Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
ASSETS
Land and land improvements	$ 861,373	$ 855,213
Building and improvements	4,146,819	4,109,783
Less accumulated depreciation	(1,116,593)	(1,058,283)
Operating real estate	3,891,599	3,906,713
Development in progress	198,472	88,848
Land held for development	222,090	219,375
Net real estate	4,312,161	4,214,936
Cash and cash equivalents	154,122	18,204
Restricted cash	39,604	63,659
Accounts receivable	12,424	8,192
Deferred rent receivable	106,243	103,002
Deferred financing and leasing costs, net of accumulated amortization (2012, $133,448; 2011, $123,822)	133,150	130,160
Investments in and advances to unconsolidated joint ventures	173,336	174,687
Assets held for sale	0	200,647
Prepaid expenses and other assets	77,272	76,186
Total assets	5,008,312	4,989,673
LIABILITIES
Mortgage loans	281,170	290,819
Unsecured notes	2,192,643	1,792,643
Credit facility	0	139,400
Accounts payable	35,600	23,418
Accrued interest	25,196	24,147
Dividend and distributions payable	57,610	56,958
Other liabilities	176,656	194,995
Total liabilities	2,768,875	2,522,380
Noncontrolling Interest - operating partnership - 301,483 preferred units outstanding as of June 30, 2012 and December 31, 2011	7,537	7,537
EQUITY
Common shares of beneficial interest, $.001 par value, 183,987,000 shares authorized; 118,794,699 (includes 1,249,909 in treasury) and 117,352,353 (includes 1,249,909 in treasury) shares issued and outstanding as of June 30, 2012 and December 31, 2011, respectively	119	117
Additional paid-in capital	2,656,174	2,617,355
Accumulated other comprehensive loss	346	(429)
Distributions in excess of net income	(501,719)	(461,498)
Common shares in treasury, at cost, 1,249,909 shares as of June 30, 2012 and December 31, 2011	(51,951)	(51,951)
Total Liberty Property Trust shareholders' equity	2,102,969	2,103,594
Noncontrolling interest - operating partnership
Noncontrolling interest - consolidated joint ventures	3,775	3,775
Total equity	2,231,900	2,459,756
Total liabilities, noncontrolling interest - operating partnership and equity	5,008,312	4,989,673
3,740,246 and 3,808,746 common units outstanding as of June 30, 2012 and December 31, 2011, respectively
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnerships	61,891	64,428
1,290,000 and 9,740,000 preferred units outstanding as of June 30, 2012 and December 31, 2011, respectively
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnerships	63,265	287,959
Liberty Property Limited Partnership [Member]
ASSETS
Land and land improvements	861,373	855,213
Building and improvements	4,146,819	4,109,783
Less accumulated depreciation	(1,116,593)	(1,058,283)
Operating real estate	3,891,599	3,906,713
Development in progress	198,472	88,848
Land held for development	222,090	219,375
Net real estate	4,312,161	4,214,936
Cash and cash equivalents	154,122	18,204
Restricted cash	39,604	63,659
Accounts receivable	12,424	8,192
Deferred rent receivable	106,243	103,002
Deferred financing and leasing costs, net of accumulated amortization (2012, $133,448; 2011, $123,822)	133,150	130,160
Investments in and advances to unconsolidated joint ventures	173,336	174,687
Assets held for sale	0	200,647
Prepaid expenses and other assets	77,272	76,186
Total assets	5,008,312	4,989,673
LIABILITIES
Mortgage loans	281,170	290,819
Unsecured notes	2,192,643	1,792,643
Credit facility	0	139,400
Accounts payable	35,600	23,418
Accrued interest	25,196	24,147
Dividend and distributions payable	57,610	56,958
Other liabilities	176,656	194,995
Total liabilities	2,768,875	2,522,380
Noncontrolling Interest - operating partnership - 301,483 preferred units outstanding as of June 30, 2012 and December 31, 2011	7,537	7,537
EQUITY
General patner's equity - 117,544,790 (net of 1,249,909 treasury units) and 116,102,444 (net of 1,249,909 treasury units) common units outstanding as of June 30, 2012 and December 31, 2011, respectively	2,102,969	2,103,594
Noncontrolling interest - operating partnership
Noncontrolling interest - consolidated joint ventures	3,775	3,775
Total equity	2,231,900	2,459,756
Total liabilities, noncontrolling interest - operating partnership and equity	5,008,312	4,989,673
Liberty Property Limited Partnership [Member] | 3,740,246 and 3,808,746 common units outstanding as of June 30, 2012 and December 31, 2011, respectively
EQUITY
Limited partners' equity	61,891	64,428
Liberty Property Limited Partnership [Member] | 1,290,000 and 9,740,000 preferred units outstanding as of June 30, 2012 and December 31, 2011, respectively
EQUITY
Limited partners' equity	$ 63,265	$ 287,959