Segment Reporting (Summary of Net Operating Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement [Line Items]
Straight-line rental income and expense, net			$ 10,466	$ 10,931
Equity in earnings of unconsolidated joint ventures	$ 4,143	$ 1,682	8,858	9,969
Interest expense	(23,510)	(20,675)	(45,642)	(40,675)
Depreciation and amortization expense	(83,004)	(75,832)	(158,996)	(153,361)
Gain on sale of properties	30,592	149,962	30,429	194,848
Interest and other income, net	2,534	4,727	5,292	9,190
General and administrative expenses	(13,420)	(13,459)	(35,403)	(34,482)
Gain on land sales	1,950	357	2,700	3,306
Other operating expenses	(1,518)	(1,529)	(3,641)	(2,798)
Loss on extinguishment of debt	0	(151)	(13)	(151)
Gain on involuntary conversion	0	0	2,259	0
Non-incremental costs related to successful leases	3,447	0	5,603	0
Income from continuing operations before income taxes	78,185	192,814	123,338	276,667
Operating Segments [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	155,796	137,677	305,580	267,344
Property Level Net Income, Cash Basis, Continuing Operations	156,183	140,794	305,935	277,192
Operating Segments [Member] | Industrial [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	154,934	136,316	303,840	264,463
Operating Segments [Member] | All Other Segments [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	862	1,361	1,740	2,881
Operating Segments [Member] | Service Operations [Member]
Statement [Line Items]
Earnings from Service Operations	730	3,212	3,108	3,904
Segment Reconciling Items [Member]
Statement [Line Items]
PNOI from sold properties included in continuing operations	387	3,117	355	9,848
Straight-line rental income and expense, net	4,762	4,642	10,466	10,931
Revenues Related to Lease Buyouts	0	0	19	23
Amortization of lease concessions and above and below market rents	1,542	461	2,804	1,006
Intercompany rents and other adjusting items	60	(20)	103	(6)
Corporate, Non-Segment [Member]
Statement [Line Items]
Equity in earnings of unconsolidated joint ventures	4,143	1,682	8,858	9,969
Interest expense	(23,510)	(20,675)	(45,642)	(40,675)
Depreciation and amortization expense	(83,004)	(75,832)	(158,996)	(153,361)
Gain on sale of properties	30,592	149,962	30,429	194,848
Interest and other income, net	2,534	4,727	5,292	9,190
General and administrative expenses	(13,420)	(13,459)	(35,403)	(34,482)
Gain on land sales	1,950	357	2,700	3,306
Other operating expenses	(1,518)	(1,529)	(3,641)	(2,798)
Loss on extinguishment of debt	0	(151)	(13)	(151)
Gain on involuntary conversion	0	0	2,259	0
Non-incremental costs related to successful leases	(3,447)	0	(5,603)	0
Other non-segment revenues and expenses, net	$ 588	$ (1,357)	$ 663	$ (2,229)