Investments in Real Estate - Schedule of Acquisitions Narrative (Details) $ in Thousands, £ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($) industry property_investment	Mar. 31, 2021 GBP (£) industry property_investment	Mar. 31, 2020 USD ($) industry property_investment	Mar. 31, 2020 GBP (£) industry property_investment
Real Estate [Line Items]
Number of investments in properties that caused any tenant to be 10% of more of total assets | property_investment	0	0	0	0
Value of properties acquired during the period	$ 1,027,802		$ 486,015
Rental revenue generated from acquisitions from investment grade tenants (as a percent)	39.00%	39.00%	36.00%	36.00%
New and under development
Real Estate [Line Items]
Acquired properties, percentage leased at the acquisition date (as a percent)	100.00%	100.00%	100.00%	100.00%
New properties
Real Estate [Line Items]
Value of properties acquired during the period	$ 969,871		$ 483,873
Number of industries in which tenants operate | industry	23	23	17	17
New properties | Retail
Real Estate [Line Items]
Property type acquired based on rental revenue (as a percent)	65.10%	65.10%	95.40%	95.40%
New properties | Industrial
Real Estate [Line Items]
Property type acquired based on rental revenue (as a percent)	34.90%	34.90%	4.60%	4.60%
New properties | U.K.
Real Estate [Line Items]
Value of properties acquired during the period	$ 402,962	£ 290.2	$ 165,573	£ 133.3