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, 2013	Mar. 31, 2012	Dec. 31, 2012
Income Per Common Unit [Line Items]
Income from continuing operations	$ 29,925	$ 31,872
Weighted Average Number of Shares Outstanding, Basic	118,688,000	115,972,000
Income from Continuing Operations, Per Basic Share	$ 0.25	$ 0.28
Dilutive units for long-term compensation plans	844,000	771,000
Weighted Average Number of Shares Outstanding, Diluted	119,532,000	116,743,000
Income from Continuing Operations, Per Diluted Share	$ 0.25	$ 0.28
Income from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	42,593	5,387
Income from Discontinued Operations, Net of Tax, Per Basic Share	$ 0.35	$ 0.04
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share	$ 0.35	$ 0.04
Net Income (Loss) Available to Common Stockholders, Basic	71,239	37,089
Earnings Per Share, Basic	$ 0.60	$ 0.32
Earnings Per Share, Diluted	$ 0.60	$ 0.32
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	992,000	1,384,000
Stock Issued During Period, Shares, Stock Options Exercised	357,000		841,000
Liberty Property Limited Partnership [Member]
Income Per Common Unit [Line Items]
Income from continuing operations	32,063	34,215
Less: Preferred unit distributions	(1,211)	(5,035)
Preferred Stock Redemption Premium	0
Preferred Stock Redemption Discount	0	3,729
Income from Continuing Operations available to Common Unitholders	30,852	32,909
Weighted Average Number of Shares Outstanding, Basic	122,402,000	119,781,000
Income from Continuing Operations, Per Basic Share	$ 0.25	$ 0.28
Dilutive units for long-term compensation plans	844,000	771,000
Weighted Average Number of Shares Outstanding, Diluted	123,246,000	120,552,000
Income from Continuing Operations, Per Diluted Share	$ 0.25	$ 0.28
Income from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	42,593	5,387
Income from Discontinued Operations, Net of Tax, Per Basic Share	$ 0.35	$ 0.04
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share	$ 0.35	$ 0.04
Net Income (Loss) Available to Common Stockholders, Basic	$ 73,445	$ 38,296
Earnings Per Share, Basic	$ 0.60	$ 0.32
Earnings Per Share, Diluted	$ 0.60	$ 0.32
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	992,000	1,384,000
Stock Issued During Period, Shares, Stock Options Exercised	357,000		841,000