Income per Common Unit of the Operating Partnership (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Per Common Unit [Line Items]
Income from continuing operations net of noncontrolling interest																	$ 115,469	$ 105,172	$ 9,623
Weighted Average Number of Shares Outstanding, Basic																	114,755,000	112,924,000	107,550,000
Income (Loss) from Continuing Operations, Per Basic Share																	$ 1.00	$ 0.93	$ 0.09
Dilutive units for long-term compensation plans																	748,000	682,000	452,000
Weighted Average Number of Shares Outstanding, Diluted																	115,503,000	113,606,000	108,002,000
Income (Loss) from Continuing Operations, Per Diluted Share																	$ 1.00	$ 0.92	$ 0.09
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	6,929		5,824		53,907		4,179		4,471		5,106		6,438		7,358		70,839	23,373	48,466
Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share																	$ 0.60	$ 0.20	$ 0.43
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share																	$ 0.59	$ 0.20	$ 0.43
Net Income (Loss) Available to Common Stockholders, Basic																	183,999	127,762	56,376
Earnings Per Share, Basic	$ 0.30	[1]	$ 0.31	[1]	$ 0.74	[1]	$ 0.25	[1]	$ 0.27	[1]	$ 0.31	[1]	$ 0.30	[1]	$ 0.26	[1]	$ 1.60	$ 1.13	$ 0.52
Earnings Per Share, Diluted	$ 0.30	[1]	$ 0.31	[1]	$ 0.74	[1]	$ 0.25	[1]	$ 0.26	[1]	$ 0.30	[1]	$ 0.29	[1]	$ 0.26	[1]	$ 1.59	$ 1.12	$ 0.52
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount																	1,685,000	1,433,000	2,661,000
Stock Issued During Period, Shares, Stock Options Exercised																	256,000	315,000	187,000
Common Units Exchanged																	119,987	82,621	63,613
Liberty Property Limited Partnership [Member]
Income Per Common Unit [Line Items]
Income from continuing operations net of noncontrolling interest																	140,382	129,837	31,035
Less: Preferred unit distributions																	(21,069)	(21,012)	(21,012)
Income from Continuing Operations available to Common Unitholders																	119,313	108,825	10,023
Weighted Average Number of Shares Outstanding, Basic																	118,624,000	116,871,000	111,568,000
Income (Loss) from Continuing Operations, Per Basic Share																	$ 1.00	$ 0.93	$ 0.09
Dilutive units for long-term compensation plans																	748,000	682,000	452,000
Weighted Average Number of Shares Outstanding, Diluted																	119,372,000	117,553,000	112,020,000
Income (Loss) from Continuing Operations, Per Diluted Share																	$ 1.00	$ 0.92	$ 0.09
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest																	70,839	23,373	48,466
Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share																	$ 0.60	$ 0.20	$ 0.43
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share																	$ 0.59	$ 0.20	$ 0.43
Net Income (Loss) Available to Common Stockholders, Basic																	$ 190,152	$ 132,198	$ 58,489
Earnings Per Share, Basic																	$ 1.60	$ 1.13	$ 0.52
Earnings Per Share, Diluted																	$ 1.59	$ 1.12	$ 0.52
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount																	1,685,000	1,433,000	2,661,000
Stock Issued During Period, Shares, Stock Options Exercised																	256,000	315,000	187,000
Common Units Exchanged																	119,987	82,621	63,613

[1] The sum of quarterly financial data may vary from the annual data due to rounding.