Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
ASSETS
Land and land improvements	$ 854,972	$ 855,213
Building and improvements	4,117,093	4,109,783
Less accumulated depreciation	(1,088,301)	(1,058,283)
Operating real estate	3,883,764	3,906,713
Development in progress	138,634	88,848
Land held for development	218,926	219,375
Net real estate	4,241,324	4,214,936
Cash and cash equivalents	27,650	18,204
Restricted cash	39,188	63,659
Accounts receivable	9,210	8,192
Deferred rent receivable	104,502	103,002
Deferred financing and leasing costs, net of accumulated amortization (2012, $128,303; 2011, $123,822)	130,843	130,160
Investments in and advances to unconsolidated joint ventures	174,651	174,687
Assets held for sale	197,737	200,647
Prepaid expenses and other assets	90,189	76,186
Total assets	5,015,294	4,989,673
LIABILITIES
Mortgage loans	282,716	290,819
Unsecured notes	1,792,643	1,792,643
Credit facility	293,300	139,400
Accounts payable	32,310	23,418
Accrued interest	33,036	24,147
Dividend and distributions payable	57,393	56,958
Other liabilities	177,590	194,995
Total liabilities	2,668,988	2,522,380
Noncontrolling Interest - operating partnership - 301,483 preferred units outstanding as of March 31, 2012 and December 31, 2011	7,537	7,537
EQUITY
Common shares of beneficial interest, $.001 par value, 183,987,000 shares authorized; 118,264,957 (includes 1,249,909 in treasury) and 117,352,353 (includes 1,249,909 in treasury) shares issued and outstanding as of March 31, 2012 and December 31, 2011, respectively	118	117
Additional paid-in capital	2,637,861	2,617,355
Accumulated other comprehensive loss	1,815	(429)
Distributions in excess of net income	(479,995)	(461,498)
Common shares in treasury, at cost, 1,249,909 shares as of March 31, 2012 and December 31, 2011	(51,951)	(51,951)
Total Liberty Property Trust shareholders' equity	2,107,848	2,103,594
Noncontrolling interest - operating partnership
Noncontrolling interest - consolidated joint ventures	3,775	3,775
Total equity	2,338,769	2,459,756
Total liabilities, noncontrolling interest - operating partnership and equity	5,015,294	4,989,673
3,808,746 common units outstanding as of March 31, 2012 and December 31, 2011, respectively
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnerships	63,920	64,428
5,290,000 and 9,740,000 preferred units outstanding as of March 31, 2012 and December 31, 2011, respectively
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnerships	163,226	287,959
Liberty Property Limited Partnership [Member]
ASSETS
Land and land improvements	854,972	855,213
Building and improvements	4,117,093	4,109,783
Less accumulated depreciation	(1,088,301)	(1,058,283)
Operating real estate	3,883,764	3,906,713
Development in progress	138,634	88,848
Land held for development	218,926	219,375
Net real estate	4,241,324	4,214,936
Cash and cash equivalents	27,650	18,204
Restricted cash	39,188	63,659
Accounts receivable	9,210	8,192
Deferred rent receivable	104,502	103,002
Deferred financing and leasing costs, net of accumulated amortization (2012, $128,303; 2011, $123,822)	130,843	130,160
Investments in and advances to unconsolidated joint ventures	174,651	174,687
Assets held for sale	197,737	200,647
Prepaid expenses and other assets	90,189	76,186
Total assets	5,015,294	4,989,673
LIABILITIES
Mortgage loans	282,716	290,819
Unsecured notes	1,792,643	1,792,643
Credit facility	293,300	139,400
Accounts payable	32,310	23,418
Accrued interest	33,036	24,147
Dividend and distributions payable	57,393	56,958
Other liabilities	177,590	194,995
Total liabilities	2,668,988	2,522,380
Noncontrolling Interest - operating partnership - 301,483 preferred units outstanding as of March 31, 2012 and December 31, 2011	7,537	7,537
EQUITY
General patner's equity - 117,015,048 (net of 1,249,909 treasury units) and 116,102,444 (net of 1,249,909 treasury units) common units outstanding as of March 31, 2012 and December 31, 2011, respectively	2,107,848	2,103,594
Noncontrolling interest - operating partnership
Noncontrolling interest - consolidated joint ventures	3,775	3,775
Total equity	2,338,769	2,459,756
Total liabilities, noncontrolling interest - operating partnership and equity	5,015,294	4,989,673
Liberty Property Limited Partnership [Member] | 3,808,746 common units outstanding as of March 31, 2012 and December 31, 2011, respectively
EQUITY
Limited partners' equity	63,920	64,428
Liberty Property Limited Partnership [Member] | 5,290,000 and 9,740,000 preferred units outstanding as of March 31, 2012 and December 31, 2011, respectively
EQUITY
Limited partners' equity	$ 163,226	$ 287,959