Rental Property - Disposals (Details) ft² in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) ft² building	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) ft² building	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings disposed | building	462		462
Area (in square feet) | ft²	92.3		92.3
Carrying value of property sold	$ 4,050,955,000		$ 4,050,955,000		$ 3,998,507,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings disposed | building	5		5
Area (in square feet) | ft²	1.7		1.7
Carrying value of property sold	$ 64,400,000		$ 64,400,000
Contribution to revenue	100,000	$ 1,300,000	800,000	$ 4,500,000
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	$ (300,000)	$ (200,000)	(400,000)	$ 300,000
Net proceeds from sales of rental property			121,300,000
Gain (Loss) on Sale			$ 56,900,000