383)
Total accumulated other comprehensive loss included in shareholders' equity/owners' equity			$ (64,496)			$ (46,322)

Real Estate (Details)

Real Estate (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2019USD ($)	Sep. 30, 2019USD ($)aft²bldg	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)aft²bldg	Sep. 30, 2018USD ($)
Property, Plant and Equipment [Line Items]
Loss on debt extinguishment				$ (7,618)	$ 0
Net proceeds from disposition of properties/land				412,474	574,542
Repayments of Secured Debt				98,467	31,954
Acquisition of noncontrolling interest				18,513
Discontinued operations
Property, Plant and Equipment [Line Items]
Loss on debt extinguishment		$ 0	$ 0	$ (7,618)	$ 0
2019 acquisitions [Member] | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		7		7
Leaseable Square Feet (in sqft) | ft²		1,490,950		1,490,950
2019 acquisitions [Member] | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		203.2		203.2
2019 acquisitions [Member] | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Purchase Price (in thousands)				$ 230,318
2019 acquisitions [Member] | Dallas | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		2		2
Leaseable Square Feet (in sqft) | ft²		509,733		509,733
2019 acquisitions [Member] | Dallas | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Purchase Price (in thousands)				$ 44,400
2019 acquisitions [Member] | Chicago/Minneapolis | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		23.5		23.5
2019 acquisitions [Member] | Chicago/Minneapolis | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Purchase Price (in thousands)				$ 13,200
2019 acquisitions [Member] | Southern California | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		2		2
Leaseable Square Feet (in sqft) | ft²		492,963		492,963
2019 acquisitions [Member] | Southern California | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Purchase Price (in thousands)				$ 86,785
2019 acquisitions [Member] | United Kingdom | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		25		25
2019 acquisitions [Member] | United Kingdom | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Purchase Price (in thousands)				$ 2,658
2019 acquisitions [Member] | Atlanta | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		154.7		154.7
2019 acquisitions [Member] | Atlanta | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Purchase Price (in thousands)				$ 5,000
2019 acquisitions [Member] | New Jersey | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		3		3
Leaseable Square Feet (in sqft) | ft²		488,254		488,254
2019 acquisitions [Member] | New Jersey | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Purchase Price (in thousands)				$ 78,275
2019 acquisitions current quarter [Member] | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		1		1
Leaseable Square Feet (in sqft) | ft²		203,280		203,280
2019 acquisitions current quarter [Member] | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		23.5		23.5
2019 acquisitions current quarter [Member] | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Purchase Price (in thousands)		$ 68,700
2019 acquisitions current quarter [Member] | Chicago/Minneapolis | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		23.5		23.5
2019 acquisitions current quarter [Member] | Chicago/Minneapolis | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Purchase Price (in thousands)		$ 13,200
2019 acquisitions current quarter [Member] | Southern California | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		1		1
Leaseable Square Feet (in sqft) | ft²		203,280		203,280
2019 acquisitions current quarter [Member] | Southern California | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Purchase Price (in thousands)		$ 55,500
2019 acquisitions of noncontrolling interest
Property, Plant and Equipment [Line Items]
Number of Consolidated Joint Ventures		3		3
2019 acquisitions of noncontrolling interest | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Purchase Price (in thousands)				$ 18,500
2019 acquisitions of noncontrolling interest | Dallas | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		1		1
2019 acquisitions of noncontrolling interest | Philadelphia | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		4		4
2019 acquisitions of noncontrolling interest | Southern California | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		1		1
2019 acquisitions of noncontrolling interest | Arizona | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		21.7		21.7
2019 acquisitions of noncontrolling interest | New Jersey | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		1		1
2019 sales current quarter | Disposal Group, Not Discontinued Operations | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		6		6
Leaseable Square Feet (in sqft) | ft²		763,324		763,324
2019 sales current quarter | Disposal Group, Not Discontinued Operations | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		75.2		75.2
2019 sales current quarter | Disposal Group, Not Discontinued Operations | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)		$ 203,020
2019 sales current quarter | Disposal Group, Not Discontinued Operations | Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Gain on sale of nondepreciable assets		$ 7,000
2019 sales current quarter | Disposal Group, Not Discontinued Operations | Houston | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		7.6		7.6
2019 sales current quarter | Disposal Group, Not Discontinued Operations | Houston | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)		$ 1,700
2019 sales current quarter | Disposal Group, Not Discontinued Operations | Philadelphia | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		2		2
Leaseable Square Feet (in sqft) | ft²		156,411		156,411
