Consolidated Balance Sheets (USD $)	Dec. 31, 2011	Dec. 31, 2010
ASSETS
Land and land improvements	$ 856,783,000	$ 801,271,000
Building and improvements	4,117,179,000	3,902,891,000
Less accumulated depreciation	(1,062,230,000)	(938,044,000)
Operating real estate	3,911,732,000	3,766,118,000
Development in progress	88,848,000	0
Land held for development	219,375,000	203,811,000
Net real estate	4,219,955,000	3,969,929,000
Cash and cash equivalents	18,204,000	108,409,000
Restricted cash	63,659,000	49,526,000
Accounts receivable	8,192,000	6,898,000
Deferred rent receivable	103,008,000	99,779,000
Deferred financing and leasing costs, net	130,210,000	128,536,000
Investments in and advances to unconsolidated joint ventures	174,687,000	171,916,000
Assets held for sale	195,572,000	456,181,000
Prepaid expenses and other assets	76,186,000	73,625,000
Total assets	4,989,673,000	5,064,799,000
LIABILITIES
Mortgage loans	290,819,000	320,679,000
Unsecured notes	1,792,643,000	2,039,143,000
Credit facility	139,400,000	0
Accounts payable	23,418,000	23,652,000
Accrued interest	24,147,000	29,821,000
Dividend and distributions payable	56,958,000	56,149,000
Other liabilities	194,995,000	156,803,000
Total liabilities	2,522,380,000	2,626,247,000
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of December 31, 2011	7,537,000	0
EQUITY
Common shares of beneficial interest, $.001 par value, 183,987,000 shares authorized; 117,352,353 (includes 1,249,909 in treasury) and 115,530,608 (includes 1,249,909 in treasury) shares issued and outstanding as of December 31, 2011 and 2010, respectively	117,000	116,000
Additional paid-in capital	2,617,355,000	2,560,193,000
Accumulated other comprehensive loss	(429,000)	(155,000)
Distributions in excess of net income	(461,498,000)	(426,017,000)
Common shares in treasury, at cost, 1,249,909 shares as of December 31, 2011 and December 31, 2010	(51,951,000)	(51,951,000)
Total Liberty Property Trust shareholders' equity	2,103,594,000	2,082,186,000
Noncontrolling interest - operating partnership
Noncontrolling interest - consolidated joint ventures	3,775,000	786,000
Total equity	2,459,756,000	2,438,552,000
Total liabilities and equity	4,989,673,000	5,064,799,000
Limited Partner's Common Units [Member]
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnerships	64,428,000	67,621,000
Limited Partner's Preferred Units [Member]
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnerships	287,959,000	287,959,000
Liberty Property Limited Partnership [Member]
ASSETS
Land and land improvements	856,783,000	801,271,000
Building and improvements	4,117,179,000	3,902,891,000
Less accumulated depreciation	(1,062,230,000)	(938,044,000)
Operating real estate	3,911,732,000	3,766,118,000
Development in progress	88,848,000	0
Land held for development	219,375,000	203,811,000
Net real estate	4,219,955,000	3,969,929,000
Cash and cash equivalents	18,204,000	108,409,000
Restricted cash	63,659,000	49,526,000
Accounts receivable	8,192,000	6,898,000
Deferred rent receivable	103,008,000	99,779,000
Deferred financing and leasing costs, net	130,210,000	128,536,000
Investments in and advances to unconsolidated joint ventures	174,687,000	171,916,000
Assets held for sale	195,572,000	456,181,000
Prepaid expenses and other assets	76,186,000	73,625,000
Total assets	4,989,673,000	5,064,799,000
LIABILITIES
Mortgage loans	290,819,000	320,679,000
Unsecured notes	1,792,643,000	2,039,143,000
Credit facility	139,400,000	0
Accounts payable	23,418,000	23,652,000
Accrued interest	24,147,000	29,821,000
Dividend and distributions payable	56,958,000	56,149,000
Other liabilities	194,995,000	156,803,000
Total liabilities	2,522,380,000	2,626,247,000
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of December 31, 2011	7,537,000	0
EQUITY
General Partners' Capital Account	2,103,594,000	2,082,186,000
Noncontrolling interest - operating partnership
Noncontrolling interest - consolidated joint ventures	3,775,000	786,000
Total equity	2,459,756,000	2,438,552,000
Total liabilities and equity	4,989,673,000	5,064,799,000
Liberty Property Limited Partnership [Member] | Limited Partner's Common Units [Member]
EQUITY
Limited partners' equity	64,428,000	67,621,000
Liberty Property Limited Partnership [Member] | Limited Partner's Preferred Units [Member]
EQUITY
Limited partners' equity	$ 287,959,000	$ 287,959,000