Segment Reporting (Summary of Net Operating Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement [Line Items]
Straight-line rental income and expense, net	$ 5,704	$ 6,288
Equity in earnings of unconsolidated joint ventures	4,715	8,287
Interest expense	(22,132)	(20,000)
Depreciation and amortization expense	(75,992)	(77,529)
Gain on sale of properties	(163)	44,886
Interest and other income, net	2,758	4,463
General and administrative expenses	(21,983)	(21,023)
Gain on land sales	750	2,949
Other operating expenses	(2,123)	(1,269)
Loss on extinguishment of debt	(13)	0
Gain on involuntary conversion	2,259	0
Non-incremental costs related to successful leases	2,156	0
Income from continuing operations before income taxes	45,153	83,853
Operating Segments [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	149,777	129,180
Property Level Net Income, Cash Basis, Continuing Operations	149,750	135,915
Operating Segments [Member] | Industrial [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	148,901	128,143
Operating Segments [Member] | All Other Segments [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	876	1,037
Operating Segments [Member] | Service Operations [Member]
Statement [Line Items]
Earnings from Service Operations	2,378	692
Segment Reconciling Items [Member]
Statement [Line Items]
PNOI from sold properties included in continuing operations	(27)	6,735
Straight-line rental income and expense, net	5,704	6,288
Revenues Related to Lease Buyouts	19	23
Amortization of lease concessions and above and below market rents	1,262	545
Intercompany rents and other adjusting items	45	15
Corporate, Non-Segment [Member]
Statement [Line Items]
Equity in earnings of unconsolidated joint ventures	4,715	8,287
Interest expense	(22,132)	(20,000)
Depreciation and amortization expense	(75,992)	(77,529)
Gain on sale of properties	(163)	44,886
Interest and other income, net	2,758	4,463
General and administrative expenses	(21,983)	(21,023)
Gain on land sales	750	2,949
Other operating expenses	(2,123)	(786)
Loss on extinguishment of debt	(13)	0
Gain on involuntary conversion	2,259	0
Non-incremental costs related to successful leases	(2,156)	0
Other non-segment revenues and expenses, net	$ 75	$ (872)