Segment Reporting (Summary of Net Operating Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement [Line Items]
Straight-line rental income and expense, net			$ 10,931	$ 7,722
Equity in earnings of unconsolidated joint ventures	$ 1,682	$ 51,933	9,969	56,682
Promote income	0	20,007	0	20,007
Interest expense	(20,675)	(21,680)	(40,675)	(44,566)
Depreciation and amortization expense	(75,832)	(67,013)	(153,361)	(129,036)
Gain on sale of properties	149,962	34,341	194,848	71,387
Impairment Charges	0	0	0	(859)
Interest and other income, net	4,727	2,260	9,190	2,792
General and administrative expenses	(13,459)	(11,858)	(34,482)	(31,090)
Gain on land sales	357	1,279	3,306	2,784
Other operating expenses	(1,137)	(718)	(1,923)	(1,457)
Loss on extinguishment of debt	(151)	(9,561)	(151)	(9,536)
Income from continuing operations before income taxes	192,814	124,620	276,667	193,442
Operating Segments [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	138,238	117,151	268,392	229,430
Property Level Net Income, Cash Basis, Continuing Operations	140,402	122,590	276,317	242,059
Operating Segments [Member] | Industrial [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	137,394	116,466	266,627	226,937
Operating Segments [Member] | All Other Segments [Member]
Statement [Line Items]
Property Level Net Operating Income – Cash Basis	844	685	1,765	2,493
Operating Segments [Member] | Service Operations [Member]
Statement [Line Items]
Earnings from Service Operations	3,212	1,202	3,904	2,977
Segment Reconciling Items [Member]
Statement [Line Items]
PNOI from sold properties included in continuing operations	2,164	5,439	7,925	12,629
Straight-line rental income and expense, net	4,642	3,628	10,931	5,205
Revenues Related to Lease Buyouts	0	72	23	9,857
Amortization of lease concessions and above and below market rents	461	(566)	1,006	(1,450)
Intercompany rents and other adjusting items	(20)	(310)	(6)	(745)
Corporate, Non-Segment [Member]
Statement [Line Items]
Equity in earnings of unconsolidated joint ventures	1,682	51,933	9,969	56,682
Promote income	0	20,007	0	20,007
Interest expense	(20,675)	(21,680)	(40,675)	(44,566)
Depreciation and amortization expense	(75,832)	(67,013)	(153,361)	(129,036)
Gain on sale of properties	149,962	34,341	194,848	71,387
Impairment Charges	0	0	0	(859)
Interest and other income, net	4,727	2,260	9,190	2,792
General and administrative expenses	(13,459)	(11,858)	(34,482)	(31,090)
Gain on land sales	357	1,279	3,306	2,784
Other operating expenses	(1,137)	(718)	(1,923)	(1,457)
Loss on extinguishment of debt	(151)	(9,561)	(151)	(9,536)
Other non-segment revenues and expenses, net	$ (1,357)	$ (986)	$ (2,229)	$ (1,569)