Consolidated Balance Sheets (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
ASSETS
Land and land improvements	$ 838,730	$ 833,827
Building and improvements	4,179,856	4,136,214
Less accumulated depreciation	(1,070,428)	(1,001,737)
Operating real estate	3,948,158	3,968,304
Development in progress	11,829
Land held for development	210,605	209,253
Net real estate	4,170,592	4,177,557
Cash and cash equivalents	49,895	108,409
Restricted cash	50,151	49,526
Accounts receivable	7,750	6,898
Deferred rent receivable	106,851	103,336
Deferred financing and leasing costs, net of accumulated amortization (2011, $120,290; 2010, $115,118)	131,047	134,419
Investments in and advances to unconsolidated joint ventures	175,472	171,916
Assets held for sale	41,533	239,113
Prepaid expenses and other assets	113,080	73,625
Total assets	4,846,371	5,064,799
LIABILITIES
Mortgage loans	293,702	320,679
Unsecured notes	1,792,643	2,039,143
Credit facility	33,000
Accounts payable	28,595	23,652
Accrued interest	24,375	29,821
Dividend and distributions payable	56,632	56,149
Other liabilities	141,959	156,803
Total liabilities	2,370,906	2,626,247
EQUITY
Common shares of beneficial interest, $.001 par value, 183,987,000 shares authorized; 116,575,289 (includes 1,249,909 in treasury) and 115,530,608 (includes 1,249,909 in treasury) shares issued and outstanding as of June 30, 2011 and December 31, 2010, respectively	117	116
Additional paid-in capital	2,591,408	2,560,193
Accumulated other comprehensive income (loss)	1,956	(155)
Distributions in excess of net income	(421,507)	(426,017)
Common shares in treasury, at cost, 1,249,909 shares as of June 30, 2011 and December 31, 2010	(51,951)	(51,951)
Total Liberty Property Trust shareholders' equity	2,120,023	2,082,186
Limited partners' equity
Noncontrolling interest - consolidated joint ventures	328	786
Total equity	2,475,465	2,438,552
Total liabilities and equity	4,846,371	5,064,799
Liberty Property Limited Partnership [Member] | Limited Partner's Common Units [Member]
Limited partners' equity
Limited partners' equity	67,155	67,621
Limited Partner's Common Units [Member]
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnership	67,155	67,621
Liberty Property Limited Partnership [Member] | Limited Partner's Preferred Units [Member]
Limited partners' equity
Limited partners' equity	287,959	287,959
Limited Partner's Preferred Units [Member]
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnership	287,959	287,959
Liberty Property Limited Partnership [Member]
ASSETS
Land and land improvements	838,730	833,827
Building and improvements	4,179,856	4,136,214
Less accumulated depreciation	(1,070,428)	(1,001,737)
Operating real estate	3,948,158	3,968,304
Development in progress	11,829
Land held for development	210,605	209,253
Net real estate	4,170,592	4,177,557
Cash and cash equivalents	49,895	108,409
Restricted cash	50,151	49,526
Accounts receivable	7,750	6,898
Deferred rent receivable	106,851	103,336
Deferred financing and leasing costs, net of accumulated amortization (2011, $120,290; 2010, $115,118)	131,047	134,419
Investments in and advances to unconsolidated joint ventures	175,472	171,916
Assets held for sale	41,533	239,113
Prepaid expenses and other assets	113,080	73,625
Total assets	4,846,371	5,064,799
LIABILITIES
Mortgage loans	293,702	320,679
Unsecured notes	1,792,643	2,039,143
Credit facility	33,000
Accounts payable	28,595	23,652
Accrued interest	24,375	29,821
Dividend and distributions payable	56,632	56,149
Other liabilities	141,959	156,803
Total liabilities	2,370,906	2,626,247
Limited partners' equity
General partner's equity - common units, 115,017,633 and 113,875,211 units outstanding as of September 30, 2010 and December 31, 2009, respectively	2,120,023	2,082,186
Noncontrolling interest - consolidated joint ventures	328	786
Total equity	2,475,465	2,438,552
Total liabilities and equity	$ 4,846,371	$ 5,064,799