Income per Common Unit of the Operating Partnership (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Income Per Common Unit [Line Items]
Income from continuing operations net of noncontrolling interest	$ 31,110	$ 32,717	$ 63,551	$ 57,513
Preferred Stock Redemption Premium	(40)
Preferred Stock Redemption Discount			3,689
Weighted Average Number of Shares Outstanding, Basic	116,683,000	114,623,000	116,359,000	114,285,000
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.26	$ 0.28	$ 0.54	$ 0.51
Dilutive units for long-term compensation plans	876,000	783,000	806,000	802,000
Weighted Average Number of Shares Outstanding, Diluted	117,559,000	115,406,000	117,165,000	115,087,000
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.26	$ 0.28	$ 0.54	$ 0.50
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	3,097	54,028	7,895	58,292
Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share	$ 0.03	$ 0.46	$ 0.07	$ 0.49
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share	$ 0.03	$ 0.46	$ 0.07	$ 0.49
Net Income (Loss) Available to Common Stockholders, Basic	34,111	84,978	71,200	113,887
Earnings Per Share, Basic	$ 0.29	$ 0.74	$ 0.61	$ 1.00
Earnings Per Share, Diluted	$ 0.29	$ 0.74	$ 0.61	$ 0.99
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	953,000	965,000	925,000	1,119,000
Stock Issued During Period, Shares, Stock Options Exercised	162,000		511,000		256,000
Liberty Property Limited Partnership [Member]
Income Per Common Unit [Line Items]
Income from continuing operations net of noncontrolling interest	34,583	39,070	69,387	69,950
Less: Preferred unit distributions	(2,444)	(5,253)	(7,479)	(10,506)
Preferred Stock Redemption Premium	(40)
Preferred Stock Redemption Discount		0	3,689	0
Income from Continuing Operations available to Common Unitholders	32,099	33,817	65,597	59,444
Weighted Average Number of Shares Outstanding, Basic	120,450,000	118,549,000	120,147,000	118,212,000
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.26	$ 0.28	$ 0.54	$ 0.51
Dilutive units for long-term compensation plans	876,000	783,000	806,000	802,000
Weighted Average Number of Shares Outstanding, Diluted	121,326,000	119,332,000	120,953,000	119,014,000
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.26	$ 0.28	$ 0.54	$ 0.50
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	3,097	54,028	7,895	58,292
Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share	$ 0.03	$ 0.46	$ 0.07	$ 0.49
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share	$ 0.03	$ 0.46	$ 0.07	$ 0.49
Net Income (Loss) Available to Common Stockholders, Basic	$ 35,196	$ 87,845	$ 73,492	$ 117,736
Earnings Per Share, Basic	$ 0.29	$ 0.74	$ 0.61	$ 1.00
Earnings Per Share, Diluted	$ 0.29	$ 0.74		$ 0.99
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	953,000	965,000	925,000	1,119,000
Stock Issued During Period, Shares, Stock Options Exercised	162,000		511,000		256,000