Rental Property - Disposals (Details) ft² in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) ft² building	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) ft² building	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings disposed | building	457		457
Area (in square feet) | ft²	91.8		91.8
Carrying value of property sold	$ 4,038,197,000		$ 4,038,197,000		$ 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	4		4
Area (in square feet) | ft²	1.2		1.2
Carrying value of property sold	$ 54,100,000		$ 54,100,000
Contribution to revenue	0	$ 1,100,000	0	$ 2,500,000
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	$ (49,000)	$ (35,000)	(200,000)	$ 400,000
Net proceeds from sales of rental property			101,900,000
Gain (Loss) on Sale			$ 47,800,000