Investments in Properties - Dispositions (Details) - Portfolio Centers in Europe - Disposed of by Sale $ in Millions		3 Months Ended
	Mar. 16, 2021 USD ($) property	Mar. 31, 2021 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold	11
Purchase consideration | $	$ 680.0
Gain on sale | $		$ 333.3
Period of transitional property management services provided after closing on sale of real estate	1 year
UK
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold	4
Netherlands
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold	3
France
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold	3
Switzerland
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold	1