Consolidated Balance Sheets (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
ASSETS
Land and land improvements	$ 857,917	$ 831,740
Building and improvements	4,223,817	4,120,456
Less accumulated depreciation	(1,097,115)	(999,263)
Operating real estate	3,984,619	3,952,933
Development in progress	41,907	0
Land held for development	208,431	209,253
Net real estate	4,234,957	4,162,186
Cash and cash equivalents	24,416	108,409
Restricted cash	66,350	49,526
Accounts receivable	9,243	6,898
Deferred rent receivable	105,406	102,924
Deferred financing and leasing costs, net of accumulated amortization (2011, $125,626; 2010, $115,124)	128,884	134,236
Investments in and advances to unconsolidated joint ventures	176,101	171,916
Assets held for sale	15,529	255,079
Prepaid expenses and other assets	94,742	73,625
Total assets	4,855,628	5,064,799
LIABILITIES
Mortgage loans	292,272	320,679
Unsecured notes	1,792,643	2,039,143
Credit facility	0	0
Accounts payable	40,257	23,652
Accrued interest	33,057	29,821
Dividend and distributions payable	56,763	56,149
Other liabilities	176,825	156,803
Total liabilities	2,391,817	2,626,247
EQUITY
Common shares of beneficial interest, $.001 par value, 183,987,000 shares authorized; 116,955,528 (includes 1,249,909 in treasury) and 115,530,608 (includes 1,249,909 in treasury) shares issued and outstanding as of September 30, 2011 and December 31, 2010, respectively	117	116
Additional paid-in capital	2,603,700	2,560,193
Accumulated other comprehensive loss	(219)	(155)
Distributions in excess of net income	(441,142)	(426,017)
Common shares in treasury, at cost, 1,249,909 shares as of September 30, 2011 and December 31, 2010	(51,951)	(51,951)
Total Liberty Property Trust shareholders' equity	2,110,505	2,082,186
Noncontrolling interest - operating partnership
Noncontrolling interest - consolidated joint ventures	275	786
Total equity	2,463,811	2,438,552
Total liabilities and equity	4,855,628	5,064,799
Liberty Property Limited Partnership [Member]
ASSETS
Land and land improvements	857,917	831,740
Building and improvements	4,223,817	4,120,456
Less accumulated depreciation	(1,097,115)	(999,263)
Operating real estate	3,984,619	3,952,933
Development in progress	41,907	0
Land held for development	208,431	209,253
Net real estate	4,234,957	4,162,186
Cash and cash equivalents	24,416	108,409
Restricted cash	66,350	49,526
Accounts receivable	9,243	6,898
Deferred rent receivable	105,406	102,924
Deferred financing and leasing costs, net of accumulated amortization (2011, $125,626; 2010, $115,124)	128,884	134,236
Investments in and advances to unconsolidated joint ventures	176,101	171,916
Assets held for sale	15,529	255,079
Prepaid expenses and other assets	94,742	73,625
Total assets	4,855,628	5,064,799
LIABILITIES
Mortgage loans	292,272	320,679
Unsecured notes	1,792,643	2,039,143
Credit facility	0	0
Accounts payable	40,257	23,652
Accrued interest	33,057	29,821
Dividend and distributions payable	56,763	56,149
Other liabilities	176,825	156,803
Total liabilities	2,391,817	2,626,247
EQUITY
General Partners' Capital Account	2,110,505	2,082,186
Noncontrolling interest - operating partnership
Noncontrolling interest - consolidated joint ventures	275	786
Total equity	2,463,811	2,438,552
Total liabilities and equity	4,855,628	5,064,799
Liberty Property Limited Partnership [Member] | Limited Partner's Common Units [Member]
EQUITY
Limited partners' equity	65,072	67,621
Liberty Property Limited Partnership [Member] | Limited Partner's Preferred Units [Member]
EQUITY
Limited partners' equity	287,959	287,959
Limited Partner's Common Units [Member]
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnerships	65,072	67,621
Limited Partner's Preferred Units [Member]
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnerships	$ 287,959	$ 287,959