2019 sales current quarter | Disposal Group, Not Discontinued Operations | Philadelphia | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)		$ 60,650
2019 sales current quarter | Disposal Group, Not Discontinued Operations | Arizona | Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)		$ 5,500
2019 sales current quarter | Disposal Group, Not Discontinued Operations | Southeastern PA | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		2		2
Leaseable Square Feet (in sqft) | ft²		180,151		180,151
2019 sales current quarter | Disposal Group, Not Discontinued Operations | Southeastern PA | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)		$ 30,000
2019 sales current quarter | Disposal Group, Not Discontinued Operations | New Jersey | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		67.6		67.6
2019 sales current quarter | Disposal Group, Not Discontinued Operations | New Jersey | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)		$ 4,070
2019 sales current quarter | Disposal Group, Not Discontinued Operations | DC Metro | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		1		1
Leaseable Square Feet (in sqft) | ft²		290,762		290,762
2019 sales current quarter | Disposal Group, Not Discontinued Operations | DC Metro | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)		$ 92,500
2019 sales current quarter | Operating Segments | Disposal Group, Not Discontinued Operations | Carolinas/Richmond | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		1		1
Leaseable Square Feet (in sqft) | ft²		136,000		136,000
2019 sales current quarter | Operating Segments | Disposal Group, Not Discontinued Operations | Carolinas/Richmond | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)		$ 14,100
2019 sales | Philadelphia
Property, Plant and Equipment [Line Items]
Repayments of Secured Debt	$ (35,900)
2019 sales | Disposal Group, Not Discontinued Operations | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		14		14
Leaseable Square Feet (in sqft) | ft²		1,287,969		1,287,969
2019 sales | Disposal Group, Not Discontinued Operations | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		118.1		118.1
2019 sales | Disposal Group, Not Discontinued Operations | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)				$ 417,490
2019 sales | Disposal Group, Not Discontinued Operations | Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Gain on sale of nondepreciable assets				$ 12,900
2019 sales | Disposal Group, Not Discontinued Operations | Chicago/Minneapolis | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		11.3		11.3
2019 sales | Disposal Group, Not Discontinued Operations | Chicago/Minneapolis | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)				$ 2,865
2019 sales | Disposal Group, Not Discontinued Operations | Florida | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		3		3
Leaseable Square Feet (in sqft) | ft²		150,751		150,751
2019 sales | Disposal Group, Not Discontinued Operations | Florida | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)				$ 23,400
2019 sales | Disposal Group, Not Discontinued Operations | Houston | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		11.6		11.6
2019 sales | Disposal Group, Not Discontinued Operations | Houston | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)				$ 3,205
2019 sales | Disposal Group, Not Discontinued Operations | Philadelphia | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		3		3
Leaseable Square Feet (in sqft) | ft²		309,653		309,653
2019 sales | Disposal Group, Not Discontinued Operations | Philadelphia | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)				$ 159,900
2019 sales | Disposal Group, Not Discontinued Operations | Philadelphia | Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)		$ 4,000
2019 sales | Disposal Group, Not Discontinued Operations | Arizona | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		8.8		8.8
2019 sales | Disposal Group, Not Discontinued Operations | Southeastern PA | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		18		18
2019 sales | Disposal Group, Not Discontinued Operations | New Jersey | Acres of Developable Land
Property, Plant and Equipment [Line Items]
Acres of Developable Land (in acres) | a		68.4		68.4
2019 sales | Discontinued operations | Philadelphia
Property, Plant and Equipment [Line Items]
Debt Instrument, Interest Rate During Period	4.84%
Loss on debt extinguishment	$ 7,600
2019 sales | Discontinued operations | Arizona | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)				$ 11,500
2019 sales | Discontinued operations | Southeastern PA | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		5		5
Leaseable Square Feet (in sqft) | ft²		254,331		254,331
2019 sales | Discontinued operations | Southeastern PA | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)				$ 40,200
2019 sales | Discontinued operations | New Jersey | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)				$ 8,070
2019 sales | Discontinued operations | DC Metro | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		2		2
Leaseable Square Feet (in sqft) | ft²		437,234		437,234
2019 sales | Discontinued operations | DC Metro | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)				$ 154,250
2019 sales | Operating Segments | Disposal Group, Not Discontinued Operations | Carolinas/Richmond | Building and Building Improvements
Property, Plant and Equipment [Line Items]
Number of buildings (in buildings) | bldg		1		1
Leaseable Square Feet (in sqft) | ft²		136,000		136,000
2019 sales | Operating Segments | Disposal Group, Not Discontinued Operations | Carolinas/Richmond | Land, Buildings and Improvements
Property, Plant and Equipment [Line Items]
Gross Proceeds (in thousands)				$ 14,100

