Segment Reporting (Summary of Net Operating Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Straight line rental income and expenses, net			$ 7,722	$ 5,768
Income from Equity Method Investments	$ 51,933	$ 3,534	56,682	25,394
Gain on dissolution of unconsolidated company	0	30,697	0	30,697
Promote income	20,007	24,087	20,007	24,087
Interest expense	(21,680)	(29,511)	(44,566)	(59,644)
Depreciation and amortization on continuing operations	(67,013)	(61,136)	(129,036)	(120,669)
Gain on sale of properties	34,341	39,314	71,387	54,891
Impairment Charges	0	(5,651)	(859)	(12,056)
Interest and other income, net	2,260	567	2,792	3,090
General and administrative expenses	(11,858)	(11,584)	(31,090)	(29,682)
Gain on land sales	1,279	707	2,784	837
Other operating expenses	(718)	(836)	(1,457)	(2,072)
Gain on Extinguishment of Debt	(9,561)	(2,430)	(9,536)	(2,430)
Acquisition-related activity	0	(72)	0	(75)
Income from continuing operations before income taxes	124,620	107,496	193,442	149,475
Operating Segments [Member]
Property Level Net Operating Income – Cash Basis	122,096	105,817	239,771	209,078
Property Level Net Income, Cash Basis, Continuing Operations	122,468	115,629	241,727	230,444
Operating Segments [Member] | Industrial [Member]
Property Level Net Operating Income – Cash Basis	120,346	103,289	235,535	203,892
Operating Segments [Member] | All Other Segments [Member]
Property Level Net Operating Income – Cash Basis	1,750	2,528	4,236	5,186
Operating Segments [Member] | Service Operations [Member]
Service Operations Net Income (loss)	1,202	3,816	2,977	6,047
Segment Reconciling Items [Member]
Sold Properties Included in Continuing Operations Net Operating Income	372	9,812	1,956	21,366
Straight line rental income and expenses, net	3,628	1,323	5,205	2,920
Revenues Related to Lease Buyouts	72	69	9,857	234
Amortization of lease incentives and market rents	(566)	(695)	(1,450)	(1,612)
Intercompany rents and other adjusting items	(188)	(412)	(413)	(603)
Corporate, Non-Segment [Member]
Income from Equity Method Investments	51,933	3,534	56,682	25,394
Gain on dissolution of unconsolidated company	0	30,697	0	30,697
Promote income	20,007	24,087	20,007	24,087
Interest expense	(21,680)	(29,511)	(44,566)	(59,644)
Depreciation and amortization on continuing operations	(67,013)	(61,136)	(129,036)	(120,669)
Gain on sale of properties	34,341	39,314	71,387	54,891
Impairment Charges	0	(5,651)	(859)	(12,056)
Interest and other income, net	2,260	567	2,792	3,090
General and administrative expenses	(11,858)	(11,584)	(31,090)	(29,682)
Gain on land sales	1,279	707	2,784	837
Other operating expenses	(718)	(836)	(1,457)	(2,072)
Gain on Extinguishment of Debt	(9,561)	(2,430)	(9,536)	(2,430)
Acquisition-related activity	0	(72)	0	(75)
Other non-segment income	$ (986)	$ 80	$ (1,569)	$ (323)