Segment Reporting (Summary of Net Operating Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Straight-line rental income and expense, net			$ 12,021	$ 10,832
Equity in earnings of unconsolidated companies	$ 1,841	$ 12,010	58,523	37,404
Gain on dissolution of unconsolidated company	0	0	0	30,697
Promote income	0	2,212	20,007	26,299
Interest expense	(20,835)	(27,283)	(65,401)	(87,255)
Depreciation and amortization expense	(67,992)	(61,820)	(197,028)	(182,489)
Gain on sale of properties	21,952	82,698	93,339	137,589
Impairment Charges	(3,622)	(3,042)	(4,481)	(15,098)
Interest and other income, net	6,404	507	9,197	3,597
General and administrative expenses	(10,075)	(12,534)	(41,165)	(42,216)
Gain on land sales	5,665	1,601	8,449	2,438
Other operating expenses	(770)	(1,424)	(2,226)	(3,496)
Loss on extinguishment of debt	(16,568)	(6,243)	(26,104)	(8,673)
Acquisition-related activity	0	(7)	0	(82)
Income from continuing operations before income taxes	42,368	108,232	235,812	257,378
Operating Segments [Member]
Property Level Net Operating Income – Cash Basis	122,775	109,627	360,585	317,606
Property Level Net Income, Cash Basis, Continuing Operations	123,385	116,973	365,062	347,891
Operating Segments [Member] | Industrial [Member]
Property Level Net Operating Income – Cash Basis	121,483	108,782	357,018	312,673
Operating Segments [Member] | All Other Segments [Member]
Property Level Net Operating Income – Cash Basis	1,292	845	3,567	4,933
Operating Segments [Member] | Service Operations [Member]
Earnings from Service Operations	1,138	2,169	4,115	8,216
Segment Reconciling Items [Member]
PNOI from sold/held-for-sale properties included in continuing operations	610	7,346	4,477	30,285
Straight-line rental income and expense, net	4,341	3,451	9,547	6,371
Revenues Related to Lease Buyouts	491	1,491	10,348	1,725
Amortization of lease concessions and above and below market rents	(1,274)	(672)	(2,718)	(2,285)
Intercompany rents and other adjusting items	(108)	(463)	(478)	(1,540)
Corporate, Non-Segment [Member]
Equity in earnings of unconsolidated companies	1,841	12,010	58,523	37,404
Gain on dissolution of unconsolidated company	0	0	0	30,697
Promote income	0	2,212	20,007	26,299
Interest expense	(20,835)	(27,283)	(65,401)	(87,255)
Depreciation and amortization expense	(67,992)	(61,820)	(197,028)	(182,489)
Gain on sale of properties	21,952	82,698	93,339	137,589
Impairment Charges	(3,622)	(3,042)	(4,481)	(15,098)
Interest and other income, net	6,404	507	9,197	3,597
General and administrative expenses	(10,075)	(12,534)	(41,165)	(42,216)
Gain on land sales	5,665	1,601	8,449	2,438
Other operating expenses	(770)	(1,424)	(2,226)	(3,496)
Loss on extinguishment of debt	(16,568)	(6,243)	(26,104)	(8,673)
Acquisition-related activity	0	(7)	0	(82)
Other non-segment revenues and expenses, net	$ (1,605)	$ (1,392)	$ (3,174)	$ (1,715)