Real Estate Related Party (Deta

Real Estate Related Party (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019USD ($)	Sep. 30, 2019USD ($)
New Jersey | Equity Method Investee
Related Party Transaction [Line Items]
Ownership percentage of equity method investment	25.00%	25.00%
Land Improvements [Member] | Philadelphia | Vice President [Member] | sale of development rights [Member]
Related Party Transaction [Line Items]
Land sold to related party	$ 3.2	$ 3.2
2019 sales | Acres of Developable Land | Disposal Group, Not Discontinued Operations | New Jersey | Equity Method Investee | land sale to related party [Member]
Related Party Transaction [Line Items]
Land sold to related party		$ 4.1
2019 sales current quarter | Acres of Developable Land | Disposal Group, Not Discontinued Operations | New Jersey | Equity Method Investee | land sale to related party [Member]
Related Party Transaction [Line Items]
Land sold to related party	$ 4.1

Segment Information - Income St

Segment Information - Income Statement (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Revenue	$ 163,169,000	$ 161,286,000	$ 481,743,000	$ 498,944,000
Interest expense	(25,791,000)	(23,133,000)	(76,644,000)	(66,189,000)
Development service fee income	257,000	12,956,000	2,099,000	59,132,000
Development service fee expense	(168,000)	(12,924,000)	(1,848,000)	(120,799,000)
Depreciation and amortization expense	(43,972,000)	(41,004,000)	(130,402,000)	(120,586,000)
Impairment charges - real estate assets			(99,000)	(26,000,000)
Gain on property dispositions	15,168,000	2,002,000	21,125,000	54,705,000
Equity in earnings of unconsolidated joint ventures	1,776,000	6,766,000	10,966,000	20,958,000
General and administrative expense	(10,186,000)	(9,807,000)	(35,483,000)	(32,747,000)
Leasing cost	(3,082,000)	(2,610,000)	(9,608,000)	(8,189,000)
Other operating expense	(3,166,000)	(3,169,000)	(8,690,000)	(7,467,000)
Income taxes	(878,000)	(444,000)	(1,449,000)	(1,884,000)
Income from continuing operations	60,487,000	44,873,000	154,856,000	94,155,000
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Operating Segments
Segment Reporting Information [Line Items]
Revenue	171,410,000	172,223,000	513,416,000	513,797,000
Net operating income	124,748,000	123,032,000	371,208,000	368,123,000
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Revenue	0	18,000	(179,000)	(372,000)
Interest expense	(26,220,000)	(24,670,000)	(78,297,000)	(71,331,000)
Development service fee income	257,000	12,956,000	2,099,000	59,132,000
Development service fee expense	(168,000)	(12,924,000)	(1,848,000)	(120,799,000)
Depreciation and amortization expense	(32,279,000)	(32,243,000)	(97,642,000)	(97,576,000)
Impairment charges - real estate assets	0	0	(99,000)	(26,000,000)
Gain on property dispositions	15,168,000	2,002,000	21,125,000	54,705,000
Equity in earnings of unconsolidated joint ventures	1,776,000	6,766,000	10,966,000	20,958,000
General and administrative expense	(10,193,000)	(9,814,000)	(35,559,000)	(32,758,000)
Leasing cost	(3,082,000)	(2,610,000)	(9,608,000)	(8,189,000)
Other operating expense	(3,166,000)	(3,169,000)	(8,690,000)	(7,467,000)
Discontinued operations excluding (loss) gain on property dispositions	(4,951,000)	(14,320,000)	(18,553,000)	(39,842,000)
Income taxes	(811,000)	(329,000)	(1,635,000)	(1,539,000)
Other	(592,000)	196,000	1,389,000	(3,262,000)
Development service fee income | Segment Reconciling Items
Segment Reporting Information [Line Items]
Revenue	257,000	12,956,000	2,099,000	59,132,000
Discontinued operations | Segment Reconciling Items
Segment Reporting Information [Line Items]
Revenue	(8,498,000)	(23,911,000)	(33,593,000)	(73,613,000)
Carolinas/Richmond | Operating Segments | North America
Segment Reporting Information [Line Items]
Revenue	20,377,000	19,417,000	61,129,000	58,723,000
