Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
OPERATING ACTIVITIES
Net income	$ 290,045	$ 366,145	$ 245,924
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	183,887	207,673	229,779
Amortization of deferred financing costs	3,750	3,974	4,395
Expensed pursuit costs	5,066	1,016	605
Impairment - real estate assets	10,632	3,879	18,244
Loss on debt extinguishment	49	27,099	0
Equity in earnings of unconsolidated joint ventures	(17,155)	(21,970)	(3,149)
Distributions from unconsolidated joint ventures	0	0	2,444
Gain on property dispositions	(114,965)	(219,270)	(100,314)
Share-based compensation	14,119	19,850	17,152
Other	824	(6,128)	(9,937)
Changes in operating assets and liabilities:
Accounts receivable	3,512	421	1,009
Deferred rent receivable	(19,605)	(16,927)	(23,167)
Prepaid expenses and other assets	(33,663)	(32,442)	(15,145)
Accounts payable	10,151	8,943	1,822
Accrued interest	(82)	(4,276)	1,641
Other liabilities	66	3,075	7,818
Net cash provided by operating activities	336,631	341,062	379,121
INVESTING ACTIVITIES
Investment in properties – acquisitions	(255,639)	(9,216)	(111,811)
Investment in properties – other	(56,104)	(55,406)	(77,626)
Investments in and advances to unconsolidated joint ventures	(46,567)	(70,581)	(43,676)
Distributions from unconsolidated joint ventures	21,042	63,048	33,195
Net proceeds from disposition of properties/land	379,139	1,192,918	530,440
Investment in development in progress	(260,447)	(342,489)	(210,677)
Investment in land held for development	(105,564)	(107,400)	(150,523)
Payment of deferred leasing costs	(37,678)	(32,682)	(48,672)
Increase in escrows	(108,420)	(25,254)	(8,216)
Other	4,586	1,989	(2,094)
Net cash (used in) provided by investing activities	(465,652)	614,927	(89,660)
FINANCING ACTIVITIES
Net proceeds from issuance of common shares	8,808	13,029	38,797
Share repurchases, including shares related to tax withholdings	(5,107)	(46,268)	(76,035)
Proceeds from unsecured notes	0	396,648	398,576
Repayments of unsecured notes including prepayment premium	0	(723,368)	(316,000)
Repayments of mortgage loans	(7,795)	(29,538)	(175,364)
Proceeds from credit facility	835,036	591,300	1,122,700
Repayments on credit facility	(476,097)	(850,300)	(1,030,700)
Payment of deferred financing costs	(5,190)	(3,550)	(3,656)
Distribution paid on common shares	(246,589)	(279,248)	(282,582)
Distribution paid on units/noncontrolling interests	(6,835)	(8,212)	(7,596)
Net cash provided by (used in) financing activities	96,231	(939,507)	(331,860)
Net (decrease) increase in cash, cash equivalents and restricted cash	(32,790)	16,482	(42,399)
Increase (decrease) in cash, cash equivalents and restricted cash related to foreign currency translation	2,450	(4,828)	(2,901)
Cash, cash equivalents and restricted cash	25,685	56,025	44,371
Liberty Property Limited Partnership [Member]
OPERATING ACTIVITIES
Net income	290,045	366,145	245,924
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	183,887	207,673	229,779
Amortization of deferred financing costs	3,750	3,974	4,395
Expensed pursuit costs	5,066	1,016	605
Impairment - real estate assets	10,632	3,879	18,244
Loss on debt extinguishment	49	27,099	0
Equity in earnings of unconsolidated joint ventures	(17,155)	(21,970)	(3,149)
Distributions from unconsolidated joint ventures	0	0	2,444
Gain on property dispositions	(114,965)	(219,270)	(100,314)
Share-based compensation	14,119	19,850	17,152
Other	824	(6,128)	(9,937)
Changes in operating assets and liabilities:
Accounts receivable	3,512	421	1,009
Deferred rent receivable	(19,605)	(16,927)	(23,167)
Prepaid expenses and other assets	(33,663)	(32,442)	(15,145)
Accounts payable	10,151	8,943	1,822
Accrued interest	(82)	(4,276)	1,641
Other liabilities	66	3,075	7,818
Net cash provided by operating activities	336,631	341,062	379,121
INVESTING ACTIVITIES
Investment in properties – acquisitions	(255,639)	(9,216)	(111,811)
Investment in properties – other	(56,104)	(55,406)	(77,626)
Investments in and advances to unconsolidated joint ventures	(46,567)	(70,581)	(43,676)
Distributions from unconsolidated joint ventures	21,042	63,048	33,195
Net proceeds from disposition of properties/land	379,139	1,192,918	530,440
Investment in development in progress	(260,447)	(342,489)	(210,677)
Investment in land held for development	(105,564)	(107,400)	(150,523)
Payment of deferred leasing costs	(37,678)	(32,682)	(48,672)
Increase in escrows	(108,420)	(25,254)	(8,216)
Other	4,586	1,989	(2,094)
Net cash (used in) provided by investing activities	(465,652)	614,927	(89,660)
FINANCING ACTIVITIES
Proceeds from unsecured notes	0	396,648	398,576
Repayments of unsecured notes including prepayment premium	0	(723,368)	(316,000)
Repayments of mortgage loans	(7,795)	(29,538)	(175,364)
Proceeds from credit facility	835,036	591,300	1,122,700
Repayments on credit facility	(476,097)	(850,300)	(1,030,700)
Payment of deferred financing costs	(5,190)	(3,550)	(3,656)
Capital contributions	8,808	13,029	38,797
Distributions to partners/noncontrolling interests	(258,531)	(333,728)	(366,213)
Net cash provided by (used in) financing activities	96,231	(939,507)	(331,860)
Net (decrease) increase in cash, cash equivalents and restricted cash	(32,790)	16,482	(42,399)
Increase (decrease) in cash, cash equivalents and restricted cash related to foreign currency translation	2,450	(4,828)	(2,901)
Cash, cash equivalents and restricted cash	$ 25,685	$ 56,025	$ 44,371