Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
OPERATING ACTIVITIES
Net income	$ 107,180	$ 169,465
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	124,420	128,828
Amortization of deferred financing costs	3,581	3,948
Equity in (loss) earnings of unconsolidated joint ventures	1,397	(2,470)
Distributions from unconsolidated joint ventures	536	350
Gain on property dispositions	(5,364)	(58,083)
Noncash compensation	8,307	8,052
Changes in operating assets and liabilities:
Restricted cash	25,864	(16,792)
Accounts receivable	1,223	(2,370)
Deferred rent receivable	(5,550)	(5,361)
Prepaid expenses and other assets	(19,626)	(4,037)
Accounts payable	35,389	16,602
Accrued interest	12,030	3,236
Other liabilities	(30,356)	(2,936)
Net cash provided by operating activities	259,031	238,432
INVESTING ACTIVITIES
Investment in properties - acquisitions	(35,644)	(124,823)
Investment in properties - other	(45,221)	(51,615)
Investments in and advances to unconsolidated joint ventures	(3,529)	(11,309)
Distributions from unconsolidated joint ventures	6,967	9,257
Net proceeds from disposition of properties/land	217,430	361,154
Net proceeds from public reimbursement receivable/escrow	(682)	(18,274)
Investment in development in progress	(152,523)	(25,194)
Investment in land held for development	(32,871)	(18,475)
Investment in deferred leasing costs	17,470	16,662
Net cash (used in) provided by investing activities	(63,543)	104,059
FINANCING ACTIVITIES
Net proceeds from issuance of common shares	42,808	33,396
Redemption of preferred units	(221,000)	0
Proceeds from unsecured notes	400,000	0
Repayments of unsecured notes	(230,100)	(246,500)
Proceeds from mortgage loans	27,481	0
Repayments of mortgage loans	(28,103)	(28,407)
Proceeds from credit facility	653,350	302,900
Repayments on credit facility	(642,750)	(302,900)
Payment of deferred financing costs	(4,278)	(13)
Distribution paid on common shares	(166,564)	(163,658)
Distribution paid on units	(13,139)	(21,317)
Net cash used in financing activities	(182,295)	(426,499)
Net increase (decrease) in cash and cash equivalents	13,193	(84,008)
Increase in cash and cash equivalents related to foreign currency translation	2,672	15
Cash and cash equivalents at beginning of period	18,204	108,409
Cash and cash equivalents at end of period	34,069	24,416
Liberty Property Limited Partnership [Member]
OPERATING ACTIVITIES
Net income	107,180	169,465
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	124,420	128,828
Amortization of deferred financing costs	3,581	3,948
Equity in (loss) earnings of unconsolidated joint ventures	1,397	(2,470)
Distributions from unconsolidated joint ventures	536	350
Gain on property dispositions	(5,364)	(58,083)
Noncash compensation	8,307	8,052
Changes in operating assets and liabilities:
Restricted cash	25,864	(16,792)
Accounts receivable	1,223	(2,370)
Deferred rent receivable	(5,550)	(5,361)
Prepaid expenses and other assets	(19,626)	(4,037)
Accounts payable	35,389	16,602
Accrued interest	12,030	3,236
Other liabilities	(30,356)	(2,936)
Net cash provided by operating activities	259,031	238,432
INVESTING ACTIVITIES
Investment in properties - acquisitions	(35,644)	(124,823)
Investment in properties - other	(45,221)	(51,615)
Investments in and advances to unconsolidated joint ventures	(3,529)	(11,309)
Distributions from unconsolidated joint ventures	6,967	9,257
Net proceeds from disposition of properties/land	217,430	361,154
Net proceeds from public reimbursement receivable/escrow	(682)	(18,274)
Investment in development in progress	(152,523)	(25,194)
Investment in land held for development	(32,871)	(18,475)
Investment in deferred leasing costs	17,470	16,662
Net cash (used in) provided by investing activities	(63,543)	104,059
FINANCING ACTIVITIES
Redemption of preferred units	(221,000)	0
Proceeds from unsecured notes	400,000	0
Repayments of unsecured notes	(230,100)	(246,500)
Proceeds from mortgage loans	27,481	0
Repayments of mortgage loans	(28,103)	(28,407)
Proceeds from credit facility	653,350	302,900
Repayments on credit facility	(642,750)	(302,900)
Payment of deferred financing costs	(4,278)	(13)
Capital contributions	42,808	33,396
Distributions to partners	(179,703)	(184,975)
Net cash used in financing activities	(182,295)	(426,499)
Net increase (decrease) in cash and cash equivalents	13,193	(84,008)
Increase in cash and cash equivalents related to foreign currency translation	2,672	15
Cash and cash equivalents at beginning of period	18,204	108,409
Cash and cash equivalents at end of period	$ 34,069	$ 24,416