Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
OPERATING ACTIVITIES
Net income	$ 210,710	$ 153,375	$ 78,992
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	171,714	174,013	172,575
Amortization of deferred financing costs	5,190	6,339	5,101
Impairment charges - investment in unconsolidated joint ventures and other	0	378	98,252
Debt extinguishment gain	0	0	(1,547)
Equity in earnings of unconsolidated joint ventures	(3,496)	(2,296)	(2,161)
Distributions from unconsolidated joint ventures	551	657	663
Gain on property dispositions	(65,607)	(11,473)	(19,546)
Noncash compensation	10,555	11,595	12,905
Changes in operating assets and liabilities:
Restricted cash	(14,114)	(7,294)	(1,189)
Accounts receivable	(1,320)	(850)	4,191
Deferred rent receivable	(6,566)	(13,581)	(13,414)
Prepaid expenses and other assets	6,027	(7,597)	3,699
Accounts payable	(229)	(7,399)	(1,099)
Accrued interest	(5,674)	(1,430)	(5,223)
Other liabilities	9,983	(2,173)	(24,998)
Net cash provided by operating activities	317,724	292,264	307,201
INVESTING ACTIVITIES
Investment in properties - acquisitions	(233,568)	(43,505)	0
Investment in properties - other	(75,834)	(75,857)	(58,871)
Investments in and advances to unconsolidated joint ventures	(11,195)	(1,870)	(5,132)
Distributions from unconsolidated joint ventures	11,364	6,776	20,721
Net proceeds from disposition of properties/land	390,754	35,934	190,534
Net (advances on) proceeds from public reimbursement receivable/escrow	(10,237)	18,917	(23,238)
Investment in development in progress	(48,628)	(7,481)	(79,586)
Investment in land held for development	(52,868)	(6,086)	(29,391)
Investment in deferred leasing costs	(26,011)	(30,289)	(29,369)
Net cash used in investing activities	(56,223)	(103,461)	(14,332)
FINANCING ACTIVITIES
Net proceeds from issuance of Common Shares	44,552	37,434	293,814
Redemption of preferred units	(9,060)	0	0
Proceeds from unsecured notes	0	366,000	0
Repayments of unsecured notes	(246,500)	(169,739)	(287,179)
Proceeds from mortgage loans	0	743	330,250
Repayments of mortgage loans	(29,860)	(156,890)	(54,864)
Proceeds from credit facility	650,500	338,500	199,150
Repayments on credit facility	(511,100)	(478,500)	(319,150)
Increase in deferred financing costs	(3,023)	(9,697)	(5,550)
Distribution paid on Common Shares	(218,613)	(215,083)	(201,984)
Distribution paid on units	(28,409)	(28,610)	(28,520)
Net cash used in financing activities	(351,513)	(315,842)	(74,033)
Net (decrease) increase in cash and cash equivalents	(90,012)	(127,039)	218,836
(Decrease) increase in cash and cash equivalents related to foreign currency translation	(193)	(1,998)	2,816
Cash and cash equivalents at beginning of period	108,409	237,446	15,794
Cash and cash equivalents at end of period	18,204	108,409	237,446
Liberty Property Limited Partnership [Member]
OPERATING ACTIVITIES
Net income	210,710	153,375	78,992
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	171,714	174,013	172,575
Amortization of deferred financing costs	5,190	6,339	5,101
Impairment charges - investment in unconsolidated joint ventures and other	0	378	98,252
Debt extinguishment gain	0	0	(1,547)
Equity in earnings of unconsolidated joint ventures	(3,496)	(2,296)	(2,161)
Distributions from unconsolidated joint ventures	551	657	663
Gain on property dispositions	(65,607)	(11,473)	(19,546)
Noncash compensation	10,555	11,595	12,905
Changes in operating assets and liabilities:
Restricted cash	(14,114)	(7,294)	(1,189)
Accounts receivable	(1,320)	(850)	4,191
Deferred rent receivable	(6,566)	(13,581)	(13,414)
Prepaid expenses and other assets	6,027	(7,597)	3,699
Accounts payable	(229)	(7,399)	(1,099)
Accrued interest	(5,674)	(1,430)	(5,223)
Other liabilities	9,983	(2,173)	(24,998)
Net cash provided by operating activities	317,724	292,264	307,201
INVESTING ACTIVITIES
Investment in properties - acquisitions	(233,568)	(43,505)	0
Investment in properties - other	(75,834)	(75,857)	(58,871)
Investments in and advances to unconsolidated joint ventures	(11,195)	(1,870)	(5,132)
Distributions from unconsolidated joint ventures	11,364	6,776	20,721
Net proceeds from disposition of properties/land	390,754	35,934	190,534
Net (advances on) proceeds from public reimbursement receivable/escrow	(10,237)	18,917	(23,238)
Investment in development in progress	(48,628)	(7,481)	(79,586)
Investment in land held for development	(52,868)	(6,086)	(29,391)
Investment in deferred leasing costs	(26,011)	(30,289)	(29,369)
Net cash used in investing activities	(56,223)	(103,461)	(14,332)
FINANCING ACTIVITIES
Redemption of preferred units	(9,060)	0	0
Proceeds from unsecured notes	0	366,000	0
Repayments of unsecured notes	(246,500)	(169,739)	(287,179)
Proceeds from mortgage loans	0	743	330,250
Repayments of mortgage loans	(29,860)	(156,890)	(54,864)
Proceeds from credit facility	650,500	338,500	199,150
Repayments on credit facility	(511,100)	(478,500)	(319,150)
Increase in deferred financing costs	(3,023)	(9,697)	(5,550)
Capital contributions	44,552	37,434	293,814
Distributions to partners	(247,022)	(243,693)	(230,504)
Net cash used in financing activities	(351,513)	(315,842)	(74,033)
Net (decrease) increase in cash and cash equivalents			218,836
(Decrease) increase in cash and cash equivalents related to foreign currency translation	(193)	(1,998)	2,816
Cash and cash equivalents at beginning of period	108,409	237,446	15,794
Cash and cash equivalents at end of period	$ 18,204	$ 108,409	$ 237,446