Investments in Real Estate - Acquisitions Footnotes (Details) $ in Thousands, £ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($) property	Sep. 30, 2021 GBP (£) property	Sep. 30, 2020 USD ($)	Sep. 30, 2020 GBP (£)
Real Estate [Line Items]
Settlement credits as reimbursement for acquired rent free period | $	$ 3,200
Number of properties related to settlement credits | property	35	35
Value of properties acquired during the period | $	$ 3,775,874		$ 1,298,853
Rental revenue generated from acquisitions from investment grade tenants (as a percent)	43.00%	43.00%	56.00%	56.00%
Properties under development
Real Estate [Line Items]
Number of properties, under development | property	50	50
Value of properties acquired during the period | $	$ 181,957
Retail
Real Estate [Line Items]
Property type acquired based on rental revenue (as a percent)	80.20%	80.20%	96.90%	96.90%
Industrial
Real Estate [Line Items]
Property type acquired based on rental revenue (as a percent)	19.80%	19.80%	3.10%	3.10%
U.K.
Real Estate [Line Items]
Value of properties acquired during the period | £				£ 356.7
U.K. | Properties under development
Real Estate [Line Items]
Number of properties, under development | property	1	1
Value of properties acquired during the period | £		£ 4.7