Shareholders' Equity - Common Shares (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Class of Stock [Line Items]
Authorized but Unissued Preferred Shares	6,273,000
Common Stock, Dividends, Per Share, Cash Paid	$ 1.900	$ 1.900	$ 1.900
Net proceeds from the issuance of common shares	$ 44,548,000	$ 37,416,000	$ 293,858,000
Liberty Property Limited Partnership [Member]
Class of Stock [Line Items]
Common Stock, Dividends, Per Share, Cash Paid	$ 1.900	$ 1.900	$ 1.900
Common Shares and Common Units [Member]
Class of Stock [Line Items]
Dividends, Common Stock, Cash	226,000,000	222,600,000	209,600,000
Common Stock [Member]
Class of Stock [Line Items]
Common Stock, Dividends, Per Share, Cash Paid	$ 1.9000	$ 1.9000	$ 1.9000
Treasury Stock [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount	100,000,000
Dividend Reinvestment Plan [Member] | Common Stock [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, Dividend Reinvestment Plan	1,181,776	915,363	304,587
Continuous Equity Offering [Member] | Common Stock [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues			12,800,000
Net proceeds from the issuance of common shares			$ 283,200,000
Stock Issued During Period, Shares, Other	0	0
Continuous Equity Offering [Member] | Common Stock [Member] | Liberty Property Limited Partnership [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, Other	0	0
Share Repurchase Plan [Member] | Treasury Stock [Member]
Class of Stock [Line Items]
Treasury Shares Repurchased	0	0	0
Ordinary Dividend [Member] | Common Stock [Member]
Class of Stock [Line Items]
Common Stock, Dividends, Per Share, Cash Paid	$ 1.4300	$ 1.4812	$ 1.6772
Qualified Dividend [Member] | Common Stock [Member]
Class of Stock [Line Items]
Common Stock, Dividends, Per Share, Cash Paid	$ 0.0000	$ 0.0000	$ 0.0000
Capital Gain - 15% [Member] | Common Stock [Member]
Class of Stock [Line Items]
Common Stock, Dividends, Per Share, Cash Paid	$ 0.1708	$ 0.0000	$ 0.0976
IRC Sec 1250 Unrecaptured Gain - 25% [Member] | Common Stock [Member]
Class of Stock [Line Items]
Common Stock, Dividends, Per Share, Cash Paid	$ 0.2992	$ 0.0128	$ 0.1252
Return of Capital [Member] | Common Stock [Member]
Class of Stock [Line Items]
Common Stock, Dividends, Per Share, Cash Paid	$ 0.0000	$ 0.4060	$ 0.0000