Net operating income	15,638,000	14,620,000	47,020,000	43,795,000
Chicago/Minneapolis | Operating Segments | North America
Segment Reporting Information [Line Items]
Revenue	17,479,000	17,274,000	52,299,000	50,414,000
Net operating income	10,902,000	10,564,000	33,294,000	31,271,000
Cincinnati/Columbus/Indianapolis | Operating Segments | North America
Segment Reporting Information [Line Items]
Revenue	4,792,000	4,245,000	13,822,000	13,613,000
Net operating income	3,262,000	2,749,000	9,186,000	9,099,000
Dallas | Operating Segments | North America
Segment Reporting Information [Line Items]
Revenue	5,953,000	5,537,000	17,252,000	14,300,000
Net operating income	4,035,000	3,666,000	11,848,000	9,274,000
Florida | Operating Segments | North America
Segment Reporting Information [Line Items]
Revenue	15,871,000	15,847,000	48,218,000	47,117,000
Net operating income	11,628,000	11,461,000	35,097,000	33,717,000
Houston | Operating Segments | North America
Segment Reporting Information [Line Items]
Revenue	19,103,000	16,561,000	51,831,000	48,514,000
Net operating income	12,377,000	9,676,000	32,159,000	28,714,000
Lehigh/Central PA | Operating Segments | North America
Segment Reporting Information [Line Items]
Revenue	38,878,000	39,188,000	118,588,000	115,799,000
Net operating income	29,902,000	29,406,000	89,639,000	86,085,000
Philadelphia | Operating Segments | North America
Segment Reporting Information [Line Items]
Revenue	9,779,000	10,598,000	32,043,000	33,659,000
Net operating income	7,876,000	7,947,000	25,583,000	28,211,000
Southern California | Operating Segments | North America
Segment Reporting Information [Line Items]
Revenue	10,510,000	7,914,000	30,660,000	22,226,000
Net operating income	8,200,000	6,496,000	23,524,000	17,675,000
United Kingdom | Operating Segments | United Kingdom
Segment Reporting Information [Line Items]
Revenue	5,900,000	3,523,000	17,857,000	11,579,000
Net operating income	5,421,000	3,234,000	16,131,000	10,662,000
Other | Operating Segments
Segment Reporting Information [Line Items]
Revenue	22,768,000	32,119,000	69,717,000	97,853,000
Net operating income	$ 15,507,000	$ 23,213,000	$ 47,727,000	$ 69,620,000

Segment Information - Total Ass

Segment Information - Total Assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Document Period End Date	Sep. 30, 2019
Assets	$ 7,338,732	$ 6,934,394
Operating Segments
Segment Reporting Information [Line Items]
Assets	6,701,430	6,737,720
Operating Segments | Other
Segment Reporting Information [Line Items]
Assets	1,062,447	1,153,518
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Assets	637,302	196,674
North America | Operating Segments | Carolinas/Richmond
Segment Reporting Information [Line Items]
Assets	516,811	525,041
North America | Operating Segments | Chicago/Minneapolis
Segment Reporting Information [Line Items]
Assets	597,557	591,792
North America | Operating Segments | Cincinnati/Columbus/Indianapolis
Segment Reporting Information [Line Items]
Assets	134,111	131,400
North America | Operating Segments | Dallas
Segment Reporting Information [Line Items]
Assets	306,463	261,538
North America | Operating Segments | Florida
Segment Reporting Information [Line Items]
Assets	550,623	547,232
North America | Operating Segments | Houston
Segment Reporting Information [Line Items]
Assets	608,761	568,756
North America | Operating Segments | Lehigh/Central PA
Segment Reporting Information [Line Items]
Assets	1,225,016	1,210,220
North America | Operating Segments | Philadelphia
Segment Reporting Information [Line Items]
Assets	540,972	624,373
North America | Operating Segments | Southern California
Segment Reporting Information [Line Items]
Assets	766,578	660,688
United Kingdom | Operating Segments | United Kingdom
Segment Reporting Information [Line Items]
Assets	$ 392,091	$ 463,162

