Income per Common Unit of the Operating Partnership (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Income Per Common Unit [Line Items]
Income from continuing operations net of noncontrolling interest	$ 33,301	$ 24,820
Preferred Stock Redemption Discount	3,729
Weighted Average Number of Shares Outstanding, Basic	115,972,000	114,013,000
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.29	$ 0.21
Dilutive units for long-term compensation plans	771,000	753,000
Weighted Average Number of Shares Outstanding, Diluted	116,743,000	114,766,000
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.29	$ 0.21
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	3,911	4,229
Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share	$ 0.03	$ 0.04
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share	$ 0.03	$ 0.04
Net Income (Loss) Available to Common Stockholders, Basic	37,089	28,909
Earnings Per Share, Basic	$ 0.32	$ 0.25
Earnings Per Share, Diluted	$ 0.32	$ 0.25
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,384,000	1,219,000
Stock Issued During Period, Shares, Stock Options Exercised	349,000		256,000
Liberty Property Limited Partnership [Member]
Income Per Common Unit [Line Items]
Income from continuing operations net of noncontrolling interest	35,691	30,915
Less: Preferred unit distributions	(5,035)	(5,253)
Preferred Stock Redemption Discount	3,729	0
Income from Continuing Operations available to Common Unitholders	34,385	25,662
Weighted Average Number of Shares Outstanding, Basic	119,781,000	117,942,000
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.29	$ 0.21
Dilutive units for long-term compensation plans	771,000	753,000
Weighted Average Number of Shares Outstanding, Diluted	120,552,000	118,695,000
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.29	$ 0.21
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	3,911	4,229
Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share	$ 0.03	$ 0.04
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share	$ 0.03	$ 0.04
Net Income (Loss) Available to Common Stockholders, Basic	$ 38,296	$ 29,891
Earnings Per Share, Basic	$ 0.32	$ 0.25
Earnings Per Share, Diluted	$ 0.32	$ 0.25
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,384,000	1,219,000
Stock Issued During Period, Shares, Stock Options Exercised	349,000		256,000