Segment Reporting Summary of Net Operating Income (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Straight-line rental income and expense, net	$ 24,605,000	$ 16,051,000	$ 13,743,000
Equity in earnings of unconsolidated joint ventures	21,444,000	63,310,000	47,403,000
Gain on dissolution of unconsolidated joint venture	0	0	30,697,000
Promote income	0	20,007,000	26,299,000
Interest Expense	(85,006,000)	(87,003,000)	(112,757,000)
Depreciation and amortization expense	(312,217,000)	(273,561,000)	(242,557,000)
Gain on sale of properties	204,988,000	113,669,000	162,093,000
Impairment Charges	0	(4,481,000)	(18,018,000)
Interest and other income, net	17,234,000	14,721,000	4,035,000
General and Administrative Expense	(56,218,000)	(54,944,000)	(55,389,000)
Gain on land sales	10,334,000	9,244,000	9,865,000
Other operating expenses	(3,592,000)	(2,554,000)	(3,864,000)
Loss on debt extinguishment	(388,000)	(26,104,000)	(33,934,000)
Acquisition-related activity	0	0	7,176,000
Income from continuing operations before income taxes	392,196,000	290,235,000	297,832,000
Operating Segments [Member]
Segment Reporting Information [Line Items]
Property Level Net Operating Income – Cash Basis	552,744,000	465,549,000	409,671,000
PNOI, continuing operations	563,698,000	493,593,000	467,537,000
Operating Segments [Member] | Industrial [Member]
Segment Reporting Information [Line Items]
Property Level Net Operating Income – Cash Basis	549,107,000	461,816,000	403,314,000
Operating Segments [Member] | Non-Reportable Rental Operations
Segment Reporting Information [Line Items]
Property Level Net Operating Income – Cash Basis	3,637,000	3,733,000	6,357,000
Operating Segments [Member] | Earnings from Service Operations
Segment Reporting Information [Line Items]
Earnings from Service Operations	8,642,000	4,963,000	8,343,000
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
PNOI from sold/held-for-sale properties included in continuing operations	10,954,000	28,044,000	57,866,000
Straight-line rental income and expense, net	24,604,000	13,585,000	7,897,000
Revenues related to lease buyouts	23,000	10,816,000	1,725,000
Amortization of lease concessions and above and below market rents	2,332,000	(1,732,000)	(2,126,000)
Intercompany rents and other adjusting items	290,000	(304,000)	(2,640,000)
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Equity in earnings of unconsolidated joint ventures	21,444,000	63,310,000	47,403,000
Gain on dissolution of unconsolidated joint venture	0	0	30,697,000
Promote income	0	20,007,000	26,299,000
Interest Expense	(85,006,000)	(87,003,000)	(112,757,000)
Depreciation and amortization expense	(312,217,000)	(273,561,000)	(242,557,000)
Gain on sale of properties	204,988,000	113,669,000	162,093,000
Impairment Charges	0	(4,481,000)	(18,018,000)
Interest and other income, net	17,234,000	14,721,000	4,035,000
General and Administrative Expense	(56,218,000)	(54,944,000)	(55,389,000)
Gain on land sales	10,334,000	9,244,000	9,865,000
Other operating expenses	(3,592,000)	(2,554,000)	(3,864,000)
Loss on debt extinguishment	(388,000)	(26,104,000)	(33,934,000)
Acquisition-related activity	0	0	7,176,000
Other non-segment revenues and expenses, net	$ (3,972,000)	$ (2,990,000)	$ (3,953,000)