Impairment and Disposal of Lo_4

Impairment and Disposal of Long-Lived Assets - Discontinued Operations (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)a	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)a	Sep. 30, 2018USD ($)	Sep. 30, 2019properties	Sep. 30, 2019bldg	Dec. 31, 2018bldg
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Income taxes	$ (878)	$ (444)	$ (1,449)	$ (1,884)
Loss on debt extinguishment			(7,618)	0
Gain on property dispositions	37,200	94,900	87,400	184,700
Income from discontinued operations	42,189	109,198	105,905	224,531
Noncontrolling interest - consolidated joint ventures	(3)	(232)	(170)	(1,010)
Income from discontinued operations available to common shareholders	41,273	106,430	103,315	218,887
Discontinued operations
Discontined Operations Income Statement [Line Items]
Capital expenditures	100	10,800	3,600	38,300
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues	8,498	23,911	33,593	73,613
Operating expenses	(3,117)	(5,329)	(10,903)	(17,276)
Depreciation and amortization	0	(2,666)	(2,129)	(11,138)
Impairment charges - real estate assets	(7,190)	0	(21,482)	0
Interest and other income (expense)	4	(31)	(57)	(132)
Income taxes	(5)	(28)	(298)	(83)
Loss on debt extinguishment	0	0	(7,618)	0
Interest expense	(429)	(1,537)	(1,653)	(5,142)
Gain on property dispositions	44,428	94,878	116,452	184,689
Income from discontinued operations	42,189	109,198	105,905	224,531
Noncontrolling interest - operating partnership	(916)	(2,544)	(2,404)	(5,232)
Noncontrolling interest - consolidated joint ventures	0	(224)	(186)	(412)
Income from discontinued operations available to common shareholders	$ 41,273	$ 106,430	$ 103,315	$ 218,887
Properties included in discontinued operations, held for sale
Discontined Operations Income Statement [Line Items]
Number of buildings (in buildings) | bldg						9
Properties included in discontinued operations, held for sale | Chicago/Minneapolis
Discontined Operations Income Statement [Line Items]
Number of buildings (in buildings) | bldg						1
Properties included in discontinued operations, held for sale | Philadelphia
Discontined Operations Income Statement [Line Items]
Number of buildings (in buildings) | bldg						6
Properties included in discontinued operations, held for sale | United Kingdom
Discontined Operations Income Statement [Line Items]
Number of buildings (in buildings) | bldg						2
Properties included in discontinued operations, sold
Discontined Operations Income Statement [Line Items]
Number of buildings (in buildings) | bldg						13	37
Properties included in discontinued operations, total
Discontined Operations Income Statement [Line Items]
Number of buildings (in buildings) | bldg						59
Properties included in continuing operations, held for sale
Discontined Operations Income Statement [Line Items]
Number of buildings (in buildings) | bldg						1
Properties included in continuing operations, sold
Discontined Operations Income Statement [Line Items]
Number of buildings (in buildings) | bldg						1	2
Properties included in continuing operations, total
Discontined Operations Income Statement [Line Items]
Number of buildings (in buildings) | bldg						4
Properties sold or classified as held for sale, held for sale
Discontined Operations Income Statement [Line Items]
Number of buildings (in buildings)					3	10
Acres of Developable Land (in acres) | a	74.4		74.4
Properties sold or classified as held for sale, sold
Discontined Operations Income Statement [Line Items]
Number of buildings (in buildings) | bldg						14	39
Properties sold or classified as held for sale, total
Discontined Operations Income Statement [Line Items]
Number of buildings (in buildings) | bldg						63

