Segment Reporting (Summary of Net Operating Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement [Line Items]
Straight-line rental income and expense, net			$ 16,763	$ 12,021
Equity in earnings of unconsolidated joint ventures	$ 5,552	$ 1,841	15,521	58,523
Promote income	0	0	0	20,007
Interest expense	(21,462)	(20,835)	(62,137)	(65,401)
Depreciation and amortization expense	(78,855)	(67,992)	(232,216)	(197,028)
Gain on sale of properties	(107)	21,952	194,741	93,339
Impairment Charges	0	(3,622)	0	(4,481)
Interest and other income, net	4,129	6,404	13,319	9,197
General and administrative expenses	(8,959)	(10,075)	(43,441)	(41,165)
Gain on land sales	3,915	5,665	7,221	8,449
Other operating expenses	(668)	(770)	(2,591)	(2,226)
Loss on extinguishment of debt	(89)	(16,568)	(240)	(26,104)
Income from continuing operations before income taxes	52,405	42,368	329,072	235,812
Operating Segments [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	143,009	117,899	411,206	346,915
Property Level Net Income, Cash Basis, Continuing Operations	142,878	123,385	419,031	365,062
Operating Segments [Member] | Industrial [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	142,247	117,307	408,843	344,080
Operating Segments [Member] | All Other Segments [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	762	592	2,363	2,835
Operating Segments [Member] | Service Operations [Member]
Statement [Line Items]
Earnings from Service Operations	1,256	1,138	5,160	4,115
Segment Reconciling Items [Member]
Statement [Line Items]
PNOI from sold properties included in continuing operations	(131)	5,486	7,825	18,147
Straight-line rental income and expense, net	5,832	4,341	16,763	9,547
Revenues Related to Lease Buyouts	0	491	23	10,348
Amortization of lease concessions and above and below market rents	593	(1,274)	1,599	(2,718)
Intercompany rents and other adjusting items	48	(108)	206	(478)
Corporate, Non-Segment [Member]
Statement [Line Items]
Equity in earnings of unconsolidated joint ventures	5,552	1,841	15,521	58,523
Promote income	0	0	0	20,007
Interest expense	(21,462)	(20,835)	(62,137)	(65,401)
Depreciation and amortization expense	(78,855)	(67,992)	(232,216)	(197,028)
Gain on sale of properties	(107)	21,952	194,741	93,339
Impairment Charges	0	(3,622)	0	(4,481)
Interest and other income, net	4,129	6,404	13,319	9,197
General and administrative expenses	(8,959)	(10,075)	(43,441)	(41,165)
Gain on land sales	3,915	5,665	7,221	8,449
Other operating expenses	(668)	(770)	(2,591)	(2,226)
Loss on extinguishment of debt	(89)	(16,568)	(240)	(26,104)
Other non-segment revenues and expenses, net	$ (1,658)	$ (1,605)	$ (3,887)	$ (3,174)