Schedule III: Real Estate and Accumulated Depreciation (Parenthetical) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) Property	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Real Estate and Accumulated Depreciation [Line Items]
Number of industrial properties | Property	440
Tenant improvements, useful life	Lease Term
Balance, Beginning of Year	$ 3,673,644	$ 3,495,745	$ 3,388,611
Acquisition of Real Estate Assets	148,660	162,769	168,517
Construction Costs and Improvements	289,877	190,383	137,361
Disposition of Real Estate Assets	(258,639)	(148,408)	(170,928)
Impairment of Real Estate	0	(2,756)	0
Write-off of Fully Depreciated and Other Assets	(23,333)	(24,089)	(27,816)
Balance, End of Year	3,830,209	3,673,644	3,495,745
Balance, Beginning of Year	811,784	789,919	797,919
Depreciation for Year	98,333	94,626	94,078
Disposition of Assets	(82,919)	(49,144)	(78,844)
Write-off of Fully Depreciated and Other Assets	(22,418)	(23,617)	(23,234)
Balance, End of Year	804,780	811,784	789,919
Balance, End of Year	$ 804,780	$ 811,784	$ 789,919
Buildings and Improvements | Minimum
Real Estate and Accumulated Depreciation [Line Items]
Property, plant and equipment, useful life	7 years
Buildings and Improvements | Maximum
Real Estate and Accumulated Depreciation [Line Items]
Property, plant and equipment, useful life	50 years
Land Improvements | Minimum
Real Estate and Accumulated Depreciation [Line Items]
Property, plant and equipment, useful life	3 years
Land Improvements | Maximum
Real Estate and Accumulated Depreciation [Line Items]
Property, plant and equipment, useful life	20 years