Impairment and Disposal of Lo_5

Impairment and Disposal of Long-Lived Assets - Assets Held for Sale (Details) $ in Thousands	Sep. 30, 2019USD ($)	Sep. 30, 2019a	Sep. 30, 2019properties	Sep. 30, 2019bldg	Dec. 31, 2018USD ($)
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Total assets held for sale	$ 226,504				$ 502,207
Liabilities held for sale	15,939				21,131
Included in Continuing Operations
Balance Sheet Disclosures by Disposal Groups [Line Items]
Number of buildings (in buildings) | bldg				1
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Land and land improvements	613				1,301
Buildings and improvements	8,541				5,638
Disposal Group, Including Discontinued Operation, Development in Progress	0				0
Land held for development	19,420				26,253
Accumulated depreciation	(3,745)				(1,546)
Deferred financing and leasing costs, net	717				58
Other assets	756				164
Total assets held for sale	26,302				31,868
Liabilities held for sale	419				141
Included in Discontinued Operations
Balance Sheet Disclosures by Disposal Groups [Line Items]
Number of buildings (in buildings) | bldg				9
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Land and land improvements	19,210				113,080
Buildings and improvements	174,595				384,737
Disposal Group, Including Discontinued Operation, Development in Progress	10,108				9,597
Land held for development	0				0
Accumulated depreciation	(21,592)				(70,242)
Deferred financing and leasing costs, net	7,910				13,697
Other assets	9,971				19,470
Total assets held for sale	200,202				470,339
Liabilities held for sale	15,520				20,990
Total
Balance Sheet Disclosures by Disposal Groups [Line Items]
Acres of Developable Land (in acres) | a		74.4
Number of buildings (in buildings)			3	10
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Land and land improvements	19,823				114,381
Buildings and improvements	183,136				390,375
Disposal Group, Including Discontinued Operation, Development in Progress	10,108				9,597
Land held for development	19,420				26,253
Accumulated depreciation	(25,337)				(71,788)
Deferred financing and leasing costs, net	8,627				13,755
Other assets	10,727				19,634
Total assets held for sale	226,504				502,207
Liabilities held for sale	$ 15,939				$ 21,131

Impairment and Disposal of Lo_6

Impairment and Disposal of Long-Lived Assets - Impairment Charges - Real Estate Assets (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charges - real estate assets		$ 99,000	$ 26,000,000
Valuation adjustment	$ 0	0
Office Building | DC Metro
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charges - real estate assets	$ 7,200,000	$ 21,600,000
Land | Philadelphia
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charges - real estate assets			$ 26,000,000

Noncontrolling Interests of t_2

Noncontrolling Interests of the Trust- Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Redeemable Noncontrolling Interest [Line Items]
Limited Partners' common units outstanding	3,500,000	3,520,205
Liberty Property Limited Partnership
Redeemable Noncontrolling Interest [Line Items]
Limited Partners' common units outstanding	3,500,000	3,520,205
Market value of common units based on closing price	$ 179.3

Limited Partners' Equity and _2

Limited Partners' Equity and Noncontrolling Interest of the Operating Partnership (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Limited Partners' Capital Account [Line Items]
Limited Partners' common units outstanding	3,500,000	3,520,205
Liberty Property Limited Partnership
Limited Partners' Capital Account [Line Items]
Limited Partners' common units outstanding	3,500,000	3,520,205
Market value of common units based on closing price	$ 179.3

Noncontrolling Interest - Ope_3

Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Temporary Equity [Line Items]
AMOUNT	$ 5,337	$ 5,337	$ 7,537	$ 7,537	$ 7,537	$ 7,537
Preferred units redeemed (in shares)	88,000
Preferred units redeemed, value	$ 2,200
Series I-2
Temporary Equity [Line Items]
UNITS	213,483		301,483
LIQUIDATION PREFERENCE (in usd per share)	$ 25
DIVIDEND RATE	6.25%

Indebtedness (Details)

Indebtedness (Details) - 4.375% Senior Unsecured Notes	Jan. 31, 2019USD ($)
Debt Instrument [Line Items]
Debt issued, face amount	$ 350,000,000
Interest Rate	4.375%

Disclosure of Fair Value of F_4

Disclosure of Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage loans, net	$ 297,326	$ 395,202
Unsecured Debt	2,633,941	2,285,698
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage loans, net	297,326	395,202
Unsecured Debt	2,633,941	2,285,698
Long-term Debt [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage Loans | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	304,689	397,167
Long-term Debt [Member] | Fair Value, Inputs, Level 3 [Member] | Unsecured Notes | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	$ 2,821,931	$ 2,295,699

