Segment Reporting (Summary of Net Operating Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement [Line Items]
Straight-line rental income and expense, net	$ 6,288	$ 2,928
Equity in earnings of unconsolidated joint ventures	8,287	4,749
Interest expense	(20,000)	(24,162)
Depreciation and amortization expense	(77,529)	(62,023)
Gain on sale of properties	44,886	37,046
Impairment Charges	0	(859)
Interest and other income, net	4,463	533
General and administrative expenses	(21,023)	(19,232)
Gain on land sales	2,949	1,505
Other operating expenses	(786)	(738)
Gain on extinguishment of debt	0	25
Income from continuing operations before income taxes	83,853	67,547
Operating Segments [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	134,309	115,607
Property Level Net Income, Cash Basis, Continuing Operations	135,915	118,512
Operating Segments [Member] | Industrial [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	133,388	114,680
Operating Segments [Member] | All Other Segments [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	921	927
Operating Segments [Member] | Service Operations [Member]
Statement [Line Items]
Earnings from Service Operations	692	1,775
Segment Reconciling Items [Member]
Statement [Line Items]
PNOI from sold properties included in continuing operations	1,606	2,905
Straight-line rental income and expense, net	6,289	1,577
Revenues Related to Lease Buyouts	23	9,785
Amortization of lease concessions and above and below market rents	545	(543)
Intercompany rents and other adjusting items	14	180
Corporate, Non-Segment [Member]
Statement [Line Items]
Equity in earnings of unconsolidated joint ventures	8,287	4,749
Interest expense	(20,000)	(24,162)
Depreciation and amortization expense	(77,529)	(62,023)
Gain on sale of properties	44,886	37,046
Impairment Charges	0	(859)
Interest and other income, net	4,463	533
General and administrative expenses	(21,023)	(19,232)
Gain on land sales	2,949	1,505
Other operating expenses	(786)	(738)
Gain on extinguishment of debt	0	25
Other non-segment revenues and expenses, net	$ (872)	$ (583)