Consolidated Balance Sheets (USD $)	Dec. 31, 2012	Dec. 31, 2011
ASSETS
Land and land improvements	$ 900,501,000	$ 852,785,000
Building and improvements	4,353,433,000	4,092,056,000
Less accumulated depreciation	(1,170,030,000)	(1,047,336,000)
Operating real estate	4,083,904,000	3,897,505,000
Development in progress	248,602,000	88,848,000
Land held for development	258,324,000	219,375,000
Net real estate	4,590,830,000	4,205,728,000
Cash and cash equivalents	38,356,000	18,204,000
Restricted cash	33,147,000	63,659,000
Accounts receivable	8,988,000	8,192,000
Deferred rent receivable	108,628,000	102,613,000
Deferred financing and leasing costs, net	141,245,000	129,614,000
Investments in and advances to unconsolidated joint ventures	169,021,000	174,687,000
Assets held for sale	0	210,790,000
Prepaid expenses and other assets	87,756,000	76,186,000
Total assets	5,177,971,000	4,989,673,000
LIABILITIES
Mortgage Loans	302,855,000	290,819,000
Unsecured notes	2,262,543,000	1,792,643,000
Credit facility	92,000,000	139,400,000
Accounts payable	31,058,000	23,418,000
Accrued interest	20,164,000	24,147,000
Dividend and distributions payable	58,038,000	56,958,000
Other liabilities	185,956,000	194,995,000
Total liabilities	2,952,614,000	2,522,380,000
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of December 31, 2012 and December 31, 2011	7,537,000	7,537,000
EQUITY
Common shares of beneficial interest, $.001 par value, 183,987,000 shares authorized; 119,720,776 (includes 1,249,909 in treasury) and 117,352,353 (includes 1,249,909 in treasury) shares issued and outstanding as of December 31, 2012 and December 31, 2011, respectively	119,000	117,000
Additional paid-in capital	2,687,701,000	2,617,355,000
Accumulated other comprehensive income (loss)	2,900,000	(429,000)
Distributions in excess of net income	(547,757,000)	(461,498,000)
Common shares in treasury, at cost, 1,249,909 shares as of December 31, 2012 and 2011	(51,951,000)	(51,951,000)
Total Liberty Property Trust shareholders' equity	2,091,012,000	2,103,594,000
Noncontrolling interest - operating partnership
Noncontrolling interest - consolidated joint ventures	3,321,000	3,775,000
Total equity	2,217,820,000	2,459,756,000
Total liabilities, noncontrolling interest - operating partnership and equity	5,177,971,000	4,989,673,000
Limited Partner's Common Units [Member]
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnerships	60,223,000	64,428,000
Limited Partner's Preferred Units [Member]
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnerships	63,264,000	287,959,000
Liberty Property Limited Partnership [Member]
ASSETS
Land and land improvements	900,501,000	852,785,000
Building and improvements	4,353,433,000	4,092,056,000
Less accumulated depreciation	(1,170,030,000)	(1,047,336,000)
Operating real estate	4,083,904,000	3,897,505,000
Development in progress	248,602,000	88,848,000
Land held for development	258,324,000	219,375,000
Net real estate	4,590,830,000	4,205,728,000
Cash and cash equivalents	38,356,000	18,204,000
Restricted cash	33,147,000	63,659,000
Accounts receivable	8,988,000	8,192,000
Deferred rent receivable	108,628,000	102,613,000
Deferred financing and leasing costs, net	141,245,000	129,614,000
Investments in and advances to unconsolidated joint ventures	169,021,000	174,687,000
Assets held for sale	0	210,790,000
Prepaid expenses and other assets	87,756,000	76,186,000
Total assets	5,177,971,000	4,989,673,000
LIABILITIES
Mortgage Loans	302,855,000	290,819,000
Unsecured notes	2,262,543,000	1,792,643,000
Credit facility	92,000,000	139,400,000
Accounts payable	31,058,000	23,418,000
Accrued interest	20,164,000	24,147,000
Dividend and distributions payable	58,038,000	56,958,000
Other liabilities	185,956,000	194,995,000
Total liabilities	2,952,614,000	2,522,380,000
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of December 31, 2012 and December 31, 2011	7,537,000	7,537,000
EQUITY
General partner’s equity	2,091,012,000	2,103,594,000
Noncontrolling interest - operating partnership
Noncontrolling interest - consolidated joint ventures	3,321,000	3,775,000
Total equity	2,217,820,000	2,459,756,000
Total liabilities, noncontrolling interest - operating partnership and equity	5,177,971,000	4,989,673,000
Liberty Property Limited Partnership [Member] | Limited Partner's Common Units [Member]
EQUITY
Limited partners’ equity	60,223,000	64,428,000
Liberty Property Limited Partnership [Member] | Limited Partner's Preferred Units [Member]
EQUITY
Limited partners’ equity	$ 63,264,000	$ 287,959,000