Unconsolidated Joint Ventures -

Unconsolidated Joint Ventures - Liberty Property 18th & Arch LP and Liberty Property 18th & Arch, Hotel, LP (Details) $ in Thousands, ft² in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)investment	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)investment	Sep. 30, 2018USD ($)	Dec. 31, 2018USD ($)	Jun. 30, 2014ft²roominvestmentstory
Schedule of Equity Method Investments [Line Items]
Investments in and advances to unconsolidated joint ventures	$ 347,880		$ 347,880		$ 350,981
Philadelphia | Liberty Property 18th & Arch
Schedule of Equity Method Investments [Line Items]
Number of equity method investments (in investments) | investment	2		2			2
Anticipated Aggregate Investment	$ 968,000		$ 968,000
Investments in and advances to unconsolidated joint ventures	193,700		193,700
Philadelphia | Construction in Progress | Liberty Property 18th & Arch
Schedule of Equity Method Investments [Line Items]
Number of stories in a high-rise building (in stories) | story						60
Number of hotel rooms (in rooms) | room						219
Leaseable square feet (in sqft) | ft²						1.3
Other Liabilities | Philadelphia | Liberty Property 18th & Arch | Guarantee Obligations
Schedule of Equity Method Investments [Line Items]
Loss contingency accrual	29,600	$ 69,300	29,600	$ 69,300	$ 67,300
Accounts Payable [Member] | Philadelphia | Liberty Property 18th & Arch | Guarantee Obligations
Schedule of Equity Method Investments [Line Items]
Retention Payable	24,000		24,000
Equity Method Investee | Liberty Property 18th & Arch | Philadelphia
Schedule of Equity Method Investments [Line Items]
Net operating income	$ 0	$ 0	$ 0	$ (61,800)

Unconsolidated Joint Ventures_2

Unconsolidated Joint Ventures - Cambridge Medipark Ltd (Details) - Cambridge Medipark Ltd - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Schedule of Equity Method Investments [Line Items]
Ownership percentage of equity method investment	50.00%		50.00%
Leaseholds and Leasehold Improvements | Other Income | Disposal Group, Not Discontinued Operations
Schedule of Equity Method Investments [Line Items]
Gain on sale of leasehold interests	$ 112,000	$ 1,200,000	$ 1,100,000	$ 5,000,000

Unconsolidated Joint Ventures_3

Unconsolidated Joint Ventures -Liberty Washington, LP (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018
Schedule of Equity Method Investments [Line Items]
Impairment charges - real estate assets		$ 99	$ 26,000
DC Metro | Liberty Washington, LP [Member] | Discontinued operations
Schedule of Equity Method Investments [Line Items]
Impairment charges - real estate assets	$ 10,300	26,700
DC Metro | Liberty Property Limited Partnership | Other Investments | Equity Method Investee | Liberty Washington, LP [Member]
Schedule of Equity Method Investments [Line Items]
Impairment charges - real estate assets	$ 2,600	$ 6,700

Derivative Instruments (Details

Derivative Instruments (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2019USD ($)	Sep. 30, 2019USD ($)contract	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)contract	Sep. 30, 2018USD ($)	Dec. 31, 2018USD ($)contract
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense		$ 25,791	$ 23,133	$ 76,644	$ 66,189
Interest Rate Derivatives [Abstract]
Number of interest rate swaps | contract		2		2
Fair value		$ 345		$ 345		$ 4,649
Reclassification during next 12 months		500		500
Termination value		300		300
Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense		25,791	23,133	76,644	66,189
Interest Rate Swap
Interest Rate Derivatives [Abstract]
Aggregate notional amount		65,100		65,100		$ 66,800
Interest Rate Swap | Other Comprehensive Income (Loss) | Designated as Hedging Instrument | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain related to the effective portion recognized in other comprehensive (loss) income		13	$ 69	424	$ 619
Interest Rate Lock Commitments
Interest Rate Derivatives [Abstract]
Number of interest rate swaps | contract						2
Aggregate notional amount						$ 200,000
Gain (loss) on contract termination	$ 5,700
Interest Rate Lock Agreement A
Interest Rate Derivatives [Abstract]
Aggregate notional amount						100,000
Derivative, gain on derivative						$ 2,400
Number of derivative instruments expired | contract						1
Interest Rate Lock Agreement B
Interest Rate Derivatives [Abstract]
Aggregate notional amount	100,000
Derivative, gain on derivative	$ 3,300
Other Liabilities | Interest Rate Swap
Interest Rate Derivatives [Abstract]
Fair value		345		345		$ 677
Other Liabilities | Interest Rate Lock Commitments
Interest Rate Derivatives [Abstract]
Fair value		$ 0		$ 0		$ 3,972

