Segment Reporting (Summary of Net Operating Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement [Line Items]
Straight-line rental income and expense, net			$ 8,476	$ 10,466
Equity in earnings of unconsolidated joint ventures	$ 2,396	$ 4,143	4,935	8,858
Interest expense	(22,841)	(23,510)	(46,335)	(45,642)
Depreciation and amortization expense	(86,704)	(83,004)	(172,063)	(158,996)
Gain on sale of properties	0	30,592	8,937	30,429
Impairment charges	0	0	(5,626)	0
Interest and other income, net	216	2,534	1,611	5,292
General and administrative expenses	(13,606)	(13,420)	(35,369)	(35,403)
Gain on land sales	6,070	1,950	6,205	2,700
Other operating expenses	(1,546)	(1,518)	(2,658)	(3,641)
Loss on extinguishment of debt	(14,972)	0	(32,778)	(13)
Gain on involuntary conversion	1,283	0	1,283	2,259
Non-incremental costs related to successful leases	4,034	3,447	6,559	5,603
Income from continuing operations before income taxes	40,047	78,185	59,599	123,338
Operating Segments [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	162,019	150,231	320,177	293,991
Property Level Net Income, Cash Basis, Continuing Operations	162,016	156,183	320,288	305,935
Operating Segments [Member] | Industrial [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	160,966	149,369	317,305	292,251
Operating Segments [Member] | All Other Segments [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	1,053	862	2,872	1,740
Operating Segments [Member] | Service Operations [Member]
Statement [Line Items]
Earnings from Service Operations	1,731	730	2,777	3,108
Segment Reconciling Items [Member]
Statement [Line Items]
PNOI from sold properties included in continuing operations	(3)	5,952	111	11,944
Straight-line rental income and expense, net	6,774	4,762	8,476	10,466
Revenues Related to Lease Buyouts	2,033	0	2,426	19
Amortization of lease concessions and above and below market rents	1,540	1,542	4,097	2,804
Intercompany rents and other adjusting items	(703)	60	(375)	103
Corporate, Non-Segment [Member]
Statement [Line Items]
Equity in earnings of unconsolidated joint ventures	2,396	4,143	4,935	8,858
Interest expense	(22,841)	(23,510)	(46,335)	(45,642)
Depreciation and amortization expense	(86,704)	(83,004)	(172,063)	(158,996)
Gain on sale of properties	0	30,592	8,937	30,429
Interest and other income, net	216	2,534	1,611	5,292
General and administrative expenses	(13,606)	(13,420)	(35,369)	(35,403)
Gain on land sales	6,070	1,950	6,205	2,700
Other operating expenses	(1,546)	(1,518)	(2,658)	(3,641)
Loss on extinguishment of debt	(14,972)	0	(32,778)	(13)
Gain on involuntary conversion	1,283	0	1,283	2,259
Non-incremental costs related to successful leases	(4,034)	(3,447)	(6,559)	(5,603)
Other non-segment revenues and expenses, net	$ 394	$ 588	$ 327	$ 663