Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
ASSETS
Land and land improvements	$ 900,963	$ 899,801
Building and improvements	4,374,877	4,341,125
Less accumulated depreciation	(1,178,309)	(1,164,756)
Operating real estate	4,097,531	4,076,170
Development in progress	209,690	248,602
Land held for development	246,572	258,324
Net real estate	4,553,793	4,583,096
Cash and cash equivalents	54,434	38,356
Restricted cash	28,212	33,147
Accounts receivable	8,355	8,988
Deferred rent receivable	110,078	108,576
Deferred financing and leasing costs, net of accumulated amortization (2013, $134,299; 2012, $132,261)	134,316	137,359
Investments in and advances to unconsolidated joint ventures	175,285	169,021
Assets held for sale	7,829	7,880
Prepaid expenses and other assets	74,371	87,756
Total assets	5,146,673	5,174,179
LIABILITIES
Mortgage loans	304,867	302,855
Unsecured notes	2,258,946	2,258,751
Credit facility	0	92,000
Accounts payable	32,152	31,058
Accrued interest	39,031	20,164
Dividend and distributions payable	59,813	58,038
Other liabilities	167,337	185,956
Total liabilities	2,862,146	2,948,822
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of March 31, 2013 and December 31, 2012	7,537	7,537
EQUITY
Common shares of beneficial interest, $.001 par value, 183,987,000 shares authorized; 121,181,984 (includes 1,249,909 in treasury) and 119,720,776 (includes 1,249,909 in treasury) shares issued and outstanding as of March 31, 2013 and December 31, 2012, respectively	121	119
Additional paid-in capital	2,737,071	2,687,701
Accumulated other comprehensive loss	(1,805)	2,900
Distributions in excess of net income	(533,471)	(547,757)
Common shares in treasury, at cost, 1,249,909 shares as of March 31, 2013 and December 31, 2012	(51,951)	(51,951)
Total Liberty Property Trust shareholders' equity	2,149,965	2,091,012
Noncontrolling interest - operating partnership
Noncontrolling interest - consolidated joint ventures	3,321	3,321
Total equity	2,276,990	2,217,820
Total liabilities, noncontrolling interest - operating partnership and equity	5,146,673	5,174,179
3,713,851 common units outstanding as of March 31, 2013 and December 31, 2012, respectively
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnerships	60,440	60,223
1,290,000 preferred units outstanding as of March 31, 2013 and December 31, 2012, respectively
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnerships	63,264	63,264
Liberty Property Limited Partnership [Member]
ASSETS
Land and land improvements	900,963	899,801
Building and improvements	4,374,877	4,341,125
Less accumulated depreciation	(1,178,309)	(1,164,756)
Operating real estate	4,097,531	4,076,170
Development in progress	209,690	248,602
Land held for development	246,572	258,324
Net real estate	4,553,793	4,583,096
Cash and cash equivalents	54,434	38,356
Restricted cash	28,212	33,147
Accounts receivable	8,355	8,988
Deferred rent receivable	110,078	108,576
Deferred financing and leasing costs, net of accumulated amortization (2013, $134,299; 2012, $132,261)	134,316	137,359
Investments in and advances to unconsolidated joint ventures	175,285	169,021
Assets held for sale	7,829	7,880
Prepaid expenses and other assets	74,371	87,756
Total assets	5,146,673	5,174,179
LIABILITIES
Mortgage loans	304,867	302,855
Unsecured notes	2,258,946	2,258,751
Credit facility	0	92,000
Accounts payable	32,152	31,058
Accrued interest	39,031	20,164
Dividend and distributions payable	59,813	58,038
Other liabilities	167,337	185,956
Total liabilities	2,862,146	2,948,822
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of March 31, 2013 and December 31, 2012	7,537	7,537
EQUITY
General partner’s equity - 119,932,075 (net of 1,249,909 treasury units) and 118,470,867 (net of 1,249,909 treasury units) common units outstanding as of March 31, 2013 and December 31, 2012, respectively	2,149,965	2,091,012
Noncontrolling interest - operating partnership
Noncontrolling interest - consolidated joint ventures	3,321	3,321
Total equity	2,276,990	2,217,820
Total liabilities, noncontrolling interest - operating partnership and equity	5,146,673	5,174,179
Liberty Property Limited Partnership [Member] | 3,713,851 common units outstanding as of March 31, 2013 and December 31, 2012, respectively
EQUITY
Limited partners' equity	60,440	60,223
Liberty Property Limited Partnership [Member] | 1,290,000 preferred units outstanding as of March 31, 2013 and December 31, 2012, respectively
EQUITY
Limited partners' equity	$ 63,264	$ 63,264