Commitments and Contingencies -

Commitments and Contingencies - Legal Matters (Details)	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Number of legal claims	0

Commitments and Contingencies_2

Commitments and Contingencies - Other (Details) $ in Thousands, ft² in Millions	Sep. 30, 2019USD ($)ft²propertiesbldginvestment	Dec. 31, 2018USD ($)	Jun. 30, 2014ft²investment
Loss Contingencies [Line Items]
Letters of credit outstanding	$ 8,900
Development in progress	323,790	$ 462,572
Acres of developable land | Land Purchases
Loss Contingencies [Line Items]
Remaining amount committed to future acquisitions	53,100
Supply Commitment | Leasehold Improvements
Loss Contingencies [Line Items]
Remaining maximum amount committed for tenant improvements	$ 19,500
Supply Commitment | Construction in Progress
Loss Contingencies [Line Items]
Leaseable square feet (in sqft) | ft²	4.7
Number of buildings (in buildings) | bldg	22
Total anticipated development cost	$ 463,900
Development in progress	323,800
Deferred leasing costs in development	3,200
Remaining amount committed or obligated to pay	$ 1,000
Supply Commitment | Construction in Progress | Equity Method Investments
Loss Contingencies [Line Items]
Number of buildings (in buildings) | properties	3
Supply Commitment | Land, Buildings and Improvements
Loss Contingencies [Line Items]
Remaining amount committed or obligated to pay	$ 20,300
Philadelphia | Liberty Property 18th & Arch
Loss Contingencies [Line Items]
Number of equity method investments (in investments) | investment	2		2
Total anticipated development cost	$ 968,000
Philadelphia | Liberty Property 18th & Arch | Construction in Progress
Loss Contingencies [Line Items]
Leaseable square feet (in sqft) | ft²			1.3
American Water Works, Inc | Supply Commitment | Building and Building Improvements
Loss Contingencies [Line Items]
Other commitment	$ 35,600

Supplemental Disclosure to St_3

Supplemental Disclosure to Statements of Cash Flows - Schedule of Supplemental Disclosures (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Continuing Operations
Other Significant Noncash Transactions [Line Items]
Write off of fully depreciated property and deferred costs	$ 2,218	$ 7,197
Write of depreciated property and deferred costs due to sale and related debt repayment	1,642	20,273
Change in accrued development capital expenditures	(4,436)	12,361
Unrealized (loss) gain on cash flow hedge, non cash transaction	(1,887)	493
Capitalized equity-based compensation	915	727
Discontinued operations
Other Significant Noncash Transactions [Line Items]
Write off of fully depreciated property and deferred costs	0	11,789
Write of depreciated property and deferred costs due to sale and related debt repayment	51,455	99,072
Change in accrued development capital expenditures	$ 0	$ (4,628)

Supplemental Disclosure to St_4

Supplemental Disclosure to Statements of Cash Flows - Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Cash and Cash Equivalents, at Carrying Value [Abstract]
Cash and cash equivalents	$ 514,882	$ 84,923	$ 17,770	$ 11,882
Restricted cash	14,006	10,899	13,371	13,803
Cash, cash equivalents and restricted cash	$ 528,888	$ 95,822	$ 31,141	$ 25,685

Subsequent Events (Details)

Subsequent Events (Details) $ in Thousands	Oct. 12, 2019USD ($)	Oct. 28, 2019	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)
Subsequent Event [Line Items]
Loss on debt extinguishment			$ 7,618	$ 0
Subsequent Event [Member]
Subsequent Event [Line Items]
Loss on debt extinguishment	$ 9,000
Unsecured Notes | Subsequent Event [Member]
Subsequent Event [Line Items]
Repayments of unsecured notes	$ 350,000
Interest Rate	4.75%
Prologis Inc. [Member] | Common shares | Liberty Property Trust [Member] | Subsequent Event [Member]
The Proposed Merger with Prologis, Inc. [Abstract]
Conversion ratio		0.675
Prologis Inc. [Member] | Common Units | Liberty Property Limited Partnership | Subsequent Event [Member]
The Proposed Merger with Prologis, Inc. [Abstract]
Conversion ratio		0.675