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, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Income Per Common Unit [Line Items]
Income from continuing operations	$ 33,362	$ 29,449	$ 62,762	$ 60,786
Preferred stock redemption premium	(1,236)		(1,236)
Weighted Average Number of Shares Outstanding, Basic	120,081,000	116,683,000	119,416,000	116,359,000
Income from Continuing Operations, Per Basic Share	$ 0.27	$ 0.25	$ 0.53	$ 0.52
Dilutive units for long-term compensation plans	830,000	876,000	813,000	806,000
Weighted Average Number of Shares Outstanding, Diluted	120,911,000	117,559,000	120,229,000	117,165,000
Income from Continuing Operations, Per Diluted Share	$ 0.27	$ 0.25	$ 0.53	$ 0.52
Income from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	6,953	4,810	50,078	10,749
Income from Discontinued Operations, Net of Tax, Per Basic Share	$ 0.06	$ 0.04	$ 0.40	$ 0.09
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share	$ 0.06	$ 0.04	$ 0.40	$ 0.09
Net Income (Loss) Available to Common Stockholders, Basic	40,109	34,111	111,348	71,200
Earnings Per Share, Basic	$ 0.33	$ 0.29	$ 0.93	$ 0.61
Earnings Per Share, Diluted	$ 0.33	$ 0.29	$ 0.93	$ 0.61
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	625,000	953,000	773,000	925,000
Stock Issued During Period, Shares, Stock Options Exercised	120,000		477,000		841,000
Liberty Property Limited Partnership [Member]
Income Per Common Unit [Line Items]
Income from continuing operations	36,290	32,870	67,821	66,533
Less: Preferred unit distributions	(672)	(2,444)	(1,883)	(7,479)
Preferred stock redemption premium	(1,236)	(40)	(1,236)
Preferred stock redemption discount				3,689
Income from Continuing Operations available to Common Unitholders	34,382	30,386	64,702	62,743
Weighted Average Number of Shares Outstanding, Basic	123,795,000	120,450,000	123,130,000	120,147,000
Income from Continuing Operations, Per Basic Share	$ 0.27	$ 0.25	$ 0.53	$ 0.52
Dilutive units for long-term compensation plans	830,000	876,000	813,000	806,000
Weighted Average Number of Shares Outstanding, Diluted	124,625,000	121,326,000	123,943,000	120,953,000
Income from Continuing Operations, Per Diluted Share	$ 0.27	$ 0.25	$ 0.53	$ 0.52
Income from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	6,953	4,810	50,078	10,749
Income from Discontinued Operations, Net of Tax, Per Basic Share	$ 0.06	$ 0.04	$ 0.40	$ 0.09
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share	$ 0.06	$ 0.04	$ 0.40	$ 0.09
Net Income (Loss) Available to Common Stockholders, Basic	$ 41,335	$ 35,196	$ 114,780	$ 73,492
Earnings Per Share, Basic	$ 0.33	$ 0.29	$ 0.93	$ 0.61
Earnings Per Share, Diluted	$ 0.33	$ 0.29	$ 0.93	$ 0.61
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	625,000	953,000	773,000	925,000
Stock Issued During Period, Shares, Stock Options Exercised	120,000		